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Transcriber's notes

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[Illustration: FIG. 1]




  A
  PRACTICAL TREATISE
  ON
  GAS-LIGHT;
  EXHIBITING
  A SUMMARY DESCRIPTION
  OF THE
  APPARATUS AND MACHINERY
  BEST CALCULATED FOR
  ILLUMINATING
  STREETS, HOUSES, AND MANUFACTORIES,
  WITH
  CARBURETTED HYDROGEN, OR COAL-GAS,
  WITH REMARKS
  ON THE
  UTILITY, SAFETY, AND GENERAL NATURE OF THIS NEW BRANCH
  OF CIVIL ECONOMY.

  BY FREDRICK ACCUM,
  _OPERATIVE CHEMIST_,
  LECTURER ON PRACTICAL CHEMISTRY, ON MINERALOGY, AND ON CHEMISTRY
  APPLIED TO THE ARTS AND MANUFACTURES; MEMBER OF THE ROYAL
  IRISH ACADEMY, FELLOW OF THE LINNAEN SOCIETY, MEMBER
  OF THE ROYAL ACADEMY OF SCIENCES OF BERLIN, &c. &c.

  WITH SEVEN  PLATES.

  London:
  PRINTED BY G. HAYDEN, BRYDGES-STREET, COVENT GARDEN;
  FOR R. ACKERMANN, 101, STRAND;
  _LONGMAN, HURST, REES, ORME, AND BROWN; AND SHERWOOD, NEELY, AND
  JONES, PATERNOSTER ROW; AND J. HATCHARD, PICCADILLY_.

  _Price--Twelve Shillings in Boards._

  1815.


  EX FUMO DARE LUCEM.

  HOR.




PREFACE.


  _11, Compton Street Soho._

The following pages are intended to exhibit a summary view of the new
art of procuring light, by means of carburetted hydrogen gas obtained
from pit-coal, and which of late has been employed with unparalelled
success, as a substitute for candles and lamps, and is known by the name
of GAS-LIGHT.

To accomplish this object, I have given, in the first part of this
Essay, a concise and popular view of the chemical theory and production
of artificial light--I have explained the action of candles and lamps--I
have shown the methods of measuring the comparative illuminating power
of artificial light of different kinds, so as to appreciate their
economical value--I have stated the proportions of combustible materials
requisite for producing a light of a certain strength; with such other
preliminary facts and observations as were deemed necessary to enable
the reader to understand fully the nature of the new art of
illumination, which it is the object of this Essay to describe.

These positions are followed by a chemical view of the general nature
and composition of coal--the chemical changes which this substance
suffers, when employed in the production of gas-light--the different
products it furnishes--the modes of obtaining them--their properties and
applications in the various arts of life.

I have given a description of the apparatus and machinery by means of
which the coal-gas is prepared, and the methods employed for
distributing and applying it as a substitute for candles and lamps to
illuminate houses, streets and manufactories;--I have furnished the data
for calculating the expense that must attend the application of this
species of light under different circumstances, so as to determine the
relative cost or value of gas-lights, when compared with the lights now
in use--together with such other practical directions and facts as will
enable the reader to form a proper estimate of the gas-light
illumination, and to put this art into practice.

I have stated the leading objects of public and private utility to which
the new system of lighting may be successfully applied, candidly
pointing out those in which it cannot be made use of to advantage.

I have detailed the most obvious effects which the discovery of lighting
with coal-gas must inevitably produce upon the arts and upon domestic
economy; its primary advantages--its views--its limits, and the
resources it presents to industry and public economy. I have endeavoured
to show how far its application is safe, and in what respect it is
entitled to public approbation and national encouragement.

It may not be improper, before concluding, to inform the reader, that my
qualifications for the task I have undertaken are founded upon many
years experience, during which time, I possessed peculiar opportunities
to witness and verify the most extended series of operations that ever
have been made for the purpose of ascertaining the practicability,
safety, and general nature of the art of applying coal-gas as a
substitute for tallow and oil; and which have, as it were, fixed the
fate of this art. The numerous experiments I instituted, upon a large
scale, by desire of the Gas-Light Company, for the purpose of adducing
them in my evidence before the House of Commons, and House of Lords, on
a former occasion, have enabled me to collect such information as could
not have been obtained by other means. The substance of these results
(which are printed by order of Government,) are incorporated in this
Treatise, together with such other facts and observations as have
presented themselves in the routine of my profession elsewhere.

To generalize the results of my observations, and to make them
practically useful to the public, is the aim of the present publication,
and I need scarcely add, that their suffrages to the zeal and industry,
at least, with which I have endeavoured to attain my object, will be a
source of infinite satisfaction.

  FREDRICK ACCUM




Contents.


  INTRODUCTORY OBSERVATION.                                     Page  1.

  Progress of the arts.--Influence of it upon the morals and condition
  of man.--Beneficial tendency of chemical and mechanical improvements.
  --State of pre-eminence of people with regard to civilization.--How to
  be estimated.--Flourishing state of those nations which have shown the
  greatest activity in cultivating the useful arts, and establishing
  useful enterprises.--General observations on this subject.--Extra-
  ordinary discoveries of modern times.--New art of procuring light.--
  Object of the treatise.


  PART I.


  PRODUCTION OF ARTIFICIAL LIGHT, &c.                                 8.

  Production of the flame generated during the combustion of certain
  bodies.--Characters of flame when perfect.--Most luminous flame, how
  produced with the least consumption of combustible matter.--Conditions
  necessary for that purpose.--Importance of this subject, with regard
  to the production and supply of artificial light.--The flame of bodies
  may be tinged.--Blue flame, red flame, green flame, &c.--Opinion
  concerning the origin of light emitted by bodies burning with flame.--
  Philosophy of the subject.--Theory of the action of the instruments of
  illumination.--Rude method of procuring light employed in some
  countries.--Chemical action of candles, and lamps.--Agency of the
  tallow, oil, &c.--Office of the wick.--Reason why tallow candles
  require snuffing, and wax candles snuff themselves--Further
  observations on the subject.


  METHOD OF ASCERTAINING THE ILLUMINATING POWER OF CANDLES, LAMPS, AND
  OTHER LUMINOUS BODIES.                                             22.

  Optical principle assumed as law for determining the relative strength
  of lights of different kinds.--Admeasurement of the intensities of
  light.--Quantity of wax, tallow, oil, &c. requisite for producing a
  light of a certain strength.--Method of increasing the light of tallow
  candles, and to obviate the necessity of snuffing them.--A tallow
  candle placed in an inclined position gives more light than when
  placed perpendicularly and snuffed with an instrument.--Explanation of
  the fact.--Further observations on this subject.--Comparative cost of
  the light obtained by burning tallow candles of different sorts and
  sizes.


  PART II.


  GAS-LIGHT.                                                         47.

  Encouragement given by the legislature to the new system of procuring
  light.--Gas-light company, incorporated by charter, to apply the new
  art of illumination by way of experiment, on a large scale, to
  illuminate the streets and houses of the metropolis.--Power and
  authorities granted to this corporate body.--are very restricted, and
  do not prevent other individuals from entering into competition with
  them.--Boundaries of their experiments.--limit of capital employed by
  them.--Power of His Majesty with regard to the gas-light charter.


  THEORY OF THE COMBUSTION OF COAL IN ELUCIDATION OF THE NATURE OF GAS-
  LIGHT.                                                             49.

  Natural history of pit-coal.--Immediate constituent parts of coal.--
  Their relative quantities--are different in different kinds of coal.--
  Phenomena, which happen during the combustion of coal.--Analysis of
  coal by distillation.--Great waste of matter capable of producing
  light and heat, in the usual mode of burning coal.--Proofs of this
  statement.--Theory of the production of gas-light, compared with the
  production of light obtained by candles and lamps.--Place which the
  discovery of lighting with gas occupies in the philosophical order of
  knowledge.


  HISTORICAL SKETCH OF THE RISE AND PROGRESS OF THE APPLICATION OF COAL-
  GAS AS A SUBSTITUTE FOR PROCURING ARTIFICIAL LIGHT.                55.

  The discovery of the inflammable nature and application of coal-gas
  for the production of artificial light, cannot be claimed by any body
  now living.--Early notices of the inflammable property of the gas
  obtained by distilling coal.--Attempts to substitute it for tallow and
  oil.--Experiments made with coal-gas by Dr. CLAYTON, Dr. HALES, and
  the Bishop of Llandaff.--First successful attempt of lighting manu-
  factories with gas.--_Creditor_ and _debtor_ account concerning the
  expence of this mode of illumination, when compared with the light
  obtained by tallow candles.--Claims of Mr. MURDOCH with regard to the
  economical application of coal-gas.--Claims of Mr. WINSOR.--Experi-
  ments of Mr. NORTHERN, Mr. CLEGG, Mr. COOK, Mr. ACKERMANN.--Economical
  statements of the gas-light illumination when compared with the cost
  of the same quantity of light obtained by means of candles and lamps.


  THEORY OF THE PRODUCTION OF GAS-LIGHT; AND DESCRIPTION OF A PORTABLE
  APPARATUS FOR ILLUSTRATING, IN THE SMALL WAY, THE GENERAL NATURE OF
  THE NEW SYSTEM OF PROCURING LIGHT.                                 77.

  Philosophy of the production of coal-gas.--Characters of the various
  products which the gas-light process affords, their quantities, and
  modes of obtaining them.--Quantity of gas obtainable from a given
  weight of coal.--Illuminating power of a given bulk of coal-gas
  compared with the illuminating power of a given weight of tallow
  candles.--Practical directions with regard to the production of the
  gas from coal.--Its chemical constitution and analysis.--Pit-coal is
  not the only substance which affords carburetted hidrogen gas.--This
  gas exists ready formed in nature.--Mode of collecting it when found
  native.--Is given out by all kinds of vegetable matter, submitted to
  distillation in close vessels.--Other sources of obtaining this
  gazeous fluid.--Practical directions with regard to the method of
  obtaining from coal, this gazeous substance, as best suited for
  illumination.--Chemical constitution of coal-gas.--How ascertained.


  UTILITY OF THE GAS-LIGHT ILLUMINATION WITH REGARD TO PUBLIC AND
  PRIVATE ECONOMY.                                                   99.

  Objects to which the new system of lighting with gas may be
  beneficially applied.--Capital advantages of the gas-light illumina-
  tion.--Places and public edifices lighted with coal-gas in this metro-
  polis.--Situations best suited for the application of gas-lights.--
  places where it cannot be used to advantage.--Illumination of
  barracks, arsenals, dock yards, &c. with coal-gas.--Further observa-
  tions on this subject.--Great heat produced by gas-lights.--Reason why
  the flame of coal-gas produces more heat than the flame of candles and
  lamps.--Admeasurement of the comparative degrees of heat produced by
  gas-lights, oil lamps, tallow and wax candles, &c.--Gas lamps and
  burners, various kinds of.--Ornamental chandeliers and candelabras,
  for applying coal-gas as a substitute for oil.--Other products obtain-
  able from coal besides gas.--_Coke._--Its nature.--Combustion of it.--
  Produces a more strong and lasting heat than coal.--Explanation of
  this fact.--Advantages resulting from the use of coke as fuel.--Disad-
  vantages of its application in certain circumstances.--Relative effect
  of heat produced by equal quantities of coke and charcoal.--Method of
  measuring the comparative effect of different kinds of fuel in pro-
  ducing heat.--Capital advantages resulting from the application of
  coke, as fuel, in the art of burning lime.--Plaster of Paris, bricks,
  &c.--Quantity of coke obtainable from a certain quantity of pit-coal.
  --Kind of coke best suited for metallurgical operations.--Mode of
  obtaining it in the gas-light process.--Sort of coke best adapted for
  kitchen and parlour fires.--Manufacture of it.--_Coal tar._--How
  obtained.--Its properties.--Earl of Dundonald's method of manufac-
  turing tar from coal.--Quantity of coal-tar produced in the gas-light
  process from a given quantity of coal.--Characters of coal tar
  obtained from Newcastle coal, differ from that produced from canel
  coal.--_Coal pitch._--Process for obtaining it.--Properties of coal-
  pitch.--Use of it in the arts.--quantity of coal-pitch obtainable from
  a given quantity of tar.--_Ammoniacal liquor_ produced during the
  distillation of coal.--Its chemical constitution.--Quantity obtained
  from a given quantity of coal.--General observation respecting the
  scheme of applying coal-gas as a substitute for candles and lamps.--
  Effects which it must produce upon the arts and upon domestic economy.
  --Its views.--Primary advantages.--Resources which it presents to
  industry and public economy.--In what respect it is entitled to public
  approbation and national encouragement.--Effects of prejudice against
  the introduction of new and useful discoveries.--Have operated
  strongly in retarding the gas-light illumination.--Remarkable slowness
  with which improvements of extended utility make their way into common
  use, contrasted with the rapid adoption of fashionable changes.--Other
  causes unfavourable to the adoption of new and useful plans.--Further
  observations on this subject.--The new system of lighting with coal-
  gas can never supersede the use of candles and moveable lights.--Gas-
  light illumination cannot prove injurious to the Greenland fishery--
  nor can it diminish the coal trade--must prove beneficial to it.--The
  price of coal even when it is the highest cannot materially affect the
  beneficial application of gas-lights.--Striking advantages to be
  derived from the introduction of gas-lights into manufactories.--
  Principal expense which must always attend the gas-light illumination.
  --Is the dead capital employed for erecting the machinery.--Floating
  capital is small.--Advice to private individuals with regard to the
  erection of a gas-light apparatus calculated for their own use.--
  Expence which must attend the application of the new system of
  lighting under different circumstances.--Entire new scheme of
  illuminating streets, or small towns, with gas-lights; which would
  save all the main pipes for conveying the gas through the streets as
  well as the branch pipes which conduct the gas to the lamps.--Manage-
  ment of the gas-light machinery is extremely simple and easy.--The
  apparatus not liable to be out of order.--Observations on the safety
  of the gas-light illumination.--Misapprehension of the public con-
  cerning it.--Causes that have alarmed the public concerning the
  application of the new lights.--Gas-lights cannot give rise to those
  accidents which have so often arisen from the careless snuffing of
  candles, &c.--Produce no embers or sparks.--Cannot fall, or be dis-
  turbed without becoming extinguished.--Are the safest of all lights.--
  Impossibility of streets or towns lighted with gas to be thrown
  suddenly into darkness by the fracture of the gas-pipes conveying the
  gas to the lamps--or by the destruction of one or more of the gas-
  light machineries employed for preparing the gas.--Illustration
  showing the absurdity of such mistaken notions.--Curious self-ex-
  tinguishing lamp, invented by Mr. CLEGG.--His machine which measures
  and registers in the absence of the observer, the quantity of gas
  delivered by a pipe communicating with a gas-light _main_.--Leading
  characters of the new lights.--Objects and views which this art
  embraces.--It must lessen the consumption of oil.--Occasion a
  defalcation in the revenue.


  TABULAR VIEW, Exhibiting the quantity of GAS, COKE, TAR, PITCH,
  ESSENTIAL OIL, and AMMONIACAL LIQUOR, obtainable from a given quantity
  of COAL: together with an estimate of the quantity of Coal necessary
  to produce a quantity of Gas, capable of yielding a Light equal in
  duration of time and intensity to that produced by Tallow Candles of
  different kinds.                                                  164.


  DESCRIPTION OF THE GAS-LIGHT APPARATUS.                           166.

  METHOD of correcting the relative pressure of the Gasometer, so as to
  cause the gas which it contains to be uniformly of an equal density.
                                                                    181.


  DIRECTIONS TO WORKMEN ATTENDING THE GAS-LIGHT APPARATUS.          182.


  ESTIMATE of the price of a Gas-Light Apparatus.                   185.


  LONDON Price List of the most essential articles employed in the
  erection of a Gas-light Apparatus.                                186.




ERRATA.


  Page 24, line 11, _for_ too, _read_ two.
       48,      22, _for_ corporated, _read_ incorporated.
       53,       7, _for_ this combustion, _read_ the combustion.
       64,      24, _for_ CLEG, _read_ CLEGG.
    _ibid_      25, _for_ communicates, _read_ communicated.
       65,          erase the * and put it after the word CLEGG, line
                    24, p. 64.
    _ibid_      17, _for_ attemps, _read_ attempts.
      125,      23, _for_ degree, _read_ degrees.
      132,      25, _for_ coal, _read_ coal-tar.




DIRECTIONS TO THE BINDER:


  Plate I. facing the title; plate II. facing page 79; plate III. facing
  page 115; plate IV. facing page 119; plate V. facing page 120; and
  plates VI. and VII. at the end of the book.




  A
  PRACTICAL TREATISE
  ON
  GAS-LIGHT.




INTRODUCTORY OBSERVATION.


INFLUENCE OF THE PROGRESS OF THE ARTS UPON THE MORALS AND CONDITION OF
MAN.

It is an undoubted truth, that the successive improvements in the
condition of man, from a state of ignorance and barbarism, to that of
the highest cultivation and refinement, are usually effected by the aid
of machinery and expedients, calculated to procure the necessaries, the
comforts, and the elegancies of life; and that the pre-eminence of any
people in civilization is, and ought ever to be, estimated by the
proportional state of industry, and useful labour existing among them.

In proof of this great and striking truth, no other argument requires to
be offered, than an immediate reference to the experience of all ages
and places: the various nations of the earth, the provinces of each
nation, the towns, and even the villages of the same province, differ
from each other in their accommodations; and are in every respect more
flourishing, the greater their activity in establishing new channels of
useful employ, calculated to procure the necessaries and comforts of
life. Hence the nations which have shewn the most ingenuity in this way,
are not only the richest, but also the most populous and the best
defended: the provinces of those nations, are seen to flourish likewise
in proportion to their respective degrees of activity in this respect,
And from these exertions it is, as SMITH[1] emphatically remarks, that
"the accommodation of an European prince does not always so much exceed
that of an industrious and frugal peasant, as the accommodation of the
latter exceeds that of many an African king, the absolute master of the
lives and liberties of ten thousand naked savages."

  [1] Wealth of Nations, chap. 1.

It was a strange notion of Rousseau to maintain that mankind were
happier when they resembled wild beasts, than with all the expanded
knowledge of civilized life; and that the cultivation of their
understanding had tended to degenerate their virtues. There can be no
virtue but what is founded on a comprehensive estimate of the effects of
human actions, and an animal under the guidance of instinct can form no
such estimate.

The variety of production, of wants, and fabrication of a civilized
society, has given rise to barter or exchange; mutual supply has
increased the sub-division of labour, and improved the means of
conveyance. Streams, roads, ships, and carriages have extended their
beneficial intercourse; confidence between man and man has advanced the
moral principles of society, and afforded a progression, of which the
past gradation may indeed be traced, but to the future part of which
the imagination can scarcely form a probable outline. And as the moral
and physical powers of man expand, new resources and new agencies are
made subservient to our commands, which, in an earlier state of society,
would have appeared altogether visionary.

Who among the ancients would have listened to the extraordinary scheme
of writing books with such rapidity, that one man, by this new art,
should perform the work of twenty thousand amanuenses? What philosopher
would have given credit to the daring project of navigating the widest
ocean?--or imagined the astonishing effect of gun-powder--or the
extended application of the steam engine? What mortal would have dared
to dive to the bottom of the sea--or to soar aloft into the air--or bid
defiance to the thunder of the clouds? Discoveries which have changed,
as it were, the course of human affairs, and the effects of which have
already carried the intellectual operations of the human mind, to a
height they could by no other means have attained. The men of those
early ages, in the confidence of their own wisdom, might have derided
these discoveries as impossible, or rejected them as visionary; but to
those, who enjoy the full effects of such, and numerous other successful
inventions, it becomes a duty to reason upon different principles, and
to exert all means in their power to give effect to the progress of
useful knowledge.

The artificial production and supply of light during the absence of the
sun, unquestionably holds a distinguished rank among the most important
arts of civilized life.

If we could for a moment suppose the privation of artificial light, it
would follow as an immediate consequence that the greatest part of the
globe on which we dwell, would cease to be the habitation of man.
Whether he could ensnare or overtake those animals upon whose unprepared
remains he would then be compelled to feed--whether he might store the
fruits of the earth for his winter supply--what might be the physical
and moral consequences of a state of such desolation, may perhaps be
conjectured; but no estimate can show its dreadful magnitude. How much
do our comforts, and how greatly does the extent of our powers, in the
common affairs of life, depend upon the production and supply of
artificial light. The flame of a single candle animates a family, every
one follows his occupation, and no dread is felt of the darkness of
night. It might be a curious speculation to enquire how far, and in what
respects, the morals of men would become degraded by the want of this
contrivance. But it is sufficient on the present occasion, that,
previous to entering upon a dissertation respecting a new art of
illumination, a train of ideas has slightly been hinted at, which cannot
fail to show its magnitude and importance. The methods of procuring and
distributing light, during the absence of the sun, have not hitherto
attained the extent of their possible perfection: there is yet a wide
field for improvement in the construction of the instruments of
illumination, and the subject is highly deserving the attention of every
individual.

The scheme of lighting houses, streets, and manufactories, by means of
the inflammable gas, obtainable by distillation from common pit-coal,
professes to increase the wealth of the nation, by adding to the number
of its internal resources, and on this ground it is entitled, at least,
to a candid examination.

The apparent slight that has been thrown upon this new breach of civil
economy by some individuals, who appear to be incapable of judging of
its nature, has contributed to deter sensible and well disposed persons
from wishing it success. It is the more necessary to state this fact,
because, when a mistaken notion once becomes diffused, concerning the
nature of a new project, persons of the best intention are liable to
become affected with wrong impressions on their mind. I am neither a
share holder, nor a governor, nor am I directly or indirectly concerned
in any gas-light association.

The object of the succeeding pages, simply is to rescue the art of
illumination with coal-gas from misconception and misrepresentation, and
by a fair, and not overcharged statement of its merits and its
disadvantages, to appeal from prejudice and ignorance, to the good sense
of the community.




PART I.


PRODUCTION OF ARTIFICIAL LIGHT; AND THEORY OF THE ACTION OF CANDLES AND
LAMPS.

The flame of burning bodies consists of such inflammable matter in the
act of combustion as is capable of existing in a gazeous state. When all
circumstances are favorable to the complete combustion of the products,
the flame is perfect; if this is not the case, part of the combustible
body, capable of being converted into the gazeous state, passes through
the luminous flame unburnt, and exhibits the appearance of smoke. Soot
therefore always indicates an imperfect combustion. Hence flame is
produced from those inflammable substances only, which are either
totally volatile when heat is applied to them, so as not to alter their
chemical habitudes--or which contain a quantity of combustible matter
that is readily volatilized into vapour by heat, or the elements
necessary for producing such vapour or gazeous products, when the
chemical constitution of the body is altered by an increase of
temperature. And hence the flame of bodies is nothing else than the
inflammable product, either in a vaporous or in a permanently elastic
gazeous state. Thus originates the flame of wood and coal, when they are
burned in their crude state. They contain the elements of a quantity of
inflammable matter, which is capable of assuming the gazeous state by
the application of heat, and subsequent new chemical arrangements of
their constituent parts.

As the artificial light of lamps and candles is afforded by the flame
they exhibit, it seems a matter of considerable importance to society,
to ascertain how the most luminous flame may be produced with the least
consumption of combustible matter. There does not appear to be any
danger of error in concluding, that the light emitted will be greatest
when the matter is completely consumed in the shortest time. It is
therefore necessary, that the stream of volatilized combustible gazeous
matter should pass into the atmosphere with a certain determinate
velocity. If the quantity of this stream should not be duly
proportioned; that is to say, if it be too large, its internal parts
will not be completely burned for want of contact with the air. If its
temperature be below that of ignition, it will not, in many cases, burn
when it comes into the open air. And there is a certain velocity at
which the quantity of atmospherical air which comes in contact with the
vapour will be neither too great nor too small; for too much air will
diminish the temperature of the stream of combustible matter so much as
very considerably to impede the desired effect, and too little will
render the combustion languid.

We have an example of a flame too large in the mouths of the chimneys of
furnaces, where the luminous part is merely superficial, or of the
thickness of about an inch or two, according to circumstances, and the
internal part, though hot, will not set fire to paper passed into it
through an iron tube; the same defect of air preventing the combustion
of the paper, as prevented the interior fluid itself from burning. And
in the lamp of Argand we see the advantage of an internal current of
air, which renders the combustion perfect by the application of air on
both sides of a thin flame. So likewise a small flame is always whiter
and more luminous than a larger; and a short snuff of a candle giving
out less combustible matter in proportion to the circumambient air; the
quantity of light becomes increased to eight or ten times what a long
snuff would have afforded.

The light of bodies burning with flame, exists previously either
combined with the combustible body, or with the substance which supports
the combustion. We know that light exists in some bodies as a
constituent part, since it is disengaged from them when they enter into
new combinations, but we are unable to obtain in a separate state the
basis with which it was combined.

That in many cases the light evolved by artificial means is derived from
the combustible body, is obvious, if we recollect that the colour of
the light emitted during the process of combustion varies, and that this
variation usually depends not upon the medium which supports the process
of combustion, but upon the combustible body itself. Hence the colour of
the flame of certain combustibles, even of the purest kind may be tinged
by the admixture of various substances.

The flame of a common candle is far from being of an uniform colour. The
lowest part is always blue; and when the flame is sufficiently
elongated, so as to be just ready to smoke, the tip is red or brown.

As for the colours of flames that arise from coals, wood, and other
usual combustibles, their variety, which hardly amounts to a few shades
of red or purple, intermixed with the bright yellow light, seems
principally to arise from the greater or less admixture of aqueous
vapour, dense smoke, or, in short, of other incombustible products which
pass through the luminous flame unburnt.

Spirit of wine burns with a blueish flame. The flame of sulphur has
nearly the same tinge. The flame of zinc is of a bright greenish white.
The flame of most of the preparations of copper, or of the substances
with which they are mixed, is vivid green. Spirit of wine, mixed with
common salt, when set on fire, burns with a very unpleasant effect, as
may be experienced by looking at the spectators who are illuminated by
such light. If a spoonful of spirit of wine and a little boracic acid,
or nitrate of copper be stirred together in a cup, and then be set on
fire, the flame will be beautifully green. If spirit of wine be mixed
with nitrate of strontia, it will, afterwards, on being inflamed, burn
with a carmine red colour. Muriate of lime tinges the flame of burning
spirit of wine of an orange colour.[2]

  [2] See Chemical Amusement, comprising minute instructions for
  performing a series of striking and interesting chemical experiments,
  p. 8, &c.

Before we consider the general nature of Gas-Light, it will be necessary
to give a short sketch of the theory and action of the instruments of
illumination employed for supplying light, together with some other
facts connected with the artificial production and distribution of
light; such a proceeding will enable us to understand the general nature
of the new system of illumination which it is the object of this Essay
to explain.

To procure light for the ordinary purposes of life, we are acquainted
with no other ready means than the process of combustion.

The rude method of illumination consists, as is sufficiently known, in
successively burning certain masses of fuel in the solid state: common
fires answer this purpose in the apartments of houses, and in some
light-houses. Small fires of resinous wood, and the bituminous fossil,
called canel-coal, are in some countries applied to the same end, but
the most general and useful contrivance is that in which fat, or oil, of
an animal or vegetable kind is burned by means of a wick, and these
contrivances comprehend candles and lamps.

In the lamp the combustible substance must be one of those which retain
their fluidity at the ordinary temperature of the atmosphere. The candle
is formed of a material which is not fusible but at a temperature
considerably elevated.

All these substances must be rendered volatile before they can produce a
flame, but for this purpose it is sufficient to volatilize a small
quantity of any of them, successively; for this small quantity will
suffice to give a useful light, and hence we must admire the simple, yet
wonderful contrivance of a common candle or lamp. These bodies contain a
considerable quantity of the combustible substance, sufficient to last
several hours; they have likewise, in a particular place, a slender
piece of spongy vegetable substance, called the _wick_, which in fact is
the fire-place, or laboratory where the whole operation is conducted.

There are three articles which demand our attention in the lamp--the
oil, the wick, and the supply of air. It is required that the oil should
be readily inflammable; the office of the wick appears to be chiefly, if
not solely, to convey the oil by capillary attraction to the place of
combustion; as the oil is decomposed into carburetted hydrogen gas and
other products, other oil succeeds, and in this way a continual current
and maintenance of flame is effected.

When a candle is for the first time lighted, a degree of heat is given
to the wick, sufficient first to melt, and next to decompose the tallow
surrounding its lower surface; and just in this part the newly
generated gas and vapour is, by admixture with the air, converted into a
blue flame; which, almost instantaneously encompassing the whole body of
the vapour, communicates so much heat to it, as to make it emit a
yellowish white light. The tallow now liquefied, as fast as it boils
away at the top of the wick, is, by the capillary attraction of the same
wick, drawn up to supply the place of what is consumed by the cotton.
The congeries of capillary tubes, which form the wick, is black, because
it is converted into coal; a circumstance common to it with all other
vegetable and animal substances, when part of the carbon and hydrogen
which enter into their composition having been acted on by combustion,
the remainder and other fixed parts are by any means whatever covered
and defended from the action of the air. In this case, the burning
substance owes its protection to the surrounding flame. For when the
wick, by the continual wasting of the tallow, becomes too long to
support itself in a perpendicular situation, the top of it projects out
of the cone formed by the flame, and thus being exposed to the action of
the air, is ignited, loses its blackness, and is converted into ashes;
but that part of the combustible which is successively rendered volatile
by the heat of the flame is not all burnt, but part of it escapes in the
form of smoke through the middle of the flame, because that part cannot
come in contact with the oxygen of the surrounding atmosphere; hence it
follows, that with a large wick and a large flame, this waste of
combustible matter is proportionately much greater than with a small
wick and a small flame. In fact, when the wick is not greater than a
single thread of cotton, the flame, though very small, is, however,
peculiarly bright, and free from smoke; whereas in lamps, with very
large wicks, such as are often suspended before butchers' shops, or with
those of the lamp-lighters, the smoke is very offensive, and in great
measure eclipses the light of the flame.

A candle differs from a lamp in one very essential circumstance; viz.
that the oil or tallow is liquefied, only as it comes into the vicinity
of the combustion; and this fluid is retained in the hollow of the part,
which is still concrete, and forms a kind of cup. The wick, therefore,
should not, on this account, be too thin, because if this were the case,
it would not carry off the material as fast as it becomes fused; and the
consequence would be, that it would gutter or run down the sides of the
candle: and as this inconvenience arises from the fusibility of the
tallow it is plain that a more fusible candle will require a larger
wick; or that the wick of a wax candle may be made thinner than that of
one of tallow. The flame of a tallow candle will of course be yellow,
smoky, and obscure, except for a short time after snuffing. When a
candle with a thick wick is first lighted, and the wick snuffed short,
the flame is perfect and luminous, unless its diameter be very great; in
which last case, there is an opake part in the middle, where the
combustion is impeded for want of air. As the wick becomes longer, the
interval between its upper extremity and the apex of the flame is
diminished; and consequently the tallow which issues from that
extremity, having a less space of ignition to pass through, is less
completely burned, and passes off partly in smoke. This evil increases,
until at length the upper extremity of the wick projects beyond the
flame and forms a support for an accumulation of soot which is afforded
by the imperfect combustion, and which retains its figure, until, by the
descent of the flame, the external air can have access to the upper
extremity; but in this case, the requisite combustion which might snuff
it, is not effected; for the portion of tallow emitted by the long wick
is not only too large to be perfectly burned, but also carries off much
of the heat of the flame, while it assumes the elastic state. By this
diminished combustion, and increased afflux of half decomposed oil, a
portion of coal or soot is deposited on the upper part of the wick,
which gradually accumulates, and at length assumes the appearance of a
fungus. The candle then does not give more than one-tenth of the light
which the due combustion of its materials would produce; and, on this
account, tallow candles require continual snuffing. But if we direct our
attention to a wax candle, we find that as its wick lengthens, the light
indeed becomes less. The wick, however, being thin and flexible, does
not long occupy its place in the centre of the flame; neither does it,
even in that situation, enlarge the diameter of the flame, so as to
prevent the access of air to its internal part. When its length is too
great for the vertical position, it bends on one side; and its
extremity, coming in contact with air, is burned to ashes; excepting
such a portion as is defended by the continual afflux of melted wax,
which is volatilized, and completely burned, by the surrounding flame.
Hence it appears, that the difficult fusibility of wax renders it
practicable to burn a large quantity of fluid by means of a small wick,
and that this small wick, by turning on one side in consequence of its
flexibility, performs the operation of snuffing itself, in a much more
accurate manner than can ever be performed mechanically. From the above
statement it appears, that the important object to society of rendering
tallow candles equal to those of wax, does not at all depend on the
combustibility of the respective materials, but upon a mechanical
advantage in the cup, which is afforded by the inferior degree of
fusibility in the wax: and that, in order to obtain this valuable
object, one of the following effects must be produced: either the tallow
must be burned in a lamp, to avoid the gradual progression of the flame
along the wick; or some means must be devised to enable the candle to
snuff itself, as the wax-candle does; or the tallow itself must be
rendered less fusible by some chemical process. The object is, in a
commercial point of view, entitled to assiduous and extensive
investigation. Chemists in general suppose the hardness or less
fusibility of wax to arise from oxygen. Mr. NICHOLSON[3] is led by
various considerations to imagine, that the spontaneous snuffing of
candles made of tallow or other fusible materials, will scarcely be
effected but by the discovery of some material for the wick, which shall
be voluminous enough to absorb the tallow, and at the same time
sufficiently flexible to bend on one side.

  [3] Philosophical Journal, 4to Series, Vol. I. p. 70.


METHOD OF ASCERTAINING THE ILLUMINATING POWER OF CANDLES, LAMPS,
GAS-LIGHTS, AND OTHER LUMINOUS BODIES.

Though the eye is not fitted to judge of the proportional force of
different lights, it can distinguish, in many cases with great
precision, when two similar surfaces, presented together, are equally
illuminated. But as the lucid particles are darted in right lines, they
must spread uniformly, and hence their density will diminish in the
duplicate ratio of their distance. From the respective situations,
therefore, of the centres of divergency, when the contrasted surfaces
become equally bright, we may easily compute their relative degrees of
intensity.

For this purpose it is assumed as a principle, that the same quantity of
light, diverging in all directions from a luminous body, remains
undiminished in all distances from the centre of divergency. Thus we
must suppose, that the quantity of light falling on every body, is the
same as would have fallen on the places occupied by the shadow; and if
there were any doubt of the truth of the supposition, it might be
confirmed by some simple experiment. Therefore, it follows, that, since
the shadow of a square inch of any surface occupies at twice the
distance of the surface from the luminous point the space of four square
inches, the intensity of the light diminishes as the square of the
distance increases. If, consequently, we remove two sources of light to
such distances from an object that they may illuminate it in equal
degrees, we may conclude that their original intensities are inversely
as the squares of the distances.

Hence, if two lights of unequal illuminating powers shine upon the same
surface at equal obliquities, and an opake body be interposed between
them and the illuminated surface, the two shadows produced, must differ
in blackness or intensity in the same degree. For the shadow formed by
intercepting the greater light, will be illuminated by the smaller
light only, and reversely the other shadow will be illuminated by the
greater light: that is to say, the stronger light will be attended with
the deeper shadow. Now it is easy, by removing the stronger light to a
greater distance, to render the shadow which it produces at the common
surface equal to that afforded by the less. Experiments of this kind may
be conveniently made by fastening a sheet of white paper against the
wall of a room; the two lights, of whatever nature they are, intended to
be compared, must then be placed so that the ray of light from each
shall fall with nearly the same angle of incidence upon the middle of
the paper. In this situation, if a book or other object be held to
intercept part of the light which would have fallen on the paper, the
two shadows may be made to appear as in this figure;

[Illustration]

where A represents the surface illuminated by one of the lights only; B,
the surface illuminated by the other light; C, the perfect shadow from
which both lights are excluded. It will easily be understood that the
lights about D and E, near the angle F, will fall with equal incidences
when the double shadow is made to occupy the middle of the paper; and
consequently, if one or both of the lights be removed directly towards
or from the paper, as the appearances may require, until the two shadows
at E and D have the same intensity, the quantities of light emitted by
each will be as the squares of the distances from the paper. By some
experiments made in this way, the degree of illumination of different
lights may readily be ascertained to the tenth part of the whole. And,
by experiments of this kind, many useful particulars may be shewn. For,
since the cost and duration of candles, and the consumption of oil in
lamps, are easily ascertainable, it may be shewn whether more or less
light is obtained at the same expence during a given time, by burning a
number of small candles instead of one or more of greater thickness. It
will therefore be easy to compare the power of different kinds of lamps
or candles, or gas lights, so as to determine the relative cost of each
particular kind of the combustible substance employed for furnishing
light:--for example, if a candle and a gas-burner supplying coal-gas,
adjusted by a stop-cock, produce the same darkness of shadow, at the
same distance from the wall, the strength or intensity of light is the
same. An uniform degree of intensity of the gas-light may readily be
produced, by opening or shutting the stop-cock, if more or less be
required, and the candle is carefully snuffed to produce the most
regular and greatest quantity of light. The size of the flame in
experiments of this kind of course becomes unnecessary, and will vary
very much with the quality of the coal gas. The bulk of the gas
consumed, and the quantity of tallow used, by weighing the candle before
and after the experiment, furnish the data for ascertaining the relative
costs of tallow and gas-light, when compared with each other.

From experiments made by Count RUMFORD, concerning the quantity of
materials requisite for producing a light of a certain intensity for a
given time: it was found that we must burn of wax 100, of tallow 101, of
oil, in an Argand's lamp, 129, of an ill-snuffed tallow candle 229
parts, by weight. And with regard to the quantity of carburetted
hydrogen, or coal-gas, I have found that from 18 to 20 cubic feet
(according to the purity of the gas) are required to give a light equal
in duration and in illuminating powers to 1lb. of tallow candles, six to
the pound, provided they were set up and burnt out one after another.[4]

  [4] 112lbs. of Newcastle coal, called Tanfield Moor, produce, upon an
  average, from 250 to 300 cubic feet of gas, fit for illumination.


FURTHER ILLUSTRATIONS OF THE MODE OF COMPUTING THE RELATIVE COST OR
VALUE OF LIGHT, EMITTED BY MEANS OF CANDLES, LAMPS, & OTHER BODIES.

It is sufficiently known that the light of a candle, which is so
exceedingly brilliant when first snuffed, is very speedily diminished
to one-half and is usually not more than one-fifth or one-sixth before
the uneasiness of the eye induces us to snuff it.[5] Whence it follows,
that if candles could be made so as not to require snuffing, the average
quantity of light afforded by the same quantity of combustible matter
would be more than doubled.

  [5] Ezekiel Walker.--Nicholson's Journal, Vol. IV. 8vo. Series.

When a lighted candle is so placed as neither to require snuffing or
produce smoke, it is reasonable to conclude that the whole of the
combustible matter which is consumed is converted to the purpose of
generating light; and that the intensities of light afforded in a given
time, by candles of different dimensions, are in proportion to the
quantity of matter consumed. That is to say; when candles are made of
the same materials, if one candle produce twice as much light as
another, the former will in the same time lose twice as much weight as
the latter.

To prove the truth of this position, Mr. Walker made the experiments
contained in the following

TABLE.

  +-----------+--------+--------+-----------+--------+---------+
  |           |        |        |  Weight   |        |         |
  |           |        |        |  of the   |        |Distance |
  |  No. of   | No. of |Time of | Candles   |Strength| of the  |
  |    the    |   the  |burning.| consumed  |   of   | Candles |
  |Experiment.|Candles.|        |   in a    | Light. |from the |
  |           |        |        |   given   |        |  Wall.  |
  |           |        |        |   time.   |        |         |
  +-----------+--------+--------+-----------+--------+---------+
  |           |        |  h.    | oz.   dr. |        |  Feet.  |
  |          {|    1   |  3  0  | 0   15    |  1     |    7    |
  |   1      {|    3   |  3  0  | 1    1-1/2|  1 +   |    7    |
  |          {|  Mould |  3  0  | 0   15    |  1     |    7    |
  +-----------+--------+--------+-----------+--------+---------+
  |          {|    1   |  2 55  | 0   15    |  1     |    8    |
  |   2      {|    3   |  2 55  | 1    0    |  1 +   |    8    |
  |          {|  Mould |  2 55  | 0   15    |  1     |    8    |
  +-----------+--------+--------+-----------+--------+---------+
  |          {|    1   |  3  0  | 0   15-3/4|  1     |    8    |
  |   3      {|    3   |  3  0  | 1    2    |  1-1/8 |    8-3/4|
  |          {|  Mould |  3  0  | 0    0    |  1     |    9    |
  +-----------+--------+--------+-----------+--------+---------+
  |   4      {|    5   |  3  0  | 1    5    |  1.18  |    8-3/4|
  |          {|  Mould |  3  0  | 1    1-1/8|  1.    |    8    |
  +-----------+--------+--------+-----------+--------+---------+

These experiments, Mr. Walker informs us, were made in the following
manner:--

Three candles, the dimensions of which are given in the table, against
1, 3, and mould. These were first weighed, and then lighted at the same
instant. At the end of the time inserted in the third column of the
above table, they were extinguished and weighed again, and the loss of
weight of each candle is contained in the fourth column.

The three first experiments were made under such favourable
circumstance, that there was little doubt of their results being more
accurate than what practical utility requires, but the fourth experiment
cannot be depended on so much, in consequence of the variable light of
No. 5. This candle was moved so often to keep the two shadows equal,
that it was found necessary to set down its mean distance from the wall
by estimation; but as this was done before the candles were weighed, the
experimenter's mind could not be under the influence of partiality for a
system.

The method which Mr. Walker employed in comparing one light with another
in each experiment, was that which has been described page 24.

1. The experiments were made at different times, and the light of the
mould candle was made the standard, with which the lights of the others
were compared; but it must not be understood, that this candle gave the
same strength of light in every experiment.

2. The sign + in the 5th column, signifies that the candle against
which it is placed, gave a stronger light than the others.

From the experiments contained in the table, it appears to be an
established law, where combustion is complete, that the quantities of
light produced by tallow candles, are in the complicate ratio of their
times of burning and weights of matter consumed.

For if their quantities of matter be equal, and times of burning the
same, they will give equal quantities of light, _by the experiments_.

And if the times of burning be equal, the quantities of light will be
directly as their weights of matter expended.

Therefore the light is universally in the compound ratio of the time of
burning and weight of matter consumed.

If the law which Mr. Walker has endeavoured to prove, both by reason and
experiment, be admitted, we have a standard with which we may compare
the strength of any other light.

Let a small mould candle, when lighted, be so placed as neither to
produce smoke nor require snuffing, and it will lose an ounce of its
weight in three hours. Let this quantity of light produced under these
circumstances, be represented by 1.00.

Then should this candle at any other time, lose more or less of its
weight in three hours than an ounce, the quantity of light will be still
known, because the quantity of light in a given time is directly as the
weight of the candle consumed.[6]

  [6] To investigate rules for this purpose, 1. Let M represent the
  mould candle, _a_ its distance from the wall, on which the shadows
  were compared, _x_ its quantity of matter consumed in a given time,
  (_t_) and Q the quantity of light emitted by M in the same time: 2.
  Let _m_ represent any other candle, _b_ its distance from the same
  wall, and _y_ its quantity of matter consumed, in the time _t_.

  Then as the intensities of light are directly as the squares of the
  distances of the two candles from the wall, we have as _a_ squared : Q [::]
  _b_ squared : (_b_ squared + Q)/_a_ squared = the quantity of light, emitted by _m_ in the
  time.

  Then let us suppose that the quantities of light are directly as the
  quantities of matter consumed in the time _t_, and we have, As _x_ : Q
  [::] _y_ : (_y_ + Q)/_x_ = the quantity of light emitted by _m_ in
  that time, by hypothesis.

  Now, when (_b_ squared + Q)/_a_ squared (Theo. 1.) is = (Y + Q)/X (Theo. 2.) the
  quantities of light of M and _m_ are directly as their quantities of
  matter consumed in any given time.


METHOD OF INCREASING THE LIGHT OF TALLOW CANDLES, AND TO OBVIATE THE
NECESSITY OF SNUFFING THEM.

Mr. EZEKIEL WALKER has shewn that, if a trifling alteration be made in
the method of using common tallow candles, they will become excellent
substitutes for those of wax.

A common candle, weighing one-tenth of a pound, containing fourteen
single threads of fine cotton, placed so as to form an angle of 30
degrees[7] with the perpendicular, and lighted, requires no snuffing;
and what is much more valuable for some purposes, it gives a light that
is nearly uniform in strength without the least smoke. These effects are
thus produced:

  [7] Candlesticks may be made to hold the candle at this angle, or they
  may be so contrived as to hold the candle at any angle at pleasure.

When a candle burns in an inclined position, most part of the flame
rises perpendicularly from the upper side of the wick, and when viewed
in a certain direction, it appears in the form of an obtuse angled
triangle. And as the end of the wick projects beyond the flame at the
obtuse angle, it meets with the air, and is completely burnt to ashes:
hence it is rendered incapable of acting as a conductor to carry off
part of the combustible matter in the form of smoke. By this spontaneous
mode of snuffing, that part of the wick which is acted upon by the flame
continues of the same length, and the flame itself very nearly of the
same strength and magnitude[8].

  [8] The wick's not being uniformly twisted throughout, may occasion a
  little variation in the dimensions of the flame.

The advantages which may be derived from candles that require no
snuffing and afford no smoke, may be readily understood; but these
candles have another property which ought not to be passed over in
silence. A candle snuffed by an instrument gives a very fluctuating
light, which, in viewing near objects is highly injurious to the eye;
and this is an inconvenience which no shade can remove. But when a
candle is snuffed spontaneously, it gives a light so perfectly steady
and so uniformly bright, that the adjustments of the eye remain at rest,
and distinct vision is performed without pain, and without uneasiness.

Candles, on which Mr. WALKER has made experiments, are described in the
following

TABLE.

  +-----+--------------+---------+---------------+
  |     |No. of candles|         | No. of single |
  | No. | to the pound |Length in|threads of fine|
  |     | avoirdupoise | inches. | cotton in the |
  |     |   weight.    |         |    wick.      |
  +-----+--------------+---------+---------------+
  |  1  |      14      |   8.5   |     10        |
  |  2  |      13      |   9.    |     12        |
  |  3  |      10      |   9.74  |     14        |
  |  4  |       8      |  10.    |     20        |
  |  5  |       6      |  10.25  |     24        |
  |Mould|       6      |  13.    |               |
  +-----+--------------+---------+---------------+

Number 1, 2, and 3. These candles, when lighted and placed to form an
angle of 30 deg. with the perpendicular, require no snuffing: they give
lights which are nearly equal, and combustion proceeds so regularly,
that no part of the melted tallow escapes unconsumed, except from
accidental causes.

No. 4, placed at the angle mentioned above, and lighted, requires no
snuffing: it gives a light very little stronger than No. 1, but its
colour is not quite so white, nor its flame so steady.

No. 5. This candle, placed at an angle of 30 deg., and lighted, requires no
snuffing; its flame is rather fluctuating, and not so white as No. 4,
nor is its strength of light much greater than No. 1. The melted tallow
sometimes overflows when the air in the room is put in motion; yet the
light of this candle is much improved by being placed in an inclined
position.

The mould candle, treated in the same manner, affords a very pure steady
flame, without smoke and without snuffing, and its strength of light is
about equal to that of No. 1.

The experiments have not been sufficiently numerous to determine with
precision which of these candles affords the most light at a given
expence, but the few experiments which have been made seem to indicate,
that the quantity of light is nearly as the quantity of combustible
matter consumed, and thus a candle which is used in the manner pointed
out gives more light than a candle of the same dimension set
perpendicularly and snuffed, because one part of a candle that is
snuffed, is thrown away, and another part flies off in the form of
smoke. And this is not the only inconvenience that attends the using
candles in this manner, and which the other method is free from, for the
light which it gives is of a bad quality, on account of its being
variable and undulating.

From the time that a candle is snuffed till it wants snuffing again, its
strength of light scarcely continues the same for a single minute. And
that variation which frequently takes place in the height of the flame,
is a matter of still more serious consequence.

The flame of a long candle placed vertically when it is snuffed burns
steadily, is about two inches high, but it very frequently rises to the
height of four inches or upwards; drops down again in a moment, till it
is less than three inches, and then rises again. In this manner the
flame continues in motion for some time before it returns to its
original dimensions. But it does not continue long in a quiescent state
before it begins a new series of undulations. In this manner the candle
burns till the top of the wick is seen near the apex of the flame,
carrying off clouds of smoke. In this state of things the eye becomes
uneasy for want of light, and the snuffers are applied to remove the
inconvenience.

Mr. WALKER further observes, that it is these sudden changes, and not
the nature of candle-light itself, that do so much injury to the eye of
the student and artist; and that that injury may be easily prevented, by
laying aside the snuffers, and in the place of one large candle, let two
small ones be used in the manner stated.

The following observations on this subject are copied from the Monthly
Magazine, 1805, p. 206.

"It is scarcely necessary to observe, that the combustion of candles
proceeds the quicker in proportion as the inclination is greater. From
the experiments which I have made, I should consider an angle of forty
degrees with the perpendicular as the maximum of inclination, beyond
which several considerable inconveniencies would occur; and I should
take 25 degrees as the minimum of inclination, less than which does not
sufficiently expose the point of the wick to the action of the air.

"By those who are much in the habit of reading or writing by
candle-light, it will also be esteemed no inconsiderable addition to the
advantages already mentioned, that the trouble of seeking and applying
the snuffers is superseded. A candle of common size in a vertical
position, requires the application of the snuffers forty-five times
during its complete consumption.

"But I found an obstacle to the adoption of Mr. WALKER's plan, which,
from the inclined position of the candle, it did not immediately occur
to me by what means to counteract. Any agitation of the air of the room,
occasioned either by the opening or shutting of a door, or by the quick
passage of a person near the candle, caused the melted tallow to run
over, or, in more familiar language, caused the candle to gutter; which,
with the candle in this position, became an insuperable bar to the use
of it.

"For the prevention of this inconvenience, I have had a wire
skeleton-shade adapted to a rod bearing the same inclination as the
candle, and which at bottom joins the candlestick in an horizontal line
of about two inches, terminating in a nozzle fitting that of the
candlestick.--The distance of this rod from the candlestick, or, which
is the same thing, the length of the foot or horizontal line, is of
course to be determined by the distance between the two circles which
form the upper and lower apertures of the shade.--It may serve, perhaps,
more familiarly to describe this part of the apparatus, to state, that
it bears a perfect resemblance to the two first strokes of the written
figure 4; and the third stroke, if carried up as high as the first, and
made sloping instead of upright, will very well represent the situation
of the candle.

"When a strong light, for the purposes of reading or writing, be
required, a white silk or paper may be used, as is common, over the
skeleton; but when it be required that the light should be dispersed
over the room, a glass of a similar shape may be adopted, for the
purpose of preventing the flame from being influenced by any agitation
of the air of the room. If the upper circle of the shade be four inches
in diameter, the apex of the flame will be within it during more than
half the time of the complete consumption of the candle; the shade will
not, therefore, require adjusting for the purpose of preventing injury
to the silk, or whatever else may be used over the skeleton, more than
once during that time.

"Being myself much averse to the interruptions which a candle used in a
vertical position occasions, and which, though short, may, under some
circumstances, be highly vexatious, I wish to extend to others a benefit
which I prize rather highly."

Lord STANHOPE[9] has published a simple method of manufacturing candles,
which, according to his Lordship's statement, is superior to the method
usually employed. The principles upon which the process depends are the
following:--First, the wick of the candle is to have only three-fourths
of the usual number of cotton threads, if the candle be of wax or
spermaceti; and only two-thirds of the usual number, if the candle be of
tallow. Secondly, it is required that the wick in all cases be perfectly
free from moisture, a circumstance seldom attended to in the
manufacturing of candles; and thirdly, to deprive the wick of wax
candles, of all the air which is entangled in its fibres, and this may
conveniently be done, by boiling it in melted wax, till no more air
bubbles, or froth appear on the surface of the fluid.

  [9] Repository of Arts, Vol. I, p. 86.

If these circumstances be attended to, three candles of any size thus
prepared, last as long as four of the same size manufactured in the
common way. The light which they afford is superior and more steady than
the light of common candles; and lastly, candles made in this manner,
whether of wax, spermaceti, or tallow, do not require to be snuffed as
often. Besides all this, they flame much less, and are consequently
better for writing, reading, working and drawing, than candles made by
the common method.

The following observations will enable any person who is willing to try
the candles manufactured according to Lord Stanhope's plan, to ascertain
the real value of the improvements suggested by his Lordship. It shews
also the result of some experiments, made to ascertain the expence of
burning oil in lamps with wicks of various sizes.

A taper lamp, with eight threads of cotton, will consume in one hour
225/1000 oz. of spermaceti oil: at six shillings per gallon, the expence
of burning twelve hours is 13.71 farthings.

At seven shillings, it is 15.995 farthings.

At eight shillings, it is 18.280 farthings.

N. B. This gives as good a light as tallow candles of eight and ten in
the pound. This lamp seldom wants snuffing, and casts a steady and
strong light.

A taper, chamber, or watch lamp, with four ordinary threads of cotton in
the wick, consumes 1.664 oz. of spermaceti oil in one hour: the oil at
seven shillings per gallon, the expence of burning twelve hours, 7.02
farthings.

At eight shillings, it is 8.022 farthings.

At nine shillings, it is 9.024 farthings.

TABLE,

  Exhibiting a series of experiments, made with a view to determine the
  real and comparative expence of burning candles of different sorts and
  sizes.

  +-------+---------+-----------+--------+----------+-----------------+
  |       |Number of| Weight of |Time one|The time  |The expence in   |
  |       | candles |one candle.| candle |that one  |twelve hours when|
  |       | in one  |           | lasted.|pound will|candles are at   |
  |       | pound.  |           |        |last.     |12s. per dozen,  |
  |       |         |           |        |          |which also shews |
  |       |         |           |        |          |the proportion of|
  |       |         |           |        |          |expence at any   |
  |       |         |           |        |          |price, per dozen.|
  |       +---------+-----------+--------+----------+-----------------+
  |       |         |           |        |          |Farthings and    |
  |       |         | Oz.  Dr.  |Hr. Min.| Hr. Min. |hundredth parts. |
  |A small| 18-3/4  |  0  14    | 3   15 | 59   26  |     9.70        |
  |wick.  | 19      |  0  13-1/2| 2   40 | 50   34  |    11.40        |
  |A large| 16-1/2  |  0  15-1/2| 2   40 | 44    2  |    13.08        |
  |wick.  | 12      |  1   5-1/4| 3   27 | 41   24  |    13.92        |
  |       | 10-3/4  |  1   8    | 3   36 | 38   24  |    15.00        |
  |       |  7-3/4  |  2   1    | 4    9 | 32   12  |    17.88        |
  |       |  8      |  2   0    | 4   15 | 34    0  |    16.94        |
  |       |  5-3/4  |  2  13    | 5   19 | 30   15  |    19.06        |
  |       |Mould    |           |        |          |Moulds at 14d.   |
  |       |candles. |  Each.    |        |          | per dozen.      |
  |With   |  3-7/8  |  2  12    | 7   20 | 42   39  |    15.74        |
  |wax'd  |  4      |  4   0    | 9    3 | 36   20  |    18.56        |
  |wick.  |  3      |  5   2-3/4|17   30 | 52   30  |    16.825       |
  +-------+---------+-----------+--------+----------+-----------------+

The time each candle lasted, was taken from an average of several trials
on each size.

It has been suggested by Dr. FRANKLIN, that the flame of two candles
joined, gives a much stronger light than both of them separately. The
same, has been observed by Mr. WARREN, to be the case with flames of
gas-lights, which, when combined, give a much stronger light than they
would afford, when in a separate state.

Indeed, in all cases, where flames for producing light are placed near
to each other, it is always beneficial to preserve the heat of the flame
as much as possible. One of the most simple methods of doing this, is no
doubt, the placing of the several flames together, and as near as
possible to each other without touching, in order that they may mutually
cover and defend each other against the powerful cooling influence of
the surrounding cold bodies. This principle is now employed in the
Liverpool lamp, which acts by several flat or ribband wicks placed in
the form of a cylinder. The power of illumination of this lamp is
superior in effect and more economical than any other lamp in use--and
as flame is perfectly transparent to the light of another flame which
passes through it, there is no danger of loss of light on account of the
flames covering each other.




PART II.


GAS-LIGHT.


PRELIMINARY OBSERVATION.

A new art of procuring artificial light, which consists in burning the
gazeous fluid obtained by distillation from common pit-coal, has of late
engaged the attention of the public, under the name of _gas-light_.

The encouragement that has been given for some years past by the
legislature to this system of lighting, has induced certain individuals
to apply the coal-gas light for the illumination of streets, houses,
roads, and public edifices. And it is sufficiently known that a company
has been incorporated by charter under the name of the "_Gas Light and
Coke Company_," to apply this new art of procuring light, by way of
experiment, on a large scale, in lighting the streets of the
metropolis.[10]

  [10] An Act for granting certain powers and authorities to a company
  to be incorporated by charter, called the "Gas Light and Coke
  Company," for making inflammable air for the lighting of the streets
  of the metropolis, &c.--Session 1810, 50th Geo. III.

The power and authorities granted to this corporate body are very
restricted and moderate. The individuals composing it have no exclusive
privilege; their charter does not prevent other persons from entering
into competition with them. Their operations are confined to the
metropolis where they are bound to furnish not only a stronger and
better light to such streets and parishes as chuse to be lighted with
gas, but also at a cheaper price than shall be paid for lighting the
said streets with oil in the usual manner. The corporation is not
permitted to traffic in machinery for manufacturing or conveying the gas
into private houses, their capital or joint stock is limited to
200,000_l._ and His Majesty has the power of declaring the gas-light
charter void, if the company fail to fulfil the terms of it.


THEORY OF THE COMBUSTION OF COAL IN ELUCIDATION OF THE NATURE AND
PRODUCTION OF GAS LIGHT.

Pit-coal exists in this island in strata, which, as far as concerns many
hundred generations after us, may be pronounced inexhaustible; and is so
admirably adapted, both for domestic purposes and the uses of the arts,
that it is justly regarded as a most essential constituent of our
national wealth. Like all other bituminous substances, it is composed of
a fixed carbonaceous base or bitumen, united to more or less earthy and
saline matter constituting the ashes left behind when this substance is
burnt. The proportions of these parts differ considerably, in different
kinds of coal; and according to the prevalency of one or other of them,
so the coal is more or less combustible, and possesses the characters
of perfect pit-coal; and by various shades, passes from the most
inflammable canel-coal, into blind, Kilkenny, or stone-coal; and,
lastly, into a variety of earthy or stony substances; which, although
they are inflammable, do not merit the appellation of coal.

Every body knows that when pit-coals are burning in our grates, a flame
more or less luminous issues from them, and that they frequently emit
beautiful streams of flame remarkably bright. But besides the flame,
which is a peculiar gas in the state of combustion, heat expels from
coal an aqueous vapour, loaded with several kinds of ammoniacal salts, a
thick viscid fluid resembling tar, and some gases that are not of a
combustible nature. The consequence of which is, that the flame of a
coal-fire is continually wavering and changing, both in shape, as well
as brilliance and in colour, so that what one moment gave a beautiful
bright light, in the next, perhaps, is obscured by a stream of thick
smoke.

But if coals, instead of being suffered to burn in this way, are
submitted to distillation in close vessels, all its immediate
constituent parts may be collected. The bituminous part is melted out
in the form of tar. There is disengaged at the same time, a large
quantity of an aqueous fluid, contaminated with a portion of oil, and
various ammoniacal salts. A large quantity of carburetted hidrogen, and
other uninflammable gases, make their appearance, and the fixed base of
the coal remains behind in the distillatory apparatus in the form of a
carbonaceous substance, called coke.

All these products may be separately collected in different vessels. The
carburetted hidrogen, or coal-gas, may be freed from the non-inflammable
gases, and afterwards forced in streams out of small appertures, which,
when lighted, may serve as the flame of a candle to illuminate a room or
any other place. It is thus, that from pit-coal a native production of
this country, we may procure a pure, lasting, and copious light; which,
in other cases, must be derived from expensive materials, in part
imported from abroad.

It is chiefly upon the power of collecting the products afforded by
coal, with convenience and cheapness, that the promoters of the
gas-light illumination found their claims to public encouragement. They
conceive that the flame which pit-coal yields, as it is now consumed,
is turned to very little advantage: it is not only confined to one
place, where a red heat is more wanted than a brilliant flame, but it is
obscured, and sometimes entirely smothered, by the quantity of
incombustible materials that ascend along with it and pollute the
atmosphere.

That much inflammable matter is thus lost, is evident from facts that
come under our daily observation. We often see a flame suddenly burst
from the densest smoke, and as suddenly disappear; and if a light be
applied to the little jets that issue from the bituminous parts of the
coal, they will catch fire, and burn with a bright flame. A considerable
quantity of a gazeous fluid, capable of affording light and heat
continually escapes up the chimney, whilst another part is occasionally
ignited, and exhibits the phenomena of the flame and light of the fire.

The theory of the production of gas-light is therefore analogous to the
action of a lamp or candle. The wick of a candle being surrounded by the
flame, is in the same situation of the pit-coal exposed to distillation.
The office of the wick is chiefly to convey tallow, by capillary
attraction, to the place of combustion. As it is decomposed into
carburetted hidrogen gas it is consumed and flies off, another portion
succeeds; and in this way a continued current of tallow and maintenance
of flame are effected. See page 15.

The combustion of oil by means of a lamp depends on similar
circumstances. The tubes formed by the wick serve the same office as a
retort placed in a heated furnace through which the inflammable liquid
is transmitted. The oil is drawn up into these ignited tubes, and is
decomposed into carburetted hidrogen gas, and from the combustion of
this gas the illumination proceeds. See p. 15. What then does the
gas-light system attempt? Nothing more than to generate, by means of
sufficient furnaces and a reservoir of sufficient capacity, desired
quantities of the gas, which is the same material of the flame of
candles or lamps; and then by passing it through pipes to any desired
distance, to exhibit it there at the mouths of the conducting tubes, so
that it may be ignited for any desired purpose. The only difference
between this process and that of an ordinary candle or lamp, consists in
having the furnace at the manufactory, instead of its being in the wick
of the candle or lamp--in having the inflammable material distilled at
the station, instead of its present exhibitions in oil, wax, or tallow,
and then in transmitting the gas to any required distance, and igniting
it at the orifice of the conducting pipe instead of igniting it at the
apex of the wick. The principle is rational, and justified by the
universal mode in which all light is produced. Indeed, this discovery
ranks among the numerous recent applications of chemical science to the
purposes of life, which promise to be of the most general utility.

It is evident from the outline here given of the production and
application of coal-gas, that all the uses of pit-coal are not
exhausted; it will be sufficient to observe, that the complete analysis
of coal, which has been hitherto confined to the laboratory of the
chemist, requiring skill and nicety in the operator, and attended with
great trouble and expence, is now so far simplified, that many chaldrons
of coals may be decomposed by one gas-light apparatus in the space of
six hours, and all the component parts produced in their most useful
shape, at an expence out of all proportion below the value of the
products.


SKETCH OF THE RISE AND PROGRESS OF THE DISCOVERY AND APPLICATION OF
COAL-GAS, AS A SUBSTITUTE FOR PROCURING ARTIFICIAL LIGHT.

To assist the reader in comprehending the nature and object of
substituting coal-gas for tallow or oil, for the purpose of obtaining
light, it may be proper to touch slightly upon the successive
discoveries that have been made as to the decomposition of coal, and the
application of its different ingredients. Such a sketch will add to the
many examples that occur in the history of science and art, showing the
slow progress of mankind in following up known principles, or extracting
from acknowledged facts every possible advantage.

In the Philosophical Transactions of the Royal Society, V. XLI. so long
ago as the year 1739, is recorded a paper, exhibiting an account of some
experiments made by Dr. James Clayton, from which it appears that the
inflammable nature of coal-gas was then already known. Dr. Clayton
having distilled Newcastle coal, obtained, as products of the process,
an aqueous fluid, a black oil, and an inflammable gas, which he caught
in bladders, and by pricking these he was enabled to inflame the gas at
pleasure.

It is further known, that in the beginning of the last century, Dr.
Hales[11] on submitting pit-coal to a chemical examination, found, that
during the ignition of this fossil in close vessels, nearly one-third of
the coal became volatilized in the form of an inflammable vapour. Hence
the discovery of the inflammable nature of coal-gas can no longer be
claimed by any person now living.

  [11] Vegetab. Statics, vol. I.

In the year 1767, the Bishop of Llandaff[12] examined the nature of the
vapour and gazeous products evolved during the distillation of pit-coal.
This learned philosopher noticed, that the volatile product is not only
inflammable as it issues from the distillatory vessel, but that it also
retained its inflammability after having been made to pass through
water, and suffered to ascend through two high curved tubes. The solid
matters obtained by this venerable prelate, were, an aqueous ammoniacal
fluid, a tenaceous oil, resembling tar, an ammoniacal liquor, and a
spongy coal, or coke.

  [12] Watson's Chemical Essays, vol. II.

The first discovery and application of the use of coal-gas for the
purpose of illumination is claimed by Mr. Murdoch.

Dr. W. Henry of Manchester, has published the following account[13] of
this discovery.

  [13] Thompson's System of Chemistry, vol. I. p. 52.

"In the year 1792, at which time Mr. Murdoch resided at Redruth, in
Cornwall, he commenced a series of experiments upon the quantity and
quality of the gases contained in different substances. In the course of
these he remarked, that the gas obtained by distillation from coal,
peat, wood, and other inflammable substances, burnt with great
brilliancy upon being set fire to; and it occurred to him, that by
confining and conducting it through tubes, it might be employed as an
economical substitute for lamps and candles. The distillation was
performed in iron retorts, and the gas conducted through tinned iron and
copper tubes to the distance of 70 feet. At this termination, as well as
at intermediate points, the gas was set fire to, as it passed through
apertures of different diameters and forms, purposely varied with a view
of ascertaining which would answer best. In some the gas issued through
a number of small holes like the head of a watering pan; in others it
was thrown out in thin long sheets; and again in others in circular
ones, upon the principle of Argand's lamp. Bags of leather and of
varnished silk, bladders, and vessels of tinned iron, were filled with
the gas, which was set fire to, and carried about from room to room,
with a view of ascertaining how far it could be made to answer the
purpose of a moveable or transferable light. Trials were likewise made
of the different quantities and qualities of gas produced by coals of
various descriptions, such as the Swansea, Haverfordwest, Newcastle,
Shropshire, Staffordshire, and some kinds of Scotch coals.

"Mr. Murdoch's constant occupations prevented his giving farther
attention to the subject at that time; but he again availed himself of a
moment of leisure to repeat his experiments upon coal and peat at Old
Cumnock, in Ayrshire, in 1797; and it may be proper to notice that both
these, and the former ones, were exhibited to numerous spectators, who,
if necessary, can attest them. In 1798, he constructed an apparatus at
Soho Foundry, which was applied during many successive nights to the
lighting of the building; when the experiments upon different apertures
were repeated and extended upon a large scale. Various methods were also
practised of washing and purifying the air, to get rid of the smoke and
smell. These experiments were continued, with occasional interruptions,
until the epoch of the peace in the spring of 1802, when the
illumination of the Soho manufactory afforded an opportunity of making a
public display of the new lights; and they were made to constitute a
principal feature in that exhibition."

In the year 1803 and 1804, Mr. Winsor exhibited at the Lyceum in London
the general nature of this new mode of illumination though the
machinery for procuring, and the manner of purifying the gas, he kept a
secret. He exhibited the mode of conducting the gas through the house,
and a number of devices for chandeliers, lamps, and burners, by which it
might be applied. Among these he proposed long flexible tubes suspended
from the ceiling, or wall of the room, and at the end communicating with
burners or lamps of different kinds. This gentleman showed also by
experiment, that the flame of the gas-light, produced no smoke; that it
was not so dangerous as the flame of candles or lamps; that it could not
produce sparks; and that it was not so readily extinguished by gusts of
wind or torrents of rain.

Mr. WINSOR's display of gas-lights took place more than two years before
Mr. MURDOCH's priority of right was heard of.

In stating these facts I do not mean to say that Mr. MURDOCH derived the
hint of applying the coal-gas from the previous exhibition of Mr.
WINSOR, because it is quite within the bounds of probability that the
ideas of Mr. MURDOCH may have arisen totally independent of all
acquaintance with Mr. WINSOR's.

The claims of invention, or the determination of the right of priority,
concerns the public only so far as the honour and estimation of any
useful discovery conferred on the inventor may induce other individuals
to devote their talents to similar pursuits; by means of which, more
discoveries may be made, and the subject of human invention become
extended, or rendered more useful. For as the mere benefits which
mankind may derive from any particular discovery, they are certainly
more indebted to the person who first applied the discovery to actual
practice, than to him who first made it, and merely illustrated it by
barren experiments. Mr. WINSOR certainly pressed on the mind of the
public with unremitted perseverance and diligence the extensive
application of gas-light in the year 1802, but he made no new discovery
with regard to the composition of coal; he did not even invent the mode
of conducting the gas through tubes; and if he has pointed out the
particulars of the process, he has made a very important, though not the
most brilliant improvement in this line of business. Mr. WINSOR's
publications are, perhaps, but ill adapted to promote his cause; and the
exaggerated calculation which the sanguine mind of a discoverer is
naturally disposed to indulge in, have, to superficial observers, thrown
an air of ridicule and improbability on the whole scheme of lighting
with gas.

It may, however, be safely affirmed, that if the same facts had come
forward, under the sanction of some great name in the chemical or
philosophical world, the public incredulity would long since have been
subdued; and the plan, which for many years has been struggling for
existence, would have been eagerly adopted as a national object.

On the 18th of May, 1804, Mr. FREDERICK ALBERT WINSOR, took out a patent
for combining the saving and purifying of the inflammable gas (for
producing light and heat), the ammonia, tar, and other products of
pit-coal, with the manufacture of a superior kind of coke (see
Repertory, 2d Series, v. 172). And, lately, the same gentleman has taken
out a second patent, for further improvements in these processes.

In the year 1805, Mr. NORTHERN, of Leeds, also directed the attention
of the public to the application of coal-gas, as a substitute for tallow
light, as will be seen by the following extract of the Monthly Magazine
for April, 1805.

"I distilled in a retort, 50 ounces of pit-coal in a red heat, which
gave 6 ounces of a liquid matter covered with oil, more or less fluid as
the heat was increased or diminished. About 26 ounces of cinder remained
in the retort; the rest came over in the form of air, as it was
collected in the pneumatic apparatus. I mixed part of it with
atmospherical air, and fired it with the electric spark with a tolerable
explosion, which proves it to be hydrogene.--Whether any of the other
gases were mixed with it, I did not then determine. In the receiver I
found a fluid of an acid taste, with a great quantity of oil, and, at
the bottom, a substance resembling tar.

"The apparatus I make use of for producing light is a refiner's
crucible, the top of which (after filling with coal) I close with a
metal cover, luted with clay or other luting, so as to prevent the
escape of the gas; a metal pipe is soldered into the cover, bent so as
to come under the shelf in the pneumatic trough, over which I place a
jar with a stop-cock and a small tube; the jar being previously filled
with water, the crucible I place on the common or other fire as is most
convenient; and as the heat increases in it, the gas is forced rapidly
through the water into the jar, and regularly displaces it. I then open
the cock and put fire to the gas, which makes its escape through the
small tube, and immediately a most beautiful flame ensues, perfectly
free from smoke or smell of any kind. A larger light, but not so vivid
or clear, will be produced without passing the gas through water, but
attended with a smoke somewhat greater than that of a lamp charged with
common oil.

"I have great hopes that some active mechanic or chemist will, in the
end, hit on a plan to produce light for large factories, and other
purposes, at a much less expence, by the above or similar means, than is
at present produced from oil."

Soon afterwards, Mr. SAMUEL CLEGG[14] of Manchester, Engineer,
communicated an account of his method of lighting up manufactories with
gas-light to the Society of Arts, for which he received the silver
medal.

  [14] This gentleman is at present engineer to the Gas-Light Company.

Since that time, the application of gas-light has spread rapidly, and
numerous manufactories and other establishments have been lighted by
coal-gas.

In France, the application of gas-lights to economical purposes, was
pointed out long before it was publicly introduced into this country. M.
LE BON had a house fitted up in Paris, in the winter of 1802, so as to
be entirely illuminated by gas-lights, which was seen by thousands with
admiration; and had a _brevet d'invention_ (patent) granted to him by
the French government, for the art of producing light from wood, ignited
in close vessels.

Many other attempts have been made to derive advantage from the
different ingredients of coal; but they are too obscure to merit
particular enumeration.

In the year 1808, Mr. MURDOCH presented to the Royal Society his account
of the application of gas-light, and was complimented with Count
ROMFORD's medal for the same.

The following statement is taken from Mr. MURDOCH's paper.

"The whole of the rooms of the cotton mill of Mr. LEE, at Manchester,
which is I believe the most extensive in the United Kingdom, as well as
its counting-houses and store-rooms, and the adjacent dwelling house of
Mr. LEE, are lighted with the gas from coal. The total quantity of light
used during the hours of burning has been ascertained, by a comparison
of shadows, (_see page 23_) to be about equal to the light which 2500
mould candles, of six to the pound, would give; each of the candles with
which the comparison was made consuming at the rate of 4-10ths of an
ounce (175 grains) of tallow per hour.

"The gas-burners are of two kinds: the one is upon the principle of the
Argand lamp, and resembles it in appearance; the other is a small curved
tube with a conical end, having three circular apertures or
perforations, of about a thirtieth of an inch in diameter, one at the
point of the cone, and two lateral ones, through which the gas issues,
forming three divergent jets of flame, somewhat like a fleur-de-lis. The
shape and general appearance of this tube has procured it, among the
workmen, the name of the cockspur burner.

"The number of burners employed in all the buildings amounts to 271
Argand, and 653 cockspurs, each of the former giving a light equal to
that of four candles of the description above-mentioned; and each of the
latter a light equal to two and a quarter of the same candles; making
therefore the total of the gas-light a little more than equal to that of
2500 candles, six to the pound. When thus regulated, the whole of the
above burners require an hourly supply of 1250 cubic feet of the gas
produced from cannel-coal; the superior quality and quantity of the gas
produced from that material having given it a decided preference in this
situation over every other coal, notwithstanding its higher price.

"The time during which the gas-light is used may, upon an average of the
whole year, be stated at least at two hours per day of 24 hours. In some
mills, where there is over work, it will be three hours; and in the few
where night work is still continued nearly 12 hours. But taking two
hours per day as the common average throughout the year, the consumption
in Messrs. Philips and Lee's mill will be 1250 x 2 = 2500 cubic feet of
gas per day; to produce which 700 weight of cannel-coal is required in
the retort. The price of the best Wiggan cannel-coal (the sort used) is
13-1/2_d._ per cwt. (22_s._ 6_d._ per ton) delivered at the mill, or say
about eight shillings for the seven hundred weight. Multiplying by the
number of working days in the year (313,) the annual consumption of coal
will be 110 tons, and its cost 125_l._

"About one-third of the above quantity, or say forty tons of good common
coal, value ten shillings per ton, is required for fuel to heat the
retorts, the annual amount of which is 20_l._

"The 110 tons of cannel-coal, when distilled, produce about 70 tons of
good coke, which is sold upon the spot at 1_s._ 4_d._ per cwt. and will
therefore amount annually to the sum of 93_l._

"The quantity of tar produced from each ton of cannel-coal is from 11 to
12 ale gallons, making a total annual produce of about 1250 ale gallons,
which not having been yet sold, it cannot yet be determined its value.

"The interest of the capital expended in the necessary apparatus and
buildings, together with what is considered as an ample allowance for
wear and tear, is stated by Mr. LEE at about 550_l._ per annum, in which
some allowance is made for this apparatus being made upon a scale
adequate to the supply of a still greater quantity of light, than he has
occasion to make use of.

"Mr. LEE is of opinion that the cost of attendance upon candles would be
as much, if not more, than upon the gas apparatus; so that, in forming
the comparison, nothing need be stated upon that score, on either side.

"The economical statement for one year, then, stands thus:

  Cost of 110 tons of cannel coal                                  L 125

  Ditto of 40 tons of common ditto, to carbonise                      20
                                                                    ----
                                                              In all 145
                                                                    ----
  Deduct the value of 70 tons of coke                                 93

  The annual expenditure in coal, after deducting the value of the
  coke, and without allowing any thing for the tar, is therefore      52

  And the interest of capital sunk, and wear and tear of apparatus   550

  Making the total expence of the gas apparatus per annum, about     600

"That of candles, to give the same light, would be about 2000_l._ For
each candle, consuming at the rate of 4-10ths of an ounce of tallow per
hour, the 2500 candles burning, upon an average of the year, two hours
per day, would, at one shilling per pound, the present price, amount to
nearly the sum of money above-mentioned.

"If the comparison were made upon an average of three hours per day, as
in most cases, would perhaps be nearer to the truth, and the tear and
wear remaining nearly the same as on the former case, the whole cost
would not exceed 650_l._ while that of the tallow would be 3000_l._"

Mr. ACKERMAN in this metropolis, has shown that the art of gas-light
illumination is not confined to great manufactories, but that its
advantages are equally applicable to those on a moderate scale. The
whole of Mr. ACKERMAN's establishment, his public library, warehouse,
printing-offices and work-shops, together with his dwelling house, from
the kitchen to the drawing-room, has, for these four years past, been
lighted with gas, to the total exclusion of all other lights. The result
of the whole of this proceeding will be obvious from the following
letter:

  To MR. ACCUM.

  SIR,

  "In answer to your request with regard to my gas-lights, which I now
  have in my house, I take this mode of informing you, that I charge two
  retorts with 240lbs. of coal, half cannel and half Newcastle, from
  which I extract 1000 cubic feet of gas. To obtain this quantity of
  gas, when the retorts are cold, I use from 100 to 110lb. of common
  coals; but when they are in a working state, that is to say, when they
  are once red hot, the carbonising fuel amounts to about 25lb. per
  retort. The bulk of gas thus obtained supplies 40 Argand's lamps, of
  the large size, for four hours per night, during the long winter
  evenings, together with eight Argand's lamps and about 22 single
  cockspur burners, for three hours per night: in addition to which my
  printers employ 16 cockspur burners for ten hours per day to heat
  their plates instead of charcoal fire. In the depth of winter we
  charge two retorts per day: but, upon an average, we work 365 retorts
  in 365 days.

  Now 365 retorts containing 120lb. of coal each, make 43800lb. which is
  equal to ten chaldrons of Newcastle and eight tons of cannel coal.

  10 chaldrons of Newcastle coals, at 65s. make              L 32  10  0
   8 tons of cannel coal,[15] (this coal is sold by weight)
     at 100s. per ton                                          40   0  0
   7 chaldrons of common coals for carbonising, at 55s.        19   5  0
  To wages paid the servant for attending the gas apparatus    30   0  0
  Interest of money sunk                                       30   0  0
  The wear and tear of the gas-light apparatus I consider to
  be equal to the wear and tear of lamps, candlesticks, &c.
  employed for oil, tallow, &c.                              -----------
                      Total expence of the gas lights         151  15  0

  DEDUCT

  23 chaldrons of coke, at 60s. per chaldron         69
  Ammoniacal liquor                                   5
  Tar                                                 6
  Charcoal employed by the copper-plate printers to
  heat their plates, which is now done with the gas-
  light flame, cost, annua                           25
  Two chaldrons of coals _minus_ used as fuel, for
  warming the house, since the adoption of the gas-
  lights, at 65s. per chaldron                        6  10
                                                     ------   111  10  0
                                                              ----------
                      Nett expences of the gas-lights        L 40   5  0
                                                              ----------
  The lights used in my Establishment, prior to the gas-
  lights, amounted annually to                                160   0  0
  My present system of lighting with gas costs, per ann.       40   5  0
                                                              ----------
             Balance in favor of the gas for one year       L 119  15  0

  Such is the simple statement of my present system of lighting, the
  brilliancy of which, when contrasted with our former lights, bears the
  same comparison to them as a bright summer sun-shine does to a murky
  November day: nor are we, as formerly, almost suffocated with the
  effluvia of charcoal and fumes of candles and lamps. In addition to
  this, the damage sustained by the spilling of oil and tallow upon
  prints, drawings, books and paper, &c. amounted annually to upwards of
  50l. All the workmen employed in my establishment consider their
  gas-lights as the greatest blessing; and I have only to add, that the
  light we now enjoy, were it to be produced by means of Argand's lamps
  or candles, would cost at least 350l. per annum.

  I am, with respect,

  Yours,

  Strand, March 13,

  1815.

  R. ACKERMAN."

  [15] _Although cannel-coal sells at nearly double the price of
  Newcastle coal, I use it in preference to the latter, because it
  affords a larger portion of gas, and gives a much more brilliant
  light._

Another manufacturer who was one of the first that adopted the use of
this method of illumination in the small way, and who gave a statement
of its advantages to the public, is Mr. COOK, a manufacturer of metal
toys, at Birmingham, a clear-headed, prudent man, not apt to be dazzled
by a fanciful speculation, but governed in his transactions by a simple
balance of profit and loss. There is a _naivete_ in his own account of
the process which will amuse as well as instruct the reader.

"My apparatus is simply a small cast-iron pot, of about eight gallons,
with a cast-iron cover, which I lute to it with sand. Into this pot I
put my coal. I pass the gas through water into the gasometer or
reservoir, which holds about 400 gallons; and, by means of old
gun-barrels, convey it all round my shops. Now, from twenty or
twenty-five pounds of coal, I make perhaps six hundred gallons[16] of
gas; for, when my reservoir is full, we are forced to burn away the
overplus in waste, unless we have work to use it as it is made: but, in
general, we go on making and using it, so that I cannot tell to fifty or
a hundred gallons;--and, in fact, a great deal depends on the coals,
some coals making much more than others. These twenty-five pounds of
coal put into the retort, and say twenty-five pounds more to heat the
retort, which is more than it does take one time with another, but I am
willing to say the utmost, are worth four-pence per day. From this
four-pence we burn eighteen or twenty lights during the winter season."

  [16] A wine-gallon is equal to 231 cubic inches.

Thus are the candles which Mr. COOK used to employ, and which cost him
three shillings a day, entirely superseded. But, besides his expence in
candles, oil and cotton for soldering, used to cost him full 30_l._ a
year; which is entirely saved, as he now does all his soldering by the
gas flame only. For "in all trades in which the blow-pipe is used with
oil and cotton, or where charcoal is employed to produce a moderate
heat, the gas flame will be found much superior, both as to quickness
and neatness in the work: the flame is sharper, and is constantly ready
for use; while, with oil and cotton or charcoal, the workman is always
obliged to wait for his lamp or coal getting up; that is, till it is
sufficiently on fire to do his work. Thus, a great quantity of oil is
always burned away useless; but, with the gas, the moment the stop-cock
is turned, the lamp is ready, and not a moment is lost." We must refer
to Mr. COOK's letter for the details of expence, which he gives with
faithful minuteness, and always leaning to the side unfavourable to the
gas. The result of the whole is, that he saves 30_l._ out of the 50_l._
which his lights formerly cost him: and, when we consider that his
calculation allows the gas-lights to burn the whole year, and the
candles only twenty weeks, there can be little doubt, that the savings
in this case follow nearly the same proportion as in the former. If the
apparatus be erected even on a smaller scale, "the saving," Mr. COOK
assures us, "will still be considerable: for the poor man, who lights
only six candles, or uses one lamp, if the apparatus is put up in the
cheapest way possible, will find it only cost him 10_l._ or 12_l._ which
he will nearly, if not quite, save the first year."

Mr. ACKERMAN having, in this town, set the example of lighting his
establishment with gas, several other individuals soon followed the
attempt. The following statement will show, that this species of light
may be made use of with the greatest advantage, upon a still smaller
scale, where no great nicety with regard to the apparatus for procuring
gas is required. The following report I have received from Messrs.
LLOYD, of Queen Street, Southwark, thimble manufacturers and
whitesmiths, who have used the gas-light for soldering and other
purposes these five years past.

  From 4 pecks or 1 bushel of coals, weighing 69lbs. for
  which we now pay (1809) 1s. we produce 4-3/4 pecks of
  coke and 1/2 peck of coal not carbonised remains in the
  distilling pot, which together with the coke weighs
  58lbs. 6 oz. value at 1s. per bushel                         0   1   4
  we procure 6lbs. 4 oz. of tar which we use as pith--it
  saves us                                                     0   1   0
                                                              ----------
                                                               0   2   4
  Deduct for coal                                              0   1   0
                                                              ----------
  Profit on coke and tar                                       0   1   0
                                                              ----------
  The gas yielded by the 4 pecks of coals in the pot, make
  42 brilliant lights, which burn 7 hours. To keep 42
  tallow candles which were formerly used in the manufactory
  burning for the same time, required 7lbs. which at 1s. per
  lb. cost                                                     0   7   0
  To this, add profits on coke and tar                         0   1   0
                                                              ----------
  Gained out of every bushel of coal                           0   8   0
                                                              ----------

"The gas-burners made use of in our manufactory produce jets of flame,
which in our business, where much soldering with the blow-pipe must be
done, have a decided superiority over Argand's lamps. We are not nice
concerning the quality of the gas--a great part of it is burned from the
gasometer, without allowing it to purify itself in the gasometer,
because our gasometer is not large enough to store up the whole quantity
of gas we want for use."


THEORY OF THE PRODUCTION OF GAS-LIGHT, AND DESCRIPTION OF A PORTABLE
APPARATUS FOR EXHIBITING, IN THE SMALL WAY, THE GENERAL NATURE OF THIS
SPECIES OF LIGHT.

To obtain carburetted hidrogen, or coal-gas, from common pit-coal, and
to apply it for the purposes of illumination, the coal is introduced
into large iron cylinders, called retorts, to the apertures of which
iron pipes are adapted, terminating in a vessel, or vessels, destined to
purify and collect the gas. The retorts charged with coals and made
air-tight, are placed upon the fire, the action of which extricates the
gazeous products from the coals, together with an aqueous ammoniacal
vapour, and a tenaceous bituminous fluid, or tar, &c. The liquid
substances are conveyed into proper vessels, and the gazeous products
are conducted, by means of pipes, under the gasometer, where the gas is
again washed, and remains ready for use. There are also other pipes
leading from the gasometer, which branch out into smaller ramifications,
until they terminate at the places where the lights are wanted. The
extremities of the pipes have small apertures, out of which the gas
issues, and the streams of gas being lighted at those apertures burn
with a clear and steady flame as long as the supply of gas continues.
All the pipes which come from the gasometer are furnished at their
extremities with stop-cocks to regulate the admission of the gas. The
burners are formed in various ways, either a tube ending with a simple
orifice, at which the gas issues in a stream, and if once lighted will
continue to burn with the most steady and regular light imaginable, as
long as the gas is supplied; or two concentric tubes of brass, or
sheet-iron, are placed at a distance of a small fraction of an inch from
each other, and closed at the bottom. The gas which enters between these
cylinders, when lighted, forms an Argand lamp, which is supplied by an
internal and external current of air in the usual manner. Or the two
concentric tubes are closed at the top with a ring having small
perforations, out of which the gas alone can issue, thus forming
small distinct streams of light.

[Illustration]

The gas-apparatus, plate 2, will be found very convenient for
exhibiting, in the small way, the general nature of this new art of
illumination, whilst at the same time it may serve to ascertain, at a
trifling expence, the comparative value of different kinds of coals
intended to be employed for the production of this species of light, as
well as other occasional purposes connected with the gas-light system of
illumination.

It consists of three distinct apparatus:--namely, a portable furnace,
fig. 1, plate 2, by means of which the gas is prepared--fig. 2, a
purifyer, or condenser, which separates and purifies the products
obtained from the coal, so as to render the gas fit for the purpose of
illumination--fig. 3, a gasometer, or reservoir for receiving and
preserving the purified stock of gas, and from which it may be
transferred and distributed as occasion may require. The following
statement will explain more fully the general nature of this portable
chamber apparatus:--_a_, represents a cast iron retort, such as is used
for chemical operations in the small way. This retort rests upon a
tripod of hammered iron, placed upon the bars of the grate of the
chemical furnace. Into this retort the coals are put for furnishing the
gas. It is provided with a solid iron stopper ground air-tight into the
mouth of the retort, and the stopper is secured in its place by an iron
wedge passing over it in the centre; by means of which the mouth of the
retort when charged with coal is readily made air-tight, and the stopper
may easily be removed by knocking out the iron wedge. _b._ is a metal
pipe which conveys all the distillatory products from the retort into
the purifier fig. 2. This tube is bent at right angles at the extremity
where it enters the intermediate vessel fig. 2. The purifier fig. 2, is
divided into three compartments marked _c._ _d._ _e._ The first
compartment is filled with water, and by means of it an air-tight
communication is established with the retort which furnishes the gas.
The second compartment, _d_, contains a solution of caustic pot-ash
composed of about 2 parts of caustic pot-ash and 16 of water, or a
mixture of quick-lime and water of the consistence of very thin cream.
The object of this compartment is to separate the non-inflammable gases
and other products evolved during the distillation of the coal, from the
carburetted hidrogen or coal-gas, so as to render it fit for use. The
third compartment _e_ is left empty to receive the tar and other liquid
products. Into the first compartment _c_, all the gazeous and liquid
products are delivered, as they become evolved during the distillation,
by means of the pipe _b_. The compartment _d_, of the purifier, or
alcali vessel, is furnished with a wide perpendicular pipe, which serves
to make an air-tight communication with the retort, by allowing the tube
_b_, to pass readily through it. From the chamber _c_, the liquid and
gazeous products pass to the tar-chamber, or compartment _e_, by means
of the descending pipe _f_. The tar and other condensible substances are
therefore deposited at _e_, whilst the gazeous products alone ascend
from the tar-chamber _e_, by the pipe _g_, and down again the pipe _h_,
(which is closed at the top) into the compartment _d_, of the vessel or
purifier, fig. 2. The gas being thus made to pass from the compartment
_e_, up into the pipe _g_, and down the pipe _h_, (which is closed at
the top) into the purifier _d_, is brought into contact with the liquor
in that vessel, where it is opposed to a pressure in proportion to the
perpendicular height of the column of liquid which it contains. The
funnel in the compartment _c_, is considerably higher than the purifying
apparatus, it therefore allows the liquid which it contains, when
pressed upon by the gas, to ascend into it, without overflowing the
apparatus, and to descend again as the pressure diminishes--_i_ is
another wide-mouth funnel, by means of which the chamber _d_, is filled
with the alcaline solution, or mixture of lime and water. The carbonic
acid gas and sulphuretted hidrogen, evolved during the distillation of
the coal, are thus made to combine with the alcali or lime, in the
compartment _d_, of the purifier, forming carbonate and hidro-sulphuret
of lime. The carburetted hidrogen, being left more or less pure, is
conveyed through the pipe _k_, into the gasometer, fig. 3. The
communication of the purifier, fig. 2, with the gasometer, is made by
means of the well-known water-valve _l_, placed so that the
communicating tube _k_, may be easily removed at pleasure--_m_, is a
cock for drawing off the tar, &c. _n_, a gauge-cock for ascertaining the
height of the liquid in the chamber _d_. The gasometer, fig. 3, the
object of which is to store up the gas, consists of two principal
parts--namely, a large interior vessel designed to contain the gas, and
an outer cistern or vessel, of rather greater capacity, in which the
former is suspended, designed to contain the water by which the gas is
confined. The interior vessel which contains the gas is suspended by
chains or cords hung over pullies, to which weights are attached, so as
to nearly equipoise it. _o_ is a pipe, which communicates with the
water-valve _l_, and by means of which the gas passes from the purifier,
fig. 2, into the gasometer. The upper end of this pipe is covered, in
the manner of a hood, by a cylindrical vessel _p_, open at bottom, but
partially immersed beneath the surface of the water contained in the
outer cistern of the gasometer, and perforated round near the lower edge
with a number of small holes. The gas displaces the water from this
receiver _p_, and escapes through the small holes, rising in bubbles
through the water, so as to expose a large surface to its action, that
it may be properly washed, &c. After rising through the water the gas
enters the gasometer, which is suspended to move up and down by the
chains, pullies, and balance-weights, _q_. From the centre of the
gasometer a tube, _r_, descends, which includes a pipe, _s_, fixed
perpendicular from the bottom of the cistern. The fixed pipe _r_, forms
a guide to keep the gasometer always perpendicular. _t_ is also an iron
pipe made fast in the centre of the inner vessel, and communicates with
the upright tube, _s_, in the outer vessel. This contrivance obliges the
gas to pass into the pipe _t_, whilst it also serves to keep the
gasometer steady when nearly out of the outer cistern.

When the operation commences, the gasometer is sunk down nearly to a
level with the surface of the water in the outer cistern, and is
consequently filled with water; but as the gas enters, it rises up to
receive it. It is to be noted, that the balance-weights _q_ _q_, should
not be quite so heavy as the gasometer, in order that some pressure may
be exerted, to force the gas out of the burners with a proper jet. The
gas which issues from the retort enters the purifier as stated already,
and ascends the pipe _o_, into the vessel, _p_, from which it displaces
the water, and passes out at the small holes, as before described,
rising through the water into the gasometer, and raising it up: the gas
then passes away to the burners, _u_ _u_. In this manner the process
proceeds until the whole of the volatile products of the coal in the
retort is evaporated. The use of the gasometer is, to equalize the
emission of the gas which comes from the retort more quickly at some
time than others. When this happens, the interior vessel rises up to
receive it, and when the stream from the retort diminishes, the weight
of the gasometer expels its contents. When the process is finished, the
retort is suffered to cool, and its ground stopper is then removed to
replenish it with coal. The residue found in the retort is coke. _v_ _v_
are cocks to let off any liquid that may collect in the pipe _o_ or _t_;
for if the smallest portion of liquid were to obstruct the free passage
of the gas to the burners, the consequence would be, that the lights
would not burn steadily--they would, as it is called, _dance_, or become
extinguished. _x_ is the main stop-cock which communicates with the
burners--these, of course, may be placed as convenience may require. _z_
_z_ are two projecting parts in the top of the gasometer; they are
intended to receive the hood _p_, and the upper extremity of the pipe
_t_, so as to allow the gasometer to be wholly immersed into the
cistern. The wheels or pullies of the gasometer have a groove to allow
the links of the chain to pass freely.

In this apparatus there is no provision made for the unequal pressure
which the gas suffers, accordingly as the gasometer is more or less
immersed in water. It will be observed that, in this apparatus, the
weight of the interior vessel is constantly increasing, in proportion as
it fills with gas, and rises out of the water, and consequently, if a
constant, uniform, counterpoising weight, equal only to that of the
gasometer in the first moment of its rise, be employed, the gas becomes
gradually more and more compressed by that part of the weight of the
gasometer which is not counterpoised, and if its pressure or quantity be
then estimated by the bulk which it occupies, without making allowance
for the increasing pressure, a material error must arise, and this, in
the large way, would give rise to insurmountable difficulties with
regard to the regulation of the size of the flames; which could not be
rendered uniform.

Suppose the cistern or exterior vessel full of water, and the gasometer
partly filled with gas and partly with water, it is evident that the
balance-weight may be so adjusted, as to occasion an exact equilibrium,
so that the external air shall not tend to enter into the gasometer nor
the gas to escape from it; and in this case the water will stand exactly
at the same level both within the gasometer and within the outer
cistern. On the contrary, if the balance-weights be diminished, the
gasometer will then press downwards from its own gravity, and the water
will stand lower in the gasometer than it does in the cistern; in this
case, the included air or gas will suffer a degree of compression above
that experienced by the external air, exactly proportioned to the weight
of a column of water, equal to the difference of the external and
internal surfaces of the water.

To compensate for this increasing weight of the gasometer, and render a
scale of equal graduations accurate, some have ingeniously adopted the
plan of a spiral pulley to the chain, which has the effect of gradually
avoiding the evil, but the best way of accomplishing it will be stated
hereafter.

With regard to the philosophy or the production of coal-gas, it proves
that pit-coal contains solid hidrogen, carbon, and oxigen. When the
intensity of the heat has reached a certain degree, a part of the carbon
unites with part of the oxigen and produces carbonic acid, which by
means of caloric is melted into the gazeous state and forms carbonic
acid gas; at the same time, part of the hidrogen of the coal combines
with another portion of carbon and caloric, and forms the carburetted
hidrogen gas, which varies considerably in its constitution, according
to the circumstances under which it is produced; a portion of olifiant
gas, carbonic oxid, hidrogen, and sulphuretted hidrogen, is also
produced during the process. The quantities of these products vary
according to the nature of the coal employed in the process.

Pit-coal is not the only substance which affords carburetted hydrogen;
this gazeous fluid may be obtained in a great variety of ways, and with
very considerable differences in specific gravity and proportion of
ingredients.

It is found plentifully native or ready formed on the surface of
stagnant waters, marshes, wet ditches, &c. through which, if examined
closely, large bubbles will be seen to rise in hot weather, and may be
increased at pleasure by stirring the bottom or mud with a stick.

In close still evenings if a lighted candle is held over the surface,
flashes of blue lambent flame may sometimes be perceived spreading to a
considerable distance. All that is not fabulous concerning the _ignis
fatuus_ is probably derived from this source. This species of gas is
termed for distinction the carburetted hydrogen of marshes. In the
purest form in which it can be collected it is mixed with about 20 per
cent. of azot or nitrogen.

To procure the gas for the purpose of philosophical amusement, fill a
wide-mouthed bottle with the water of the ditch, and keep it inverted
therein with a large funnel in its neck, then with a stick stir the mud
at the bottom just under the funnel, so as to cause the bubbles of air
which rise from the mud to enter into the bottle; when by thus stirring
the mud in various places, the air may be catched in the bottle.

Carburetted hidrogen gas is also given out very abundantly by all kinds
of vegetable matter when subjected to a scorching heat sufficient to
decompose them. When heated in close vessels much more gas is obtained
than when burnt in the open air. If moistened charcoal be put into an
earthen retort and heat be applied till the retort becomes ignited; gas
will be evolved, consisting partly of carbonic acid, and partly of
carburetted hidrogen. A gas of similar properties is obtained by causing
steam to pass through a tube filled with red-hot charcoal; by passing
spirit of wine, or camphor, through red-hot tubes; by distilling oils,
wood, bones, wax and tallow, or any animal or vegetable body whatever.

Indeed it would be endless to enumerate the various sources of this
gazeous fluid. A most curious variety of carburetted hidrogen gas has
been discovered by the associated Dutch chemists (VAN DIEMAN,
TROOSTWYCK, and others) which is procured from ether or alcohol, and has
the remarkable property of generating a heavy oil when in contact with
chlorine gas. Hence it has been termed oily carburetted hidrogen, or
olifiant gas--it consists of carburetted hydrogen, supersaturated with
carbon. The oil generated is heavier than water, whitish, and
semi-transparent. By keeping, it becomes yellow and limpid; its smell is
highly fragrant and penetrating--its taste somewhat sweet--it is partly
soluble in water, imparting to it, its peculiar smell. A portion of this
gas always accompanies the common carburetted hidrogen obtained from
coal, and those sorts of coal that afford the largest quantity of it are
best suited for the production of gas-light.

The nature of carburetted hidrogen obtained from coal varies
considerably according to the conditions under which it is obtained. The
first part is always much heavier than the last, though still lighter
than common air, and holds in solution a portion of oil, for on standing
for some time over water it becomes lighter, and is found to require
less oxygen for saturation than before. The oil which it held suspended,
then becomes precipitated. The average specific gravity of the first and
last gas mixed, which may be taken as an average of the whole specific
gravity is to that of common air as 2 to 3--112lb. of common cannel
coal produce at its _minimum_, from 350 to 360 cubic feet of carburetted
hidrogen gas; but the same quantity of the best Newcastle coal, that is
to say, such as coke, which, when laid on the fire readily undergoes a
kind of semi-fusion, and sends out brilliant streams of flame, produces
upon an average from 300 to 360 cubic feet of this gazeous fluid,
besides a large portion of sulphuretted hidrogen, carbonic oxid and
carbonic acid. Half a cubic foot of this carburetted hidrogen, fresh
prepared, that is to say, holding in solution or suspension, a portion
of the essential oil, which is generated during the evolution of the
gas, is equal in illuminating power to from 170 to 180 grains of tallow,
(being the quantity consumed by a candle six to the pound in one hour.)
Now, one pound avoirdupoise is equal to 7000 grains, and consequently
one pound of candles of six in the pound, burning one at a time in
succession, would last (if we take 175 grains of tallow to be consumed
in an hour) 7000/175 = 40 hours. To produce the same light we must burn
one half of a cubic foot of coal-gas per hour; therefore, one-half
multiplied by forty hours is equal to twenty cubic feet of gas in 40
hours, consequently equal to one pound of candles, six to the pound,
provided they were burnt one after another. One hundred and twelve
pounds of cannel-coal, produce, at its _minimum_, three hundred and
fifty cubic feet of gas; and are equal to three hundred and fifty,
divided by twenty, which last is equivalent to one pound of tallow,
making one hundred and twelve pounds of cannel-coal, equal to 350/20 =
17-1/2lbs. of tallow. Further, one hundred and twelve pounds of
cannel-coal, divided by seventeen and a half of tallow make six and
four-tenths of cannel-coal, equal to one pound of tallow.

With regard to Newcastle coals[17], it may be stated that one chaldron
of Wall's-End coal may be made to produce in the large way upwards of
11,000 cubic feet of crude gas; which, when properly purified,
diminishes to nearly 10,000 cubic feet.

  [17] One chaldron of Newcastle coal weighs from 2850 to upwards of
  2978lb.

The production of carburetted hydrogen, both with regard to quantity and
quality from the same kind of coal depends much upon the degree of
temperature employed in the distillatory process. If the tar and oil
produced during the evolution of the gas in its nascent state, be made
to come in contact with the sides of the red hot retorts, or if it be
made to pass through an iron cylinder or other vessel heated red hot, a
large portion becomes decomposed into carburetted hydrogen gas and
olifiant gas, and thus a much larger quantity of gas is produced than
would be obtained without such precaution from the same quantity of
coal.[18]

  [18] One pound of coal-tar produces 15 cubic feet of carburetted
  hidrogen abounding in olifiant gas.

The distillation of the coal, (if gas be the chief object) should
therefore not be carried on too rapidly. Most of the retorts used in the
large way, are calculated for containing about one hundred weight of
coal, and in general, when previously heated, produce from two and
one-half to three cubic feet of gas, in four hours for each pound of
coal they contain; but when the layer of coals in them does not exceed
four inches in depth, three and one-half to four feet of gas may be
obtained in the same time.

The retorts best calculated for large gas-light works are seven or eight
foot long (without the mouth-piece) and twelve inches in diameter,
tapering down to ten inches--if they are larger the coal which they
contain cannot be heated properly. The advantages that may be derived
from the circumstances before stated are of greater value in the
gas-light manufacture than is often imagined, and the quantity as well
as the quality of the gas is very much influenced by such circumstances.
If coal be distilled with a very low red heat scarcely observable by
daylight, the gas produced gives a feeble light--if the temperature be
increased so that the distillatory vessel is of a dull redness, the
light is more brilliant and of a better colour--if a bright or
cherry-red heat be employed the gas produced, burns with a brilliant
white flame, and if the heat be increased so far that the retort is
almost white hot, and consequently in danger of melting, the gas given
out, has little illuminating power, and burns with a clear blueish
flame;[19] or if the coal abounds in pyrites or sulphuret of iron, as is
sometimes the case with Newcastle coal, a large quantity of sulphuretted
hidrogen is likewise evolved, which although it increases the
illuminating power of the coal-gas, has the capital disadvantage, of
producing an intolerable suffocating odour, when the gas is burnt which
is particularly perceptible in low rooms illuminated with such gas.

  [19] It is chiefly a mixture of carbonic oxid, and hydrogen gas.

These observations also apply to the distillation of tar, which when
distilled either in a vaporous or nascent state, during its first
production from coal in the ordinary process, or if it be submitted to a
second distillation, mingled with a fresh portion of pit-coal, a
practice usually had recourse to when this product cannot be disposed of
more advantageously. The best depth of coal in the retort for procuring
excellent gas, and at the same time for yielding the greatest quantity
from the same weight in the shortest possible time, is about six inches.

The brightness of the coal-gas flame is rather diminished when the gas
has been long kept over water, and hence for illumination it should be
used as soon as prepared, but of course properly purified.

The quantity of gas taken up by water is affected by temperature,
because the temperature increases its elasticity; the quantity of gas
absorbed, diminishes as the temperature increases, and increases as the
temperature diminishes. 1/27 part of its own bulk of pure coal-gas is
absorbed by the water over which it is confined in the gazometer.

The chemical constitution of this gazeous fluid is best ascertained by
burning it in a vessel of oxygen gas, over lime-water in a pneumatic
reservoir, by means of a bladder and bent brass pipe. Two products are
then obtained, viz. water and carbonic acid. That water is produced, may
be shown by burning a very small stream of the gas in a long
funnel-shaped tube open at both ends. The formation of carbonic acid is
evinced, by the copious precipitation of the lime-water in the foregoing
experiment.

If carburetted hydrogen be mixed with a sufficient quantity of oxygen
gas or common air and fired by the electric spark, or by any other
method, an explosion takes place more or less violent according to the
quantity of carbonaceous matter condensed in the hydrocarbonat; and the
remaining gas consists of carbonic acid, together with any unconsumed
gas, or excess of oxygen, whilst the water condenses in drops on the
sides of the vessel. A few cubic inches of the mixed airs is as much as
can be conveniently managed at a single explosion; and when any portion
of olefiant gas is present, even this quantity will endanger very thick
glass jars. A very vivid red flame appears at the moment of the
explosion, and a great enlargement takes place in an instant, after
which the bulk is suddenly reduced to much less than the original
quantity. When the carbonic acid is absorbed by lime-water, if the
gasses have been properly proportioned, no gazeous residue is left,
except accidental impurities. Though carburetted hydrogen gas, is
sometimes naturally produced in coal-mines, and occasionally mixes with
common air, producing dreadful explosions, yet when coal-gas is mixed
with common air, it does not explode unless the gas be to the air as 1
to 10 nearly. Such are the leading chemical habitudes of this gazeous
product. The varieties of carburetted hydrogen gas all agree in being
inflammable; but they possess this property in various degrees, as is
evinced by the variable brightness of the flame which they yield when
set on fire.

"Messrs. SOBOLEWSKY and HORRER, of St. Petersburgh, have employed wood
for the purpose of producing carburetted hydrogen gas. The pyroligneous
acid obtained in this operation, when freed from the empyreumatic oil
with which it is mixed, becomes acetous acid, and is applicable to all
the uses of vinegar. A cubic cord of wood equal to 2.133 French metres
(a metre being rather more than an English yard), yields 255 Paris
pounds of charcoal, and 70 buckets of acid. The latter gives 30 pounds
of tar, after the extraction of it 50 buckets of good vinegar remain.
The same quantity of wood furnishes 50,000 cubic feet of gas, sufficient
for the supply of 4000 lamps for five hours."[20]

  [20] See Repository of Arts, Vol. XI. No. 36, p. 341.


UTILITY OF THE GAS-LIGHT ILLUMINATION, WITH REGARD TO PUBLIC AND PRIVATE
ECONOMY.

From what has been stated in the preceding pages it becomes obvious,
that a substance yielding an artificial light may be obtained from
common coal in immense quantities. The attempt to derive advantage from
so valuable a discovery is surely no idle speculation. Let us therefore
now consider to what objects of public and private utility this mode of
procuring light may be applied with effect. It is obvious that coal-gas
may be preserved in a reservoir for any length of time and that it may
be conveyed by means of tubes to any distance flowing equably and
regularly like water. Those, indeed, who have not seen the contrivance
will find it difficult to imagine with what ease it is managed. The gas
may be distributed through an infinity of ramifications of tubes with
the utmost facility. Near the termination of each of the tubes through
which it flows, it is confined by a valve or stop-cock, upon turning
which, when required to be lighted, it flows out in an equable stream
and ascends by its specific levity. There is nothing to indicate its
presence; no noise at the opening of the stop-cock or valve--no
disturbance in the transparency of the atmosphere--it instantly bursts
on the approach of a lighted taper, into a brilliant, noiseless, steady
and beautiful flame. Its purity is attested by its not blacking or
soiling in the least degree the metallic orifice from which it issues,
nor even a sheet of white paper, or polished surface brought in contact
with it. There is no escape of combustible matter unconsumed, which is
so great a nuisance in all our common lights. The products of the
combustion are water and carbonic acid gas[21]. The accurate and elegant
experiments of Dr. W. HENRY have shewn in the most satisfactory manner,
that considerably less carbonic acid is produced by the flame of
coal-gas, than by that of oil, tallow, or wax[22], which sufficiently
refutes the absurd notions that have been circulated respecting the
pernicious effects of gas-lights. But if the gas from Newcastle coal is
badly prepared, or not deprived of the portion of sulphuretted hydrogen,
which it usually contains, it then emits fiery sparks and produces a
portion of sulphureous acid by virtue of the union of the oxygen of the
air with the sulphur dissolved in the gas, the consequence of which is,
a suffocating odour, which is particularly observable in the higher
stratum of the air of apartments in which the gas is burnt. Such gas
likewise tarnishes all metallic bodies--it discolours the paintings
effected with metallic oxids, and always produces a suffocating odour
very noxious to health. It is freed from the sulphuretted hydrogen and
may be rendered fit for illumination by passing it repeatedly through
very dilute solutions of sub-acetate of lead, green sulphate of iron,
quicklime and water, or hyper-oxymuriate of lime.

  [21] The water (which passes off in imperceptible vapour) is generated
  by part of the oxygen of the air uniting with part of the hydrogen,
  which forms the great bulk of the coal-gas: and the carbonic acid gas
  is produced by the union of another portion of the oxygen uniting with
  the smaller portion of carbon, which is the other component part of
  the coal-gas.

  [22] 100 Cubic inches of carburetted hydrogen from coal, require for
  burning 220 cubic inches of oxygen and produce 100 cubic inches of
  carbonic acid--100 cubic inches of the same gas obtained from wax,
  require for burning 280 cubic inches of oxygen and produce 137 cubic
  inches of carbonic acid--100 cubic inches of the same gas procured
  from lamp-oil, require 190 cubic inches of oxygen for burning, and
  produce 124 cubic inches of carbonic acid.

  The following lines relating to the salubrity of the gas-light
  illumination are copied from Mr. Lee's evidence in the House of
  Commons, when examined on that subject.

  Question--"Is the health of your manufacturers at all affected by the
  use of gas?--Answer--Not in the least, or I would not have adopted it.
  I believe I explained to the Committee, that I used the gas-lights in
  my own house first."

  Q. "You have not seen the smallest alteration in the health of your
  workmen?--A. Not in the least, for had I seen it, it would have been a
  fatal objection to it."

  Q. "And you say the same in regard to the use of the gas-lights in
  your own family?--A. Certainly I do."

As to the brilliancy of the flame, an appeal may be made to every one
who has witnessed the gas-light illumination, whether it be not superior
to the best wax candle-light, or the light of Argand's lamps.

It may be described as a rich compact flame, burning with a white and
agreeable light. It is also perfectly steady, when the flame is limited
to a moderate size: in large masses, it is subject to that undulation
which is common to it with all flames of certain dimensions, and is
caused by the agitation of the surrounding atmosphere. The gas flame is
entirely free from smell. The coal-gas itself certainly has a
disagreeable foetid odour before it is burnt, so has the vapour of wax,
oil, and tallow, as it comes from a lamp or candle newly blown out. This
concession proves nothing against the flame of gas which is perfectly
inodorous, a white handkerchief, passed repeatedly through it and
applied to the nose, excites no odour.

Another peculiar advantage of the gas flame is, that it may be applied
in any direction we please, as there is nothing to spill and the gas is
propelled by a certain force which is always the same, it will burn
equally well in an almost horizontal as in an upright position; and we
can thus obviate two great objections to all our artificial lights, that
their least luminous end is directed downwards where the light is
generally most wanted, and that a shade is cast below by the stand or
support of the combustible matter.

The size, shape and intensity of the gas-flame may be regulated by
simply turning a stop-cock which supplies the gas to the burner. It may
at command be made to burn with an intensity sufficient to illuminate
every corner of a room, or so low and dim as barely to be perceived. It
is unnecessary to point out how valuable such lights may be in
nurseries, stables, warehouses, in the chambers of the sick, &c.

From the facility with which the gas-flame can be conveyed in any
direction, from the diversified application, size and shape which the
flame can be made to assume, there is no other kind of light so well
calculated for being made the subject of splendid illuminations.

Where lustres are required in the middle of a room, the best mode of
conducting the gas to the chandelier, is to pass the gas-pipe through
the ceiling from the room above, immediately over the lustre. This can
be easily done without injury to the apartment.

Where side-lights and chandeliers are required the tubes need never
appear in sight, but may be concealed in the wall or floor of the
house. When transparencies are wanted as decorations for halls, lobbies,
&c. more than light, recesses may be filled with different 
_media_, or paintings, and any intensity of light may be thrown on the
object.

If a number of minute holes are made in the end of a gas pipe, it forms
as many _jets de feu_, which have a very brilliant appearance; these may
sometimes be placed in the focus of a parabolic reflector. In cases
where the light is required to be thrown to a distance, other burners
are constructed upon the same principle as the Argand lamp, forming a
cylinder of flame, and admitting a current of air both to the inside and
outside.

On comparing the flame of a gas-light with the flame of a candle
whatever its size may be, it appears just as yellow and dull as the
flame of a common lamp appears when compared with that of a lamp of
Argand. The beautiful whiteness of gas-light never fails to excite the
surprize and admiration of those who behold it for the first time.

A large edifice or manufactory lighted by gas, contrasted with one of
the same kind lighted by candles or lamps, resembles a street on the
night of a general illumination, compared with the glimmering light of
its ordinary parish lamps.

The intensity of one of the parish gas-light lamps, now exhibited in the
streets of this metropolis, will bear ample testimony of this assertion;
the light of the parish gas-lamps, is to the intensity of the parish oil
lamps as 1 to 12.

One of the most obvious applications of the gas-light illumination
unquestionably consists in lighting streets, shops and houses; and let
it be observed that as this is found safe and economical, it proves all
that the most ardent friends of the gas-light system can desire. For in
contending with the common mode of lighting the streets and shops, the
new lights must beat out of the market the cheapest of all artificial
lights; and as it has succeeded in doing this it shews in the most
satisfactory point of view, the prodigious advantages of gas-lights when
compared with the materials of tallow and oil.

The original expence of laying the pipes for conveying the gas, together
with the cost of the machinery, is all that is required; the preparation
of the gas being itself a lucrative process, no doubt will pay all its
expences besides the interest of capital, and leave a surplus of profit.

Indeed the application of the coal-gas, as a substitute for tallow and
oil, to illuminate houses, shops, &c. is no longer problematical, a
considerable extent of this capital, together with numerous shops and
houses being already supplied with this species of light.[23]

  [23] The Liberty of Norton Falgate, as far as Bishopgate-street, is
  lighted with gas-light, from the Chartered Company's station at Norton
  Falgate; and gas-light pipes are laid from that station as far as the
  west end of Cheapside, and in all the streets north of that great
  thoroughfare.

  In the West end of the Town, the main pipes for supplying the streets
  and houses with light from the Gas-Light Company, extend through the
  most eligible parts; from their Establishment in Peter-street,
  Westminster, along the line from Pall Mall to Temple-bar, compleatly
  surrounding the parish of St. Martin's in the Field. Main pipes are
  also placed in the Hay-market, Coventry-street, Long-Acre, St.
  Martin's-lane; and in the principal parts of the parishes of St. James
  and St. Ann.

  In the East end of the metropolis, the gas-light _mains_ extend from
  Cornhill to St. Paul's, Wood-street, Fore-street, &c.--Consent has
  also been given to the incorporated Gas-Light Company for laying their
  pipes in the parish of St. Stephen's in the Field; St. Paul
  Covent-garden; St. Mary-le-Strand; St. Clement Danes; St. George's,
  Bloomsbury; St. Giles's in the Fields; St. Andrew's, Holborn, above
  the bars; part of the parish of St. Mary-la-bonne; besides several
  other districts, comprehending the whole of the city and suburbs of
  Westminster.

Enough therefore, has been done to prove the possibility of lighting
houses, and streets, with gas, which would have been regarded twenty
years ago as an extravagant paradox.[24]

  [24] I am informed by Mr. CLEGG, the engineer of the Chartered
  Gas-Light Company, under whose direction the new system of lighting is
  carried on, that the total length of pipe laid down, as mains, in the
  streets of London amounts already to nearly 15 miles.

  In the Eastern part of London, the same Company is engaged to lay
  their pipes in the principal parts of Whitechapel, Spitalfields, St.
  Luke's, and the adjoining neighbourhood.

  One part of the city of London, extending from Temple-bar to the West
  end of Cheapside; from Newgate-street to Holborn Bars, together with
  the intervening streets, is also provided with pipes laid down by
  another gas-light association, who have opened a new Establishment in
  Water-lane, Fleet-street, but are unconnected with the Chartered
  Company. A third company is projected in Southwark, and a fourth in
  the Eastern district of London, creating by a rivalry of interest,
  that laudable competition which always proves beneficial to the public
  at large, and which cannot fail to accelerate the progress of this new
  art of procuring light.

The Church of St. John the Evangelist in this metropolis has been
illuminated with gas-lights for upwards of two years: the lights
employed in this edifice is equal to 360 tallow candles eight to the
pound. The avenues to the House of Lords and House of Commons,
Westminster-hall, Westminster-bridge; the house and offices of the
Speaker of the House of Commons, the Mansion-house, and many other
places, deserve to be named, as having already adopted this species of
illumination.

Another advantageous application of the gas-light must be the supplying
of light-houses.

From the splendour and distinguishing forms which the gas-light flame is
capable of assuming, no light is better calculated for signal-lights
than this. By means of one single furnace as much gas might readily be
procured as would furnish a flame of sufficient intensity, during the
longest winter night, exceeding in brilliancy or intensity of light any
light-house in Britain or elsewhere.

If every light-house round this island were possessed of a gas-light
furnace, one-half part of the enormous expence which they at present
require would furnish a much more brilliant light. The cheapness of this
light and its efficacy for the purpose, would soon multiply the number
of light-houses, and thus most essentially contribute to the security of
navigation on our coast. The gas may be made to issue from tubes by long
narrow slips, and a surface of flame produced of any given dimensions,
and free from all smoke that would obscure the reflectors.

The ease with which the largest gas-light flame is instantly
extinguished by shutting the stop-cock, and the readiness with which a
long line of gas catches fire by applying a lighted taper to one
extremity, are properties that cannot fail to recommend it for the
purposes of telegraphic communications by night. Another application of
the gas unquestionably might be the lighting of barracks, arsenals,
dock-yards, and other establishments where much light is wanted in a
small place.

The annual expence of lighting the barracks of Great Britain is said to
fall little short of 50,000l. a small part of which on the new plan,
would supply them with a much purer and safer light.

The uses of the gas-lights already enumerated must of themselves,
justify us in attaching great importance to the discovery, and if
reduced to practice all over the kingdom, would employ a large capital
in a way the most advantageous and productive. But the utility of this
light will be almost indefinitely increased to the use of private
families. That such an application is practicable, in all towns of Great
Britain, is obvious, from what has been done already, and that it would
be highly economical and ornamental, there can be little doubt.

By means of gas we may have a pure and agreeable light at command in
every room of our house, just as we have the command of water, with this
singular advantage, that these lights may burn for hours within an inch
of the most combustible substance without danger, because they neither
can burn down like a candle nor emit sparks. These properties make the
gas-lights a most desirable light on board our ships of war, where
severe regulations are necessary to prevent danger from fire, which
after all are frequently evaded. The gas-light might be used in the
store-rooms, and even in the powder magazine, and the captain would
completely command the supply of light by the possession of the key
which opens and shuts the stop-cock. A small apparatus which may be
erected at a trifling expence would be sufficient for that purpose.

In shops, counting-houses, and public offices, the advantages are a
white light, nearly equal to day-light, a warmth which almost supersedes
the use of fires, a total absence of smoke, smell, and vapour, and great
economy of labour.

The heat produced by gas-lights must be observed by every one who has
had an opportunity of attending to it in the most superficial manner,
and the reason why gas-lights produce more heat than oil or candle-light
will not appear strange to our chemical readers (and who is there now
that does not know something of chemistry?) when it is considered that
the gas-light flame condenses more air than the flame of oil and tallow,
and consequently must produce more heat.

The flame of gas may be produced in so large a surface, as to be applied
to heat the most spacious apartments as well as to light them.

If the gas is made to issue by a circular rim of about twelve inches
diameter; it forms a sort of an Argand lamp on a great scale, and it is
manifest that a circumference of three feet of flame will heat the air
very rapidly, and with such uniformity that we need no longer be exposed
to the partial heating occasioned by the strong draft of a large fire. A
lamp of this description in the centre of a large room, with a very
small fire to secure a gradual renewal of the air would enable us to
enjoy the most healthful and agreeable temperature.

From trials made on this subject, I am enabled to state, that three
Argand's lamps, consuming five cubic feet of gas per hour, are
sufficient to keep a room 10 feet square at a temperature of 55 deg. Fahr.
when the air without doors has a temperature of freezing.[25]

  [25] Mr. DALTON's method of ascertaining the comparative quantity or
  effects of heat evolved during the combustion of different inflammable
  gases, and other substances capable of burning with flame, as stated
  in his System of Chemistry, vol. I. p. 76, deserves to be recommended
  to those who are more immediately interested in this subject. The
  process, which is simple, easy, and accurate, is as follows:

  Take a bladder of any size, (let us suppose for the sake of
  illustration, the bladder to hold or to be equal in capacity to 30,000
  grains of water,) and having furnished it with a stop-cock and a small
  jet pipe, fill it with the combustible gas the heating power of which
  is to be tried. Take also a tinned iron vessel with a concave bottom
  of the same capacity, pour into it as much water as will make the
  vessel and water together equal to the above stated bulk of water in
  the bladder, viz. 30,000 grains. This being done, set fire to the gas
  at the orifice of the pipe, and bring the point of the flame under the
  bottom of the tinned vessel, and suffer it to burn there, by squeezing
  the bladder till the whole of the gas is consumed. The increase of
  temperature of the water in the tinned vessel being carefully noticed
  before and after the experiment, gives very accurately the heating
  power of the given bulk of the inflammable gas.

  It was thus proved that--

  Olefiant gas raises an equal volume of water     14 deg.
  Carburetted hidrogen, or coal gas                10
  Carbonic oxid                                    4
  Hidrogen                                         5
  Spermaceti oil 10 grains burnt in a lamp raised
  30,000 grains of water                           5
  Tallow                                           5
  Wax                                              5,75
  Oil of turpentine                                3
  Spirit of wine                                   2

In all processes of the arts where a moderate heat is wanted the
gas-light flame will be found very advantageous--even on a large scale
this flame may be used with profit. It possesses advantages which cannot
be obtained from flaming fuel, where much nicety is required; because no
fuel can be managed like the flame of coal-gas. For it is well known,
that when too little air be given to flaming fuel it produces no flame,
but sooty vapour; and if too much air be admitted to make those vapours
break out into flame, the heat is often too violent. It is a fact, that
flame, when produced in great quantity, and made to burn violently, by
mixing with a proper portion of fresh air, driving it on the subject,
and throwing it into whirls and eddies, thereby mixing the air with
every part of the hot vapour, produces a very intense heat.

The great power of a gas-flame does not appear when we try small
quantities of it, and allow it to burn quietly, because the air is
not intimately brought into contact with it, but acts only on the
outside; and the quantity of burning matter in the surface of a small
flame is too minute to produce much effect.

[Illustration]

But when the flame is produced in large quantity and is freely brought
forward into contact and agitated with air, its power to heat bodies is
immensely increased. It is therefore peculiarly proper for heating large
quantities of matter to a violent degree, especially if the contact of
solid fuel with such matter is inconvenient.

As the gas-flame may be made to assume any shape and intensity, and as
there is nothing to spill, it may be exhibited under such variety of
forms and designs, as cannot fail to give rise to the most tasteful
ornamental illumination.

PLATES III. IV. and V. exhibit such designs of different kinds of
gas-lamps, chandeliers, lustres, candelabras, &c. as are already in use
in this Metropolis.

PLATE III. fig. 1, represents a _Rod Lamp_. The gas passes through the
rod _a_, to the Argand burner, which is surrounded by a cylindrical
chimney, _c_, swelling out at the lower extremity. The construction of
the Argand burner we have mentioned already, _p._ 78.

In all the gas-light burners, constructed on Argand's plan, care should
be taken that the flame be in contact with the air on all sides, and
that the current of air be directed towards the upper extremity of the
flame. This may be effected by causing a current of air to rise up
perpendicular from the bottom of the chimney glass, and to pass out
again through the contracted part, or upper extremity of the chimney;
but no other current of air should ever be permitted to come near the
gas-flame, or enter the glass chimney which covers or defends the light;
for if more air be permitted to mix with the flame than is sufficient
for the compleat combustion of the coal-gas, it necessarily diminishes
the heat, and consequently reduces the quantity of light.

Fig. 2. _A Rod Gas Lamp, with branches._ The gas passes through the
hollow rod, _a_, and part of the hollow branch, _b_, to the burner of
the lamp. The cylindrical shaped glass, _c_, exhibited in this figure,
is not so well adapted for the compleat combustion of coal-gas, as the
belly-shaped chimney, _c_, represented in fig. 1, 3, 5, 6, because the
ascending current of fresh air is not turned out of its perpendicular
course, and thrown immediately in a concentrated state, into the upper
part of the flame where the combustion of the gas is less perfect. The
exterior current of air which enters at the bottom into the lamp, rises
merely with a velocity proportioned to the length of the cylinder, and
to the rarefaction of the air in the same, but without being propelled
to the apex of the flame, as it should do, and is made to do, in the
bellied glass adapted to the lamp, fig. 1.

Fig. 3. _A Bracket Lamp._ _a_, the tube which conveys the gas to the
burner; _b_, the stop-cock of the tube.

Fig. 4. _A Pendent Rod Lamp_; in which the gas is supposed to come from
a pipe above, through the ceiling, into the pipe, _a_, to supply the
burners. The tulip-shaped chimney, _b_, of this lamp, is likewise ill
adapted for gas-light burners.

Fig. 5. _A pendent double-bracket Lamp._ The gas passing through the
perpendicular tube, _a_, into the brackets, _b_ _b_; _c_ shows the
Argand burner.

Fig. 6. _A swing Bracket Lamp._ _a_, the gas-pipe with its stop-cock;
_b_, a brass ball, communicating with the pipe, _a_; _c_, the conducting
tube, ground air-tight into the ball, _b_, and communicating with the
burner of the lamp, so as to allow it to have an horizontal motion.

Fig. 7. Shews the construction of the ball _b_, and pipe, _c_, of the
lamp, fig. 6.

Fig. 8. _A Swing Cockspur Lamp_, constructed upon the same plan as fig.
6. These two lamps are very convenient for desks in counting-houses, &c.

Fig. 9. A stop-cock with ball and socket, which, when adapted to a
gas-light pipe, allows it to have an universal motion, so that the light
may be turned in any direction.

Fig. 10. Section of the stop-cock, with ball and socket.

Fig. 11. Shows the ball and socket, fig. 9, in perspective.

[Illustration]

PLATE IV,[26] fig. 1. _A Candelabrum_; the gas pipe ascending from
the floor of the apartment, through the column _a_, and terminating in
the burner of the lamp.

  [26] The gas-lamps exhibited in this plate, are employed in the
  library, counting-house, warehouse, and offices of Mr. ACKERMAN, and,
  by whose permission, they are copied on this occasion.

Fig. 2. _A fancy pendent Cockspur Lamp._ The gas being transmitted to
the burners, _c_ _c_, by means of the pipe, _a_.

Fig. 3. _A Pedestal Argand Lamp._ _a_, the pipe and stop-cock, which
transmits to, and shuts off the gas from the burner of the lamp.

Fig. 4. _A Pedestal Cockspur Lamp._ _a_, the stop-cock and gas-pipe.

Fig. 5. _A fancy bracket Cockspur Lamp_, intended merely to show that
the coal-gas, as it passes to the burner, is perfectly devoid of colour,
and invisible. _a_ is a glass vessel furnished at its orifice with a
brass cap, _c_, and perforated ball, out of which the gas-flame
proceeds. _b_, the pipe which conveys the gas into the glass vessel,
_a_.

Fig. 6. _A Bracket Argand Lamp._ _a_ and _b_, the gas pipe communicating
with the burner.

Fig. 7 and 8. _A Horizontal Bracket Lamp._ _a_, the gas pipe, supposed
to be concealed in the ceiling. _b_, the communicating pipe, which,
together with _c_, branches out at right angles at _d_ _d_. _e_ _e_, are
the burners of the lamp.

PLATE V. fig. 1. _A Candelabrum_, into which the gas-pipe ascends from
the floor of the apartment, the lateral branches communicating with the
central tube.

Fig. 2. _An Arabesque Chandelier._ The gas enters from the ceiling of
the room into the rope-shaped pipe, _a_, from which it proceeds through
one of the arched ribs, _b_ _b_, into the horizontal hoop, or pipe, _c_.

Fig. 3. _A Roman Chandelier._ The gas enters through the inflexible
hollow chain, _a_, into the central tube, _b_, from whence the burners
are supplied by the lateral branches, _c_ _c_.

Fig. 4. _A Gothic Chandelier._ The gas is transmitted to the burners
through the rope, _a_, which includes a tube, and the communication with
the burners is established through the lateral branches.

Fig. 5. _A Pedestal Figure Lamp._ The gas is here made to pass by means
of a pipe through the body of the figure into the lattice-work
_plateau_, constructed of hollow and perforated brass tubes.

[Illustration]

Fig. 6. _A Pedestal Vase Lamp._ The gas-tube enters through one of the
claw-feet of the altar-shaped pedestal, into the glass vase, _a_, at
the bottom of which it joins the tubes communicating with the metallic
corn-ears, _b_, at the upper extremities of which it forms _jets de
feu_.

Fig. 7. _A Girandole._ The gas enters through the bracket, _a_, and is
conveyed to the burners by the descending tubes, _b_ _b_.

Fig. 8. _A Candelabrum_, having a central pipe, through which the gas is
conducted to the burner at the top.


OTHER PRODUCTS OBTAINABLE FROM COAL: NAMELY, COKE, TAR, ESSENTIAL OIL,
&c.

Having thus far considered the nature of coal-gas as a substitute for
the lights now in use, it will be necessary to attend more particularly
to some other products which are obtained during the production of this
species of light: namely, coke, tar, ammoniacal liquor, &c.

_Coke._--The substance called coke, which constitutes the skeleton of
the coal, or its carbonaceous base, is left behind in the retort, after
all the evaporable products have been expelled from the coal by
heat.--See page 85.

It is sufficiently known, that coke is a more valuable fuel than the
coal from which it is obtained.

Hence, immense quantities are prepared in the large way, but the gazeous
and other substances are lost in the process employed for carbonizing
the coal.[27] In the manufacture of coal-gas, the coke comes from the
retort, enlarged in size, and greatly diminished in weight, when
compared with the original coal. In whatever state the coal may be when
introduced into the retort, the coke is uniformly taken out in large
masses, so that the refuse coal, or dust, and sweepings of the pit,
which are now thrown away, may be employed and converted into an
excellent fuel. Coke is decidedly superior to coal for all domestic, and
more especially for culinary purposes; the heat which it throws out
being more uniform, more intense, and more durable. No flame, indeed,
accompanies it, and it seldom needs the application of the poker,--that
specific for the _ennui_ of Englishmen; but these deficiences are more
than balanced by the valuable property of emitting no sparks, of giving
more heat, and burning free from dust and smoke.

  [27] The preparation of coke is as follows:--A quantity of large coal
  is placed on the ground in a round heap, of from 12 to 15 feet in
  diameter, and about two feet in height; as many as possible of the
  large pieces are placed on their ends, to form passages for the air;
  above them are thrown the smaller pieces and coal dust, and in the
  midst of this circular heap, is left, a vacancy of a foot wide where a
  few <DW19>s are deposited to kindle it. Four or five apertures of this
  kind are formed round the ring, particularly on the side exposed to
  the wind; there is, however, seldom occasion to light it with wood,
  for other masses being generally on fire, the workmen most frequently
  use a few shovels of coal already burning, which acts more rapidly
  than wood, and soon kindles the surrounding pile; as the fire spreads,
  the mass increases in bulk, puffs up, becomes spongy and light, cakes
  into one body, and at length loses its volatile parts, and emits no
  more smoke. It then acquires an uniform red colour, inclining a little
  to white, in which state it begins to break into gaps and chinks, and
  assumes the appearance of the under part of a mushroom; at this moment
  the heap must be quickly covered with ashes, of which there is always
  a sufficient provision around the numerous fires, where the coke is
  prepared.

That coke must give out more heat during its combustion than coal, will
at once become obvious, when we consider that the quantity of matter
which, in the combustion of coal is changed from a solid to a state of
elastic fluidity, must necessarily carry off a portion of caloric,
which then becomes converted in a latent state without producing heat,
whilst the glow of the coke radiates caloric with an intensity
unimpaired by any demand of this kind.

It is thus that coke, though somewhat more difficult of ignition than
common coal, always gives out a more steady, a more lasting, and a more
intense heat.

The only inconveniences that attend the use of coke is, that, as it
consumes, it leaves much more ashes than common coal, charcoal, or wood;
and these much heavier too, which are, therefore, liable to collect in
such quantity as to obstruct the free passage of air through the fire;
and further, that when the heat is _very intense_, these ashes are
disposed to melt or vitrify into a tenacious drossy substance, which
clogs the grate, the sides of the furnace and the vessels. This last
inconvenience is only troublesome, however, when the heat required is
very great. In ordinary heats, such as are produced by kitchen or
parlour grates, the ashes do not melt, and though they are more copious
and heavy than those of charcoal or wood, they do not choke up the
fire, unless the bars of the grate be too close together.

The relative effects of heat produced by coke and coal are as follows:--

Six hundred pounds of pit-coal are capable of evaporating 10 cubic feet
of water in 20 hours, and 430lb. of coke are capable of evaporating 17
cubic feet of water in 12 hours and a half.[28]

  [28] In order to learn the relative effect of different kinds of fuel,
  with regard to their capability of producing heat, chemistry teaches
  that equal quantities of fuel alike expended, will raise the
  temperature of a given quantity of water through the same number of
  degrees; whence, by knowing the original quantity and temperature of
  water, together with the quantity of fuel expended to raise the water
  to the boiling point, the result sought may be expressed by stating
  the quantity of water at 30 degrees, which would have been raised 180
  degrees by one pound of the fuel employed; or in the form of a rule,

  Multiply the quantity of water by the number expressing the degrees
  actually raised; multiply the number of pounds of fuel expended by 180
  degrees. Divide the first product by the latter, and the quotient will
  express the water which would have been raised 180 degrees by one
  pound of the fuel. Or equal quantities of water may be compleatly
  evaporated under equal surfaces and circumstances, with the different
  kinds of fuel, the nature of which is to be examined; the quantities
  of fuel expended for that purpose give the relative effect of the
  different kinds of fuel, with regard to their power of producing
  heat.

The Earl of Dundonald has shown that, in the application for burning
lime, a quantity of coke uniformly burns a given portion of lime-stone
in one-third part of the time that the quantity of coal from which the
coke had been made could do.

This effect is to be accounted for from having previously freed the
coal, or rather its coke, from the moisture and the tar, which it sends
out during combustion, and which condenses on the middle and upper
strata of stratified limestone and coal in the lime kiln, and impedes
the whole mass of materials from coming into a rapid and compleat
ignition; because the greater the quantity of materials, and the sooner
the whole is ignited, the better and more economically the lime is
burned, both as to coals and time; the saving of which last is a
material object, especially at lime-kilns where there is in the summer
time a great demand for lime, the coke occasioning the kilns to hold a
_third more lime_ at the _same time_.

In the art of making bricks, in the smelting of metallic ores, and the
drying of malt, the advantages of coke over coal, are sufficiently
known.

The following account given by Mr. Davis,[29] shows that the advantages
that may be derived in the processes of burning lime, plaster of paris,
and bricks, by means of coke, are greater than at first sight might be
imagined.

  [29] Philosophical Magazine, Vol. 33, p. 435.

"The coke obtained in the gas process is so valuable, that it appears
inexplicable that men should not avail themselves of this mode of
procuring light, to the almost total exclusion of all other methods now
in use. As a landholder, placed among an industrious but wholly
illiterate society of men, I have had the more opportunity of trying
this species of fuel or coke, which I could not otherwise procure in
this sequestered spot, at a tolerably cheap rate, for purposes to which
it has not, as far as I know, been hitherto employed. I must tell you
that I am my own lime-burner, plaster of paris baker, and brick-maker;
and that in these processes of rural economy I have derived the greatest
benefits from this species of fuel, which I now prepare at a cheap rate,
although I waste almost the whole of the light of the coal gas
intentionally. The coal which I employed formerly for the burning of
limestone into lime, is a very inferior kind of small coal, called here
Welsh culm. The kiln for burning the limestone into lime is a cup-shaped
concavity, surrounded with solid brick-work, open at the top, and
terminating below by an iron grate. It has a stone door that may be
opened and closed for charging and emptying the furnace when required.
This furnace I formerly charged with alternate strata or layers of small
coal and limestone, the latter being broken previously into pieces not
larger than a man's fist, until the kiln was completely filled. The
stone is thus slowly decomposed; the upper part of the charge descends,
and when it has arrived at the bottom of the furnace new strata are
super-imposed, so as to keep the furnace continually full during a
period of 50 hours. The quantity of lime I procured with small coal
formerly amounted to 85 bushels. The strata of coal necessary for the
production of this quantity of lime require to be four inches thick, and
the time necessary for calcination was, as stated already, 50 hours.

"On applying coke instead of coal, the produce of lime may be increased
to nearly 30 per cent. from the same furnace, and the time required to
effect the calcination of this quantity of lime-stone is reduced to 39
hours: it also requires _less attendance_ and _less labour_, and the
whole saving, thus accomplished, amounts to more than 50 _per cent. on
the lime-kiln_.

"I have lately also employed coke for the burning of bricks. My bricks
are burnt in clamps, made of bricks themselves. The place for the fuel,
or fire-place, is perpendicular, about three feet high. The flues are
formed by gathering or arching the bricks over, so as to leave a space
between each of a brick's breadth; and as the whole of the coal, if this
fuel be employed, must, on account of the construction of the pile, be
put in at once, the charge of the bricks is not, and never can be, burnt
properly throughout; and the interference of the legislature, with
regard to the measurement of the clamp, is a sufficient inducement for
the manufacturer to allow no more space for coal than he can possibly
spare.

"If coke be applied instead of coal, the arches, or empty spaces in the
clamp or pile, as well as the strata of the fuel, may be considerably
smaller: the heat produced in this case is more uniform and more
intense, and a saving of 30 per cent. at least is gained.

"In the baking my own plaster-stone I also employ coke. The calcination
of the stone for manure I perform in a common reverberatory furnace, and
the men who conduct the process (who are otherwise averse to every thing
new) are much pleased with the steadiness of the fire, and little
attendance which the process requires, when coke is used instead of
coal.

"These are the few facts I wish to state, with regard to the useful
application of this species of fuel, which, no doubt, hereafter will
become an object of economy of incalculable advantage to individuals, if
its nature be better understood than it is at present."

The quantity of coke obtainable from a given quantity of coal varies
according to the nature of the coal employed. One chaldron of Newcastle
coal produced, upon an average, in the gas-light manufacture, from one
chaldron and a quarter to one chaldron and a half of well formed coke.
If the carbonization of the coal has been carried to its utmost point,
the coke produced, has a brilliant silvery lustre. Such coke is
excellent for metallurgical operations, because it stands the powerful
blast of the bellows, but for culinary and other purposes of domestic
economy, the carbonization should not be carried so far, because, the
coke then produced, kindles more readily and makes a more cheerful fire.

_Coal-tar_, _Oil_, and _Pitch_.--Another, valuable product obtainable
from pit-coal, is coal-tar.[30] This substance is deposited, in the
purification of the coal-gas, in a separate vessel destined to receive
it.

  [30] In the year 1665, Becher, a German chemist, brought to England
  his discovery for extracting tar from coal, this distillation he
  performed in close vessels. It is not mentioned in the records of the
  time, whether Becher obtained, or rather collected, any other articles
  than the tar.

The coal-tar is so called from its resembling common tar in its
appearance, and most of its qualities.

Several works have been, at different times, erected both in England and
on the continent, to procure from coal a substitute for tar; but they
turned out unprofitable speculations. In 1781, the Earl of Dundonald
invented a mode of distilling coal in the large way, which enabled him
not only to form coke, but, at the same time, to save and collect the
tar. Even this process however, for which a patent was taken out, has
gained very little ground. Its object was still too limited; for though
some of the ingredients of coal were procured, they were procured at an
expense that nearly balanced the profits; and no attention whatever was
paid to the coal gas, which constitutes the most important part of coal.

Coal-tar may be used with advantage for painting and securing wood that
is exposed to the action of air or water. The wood being warmed, the tar
is applied cold, and penetrating into the pores, gives the timber an
uncommon degree of hardness and durability.

One chaldron of Newcastle coal produces in the gas-light manufacture
from 150 to 180lb of tar, according to the circumstances under which it
is produced. See page 94.

The tar obtained from Newcastle coal-tar is specifically heavier than
that produced from cannel-coal; hence it sinks in water, whereas the
latter swims on the surface of that fluid.

To render the tar fit for use, it requires to be evaporated to give it a
sufficient consistence. If this process be performed in close vessels,
a portion of an essential oil is obtained, which is known to colourmen
by the name of oil of tar. To obtain this oil, a common still is filled
with the coal-tar, and, being properly luted, the fire is kindled and
kept up very moderate, for the tar is very apt to boil up in the early
part of the process. The first product that distils over is principally
a brown ammoniacal fluid, mixed however with a good deal of oil. As the
process advances, and the heat is increased, the quantity of ammoniacal
liquor lessens, and that of oil increases, and towards the end of the
distillation the product is chiefly oil.

The oil and ammoniacal water which distil over do not mix, so that they
may be easily separated by decantation. The oil is a yellowish inferior
kind of oil of turpentine, which is very useful in painting ships, for
making varnishes, and other coarse out-door work.

Two hundred pounds of tar produce, upon an average, fifty-three pounds
of essential oil.

If the coal-tar is wanted to be converted into pitch, without obtaining
the oil which it is capable of furnishing, the evaporation of it may be
performed in a common boiler; but as it is extremely liable to boil
over, the greatest precaution is necessary in conducting the
evaporation. A boiler constructed on the following plan is very
convenient for the conversion of coal-tar into pitch. The contrivance
consists in adding a spout, or rim, to the common boiler, into which the
tar spreads itself as it rises, and by this means becomes cooled, and
the boiling over is checked.

[Illustration: _Kettle for boiling Tar._]

1000lb. of coal-tar produce, upon an average, from 460 to 480lb. of
pitch. A subsequent fusion, with a gentle heat, converts the coal-pitch
into a substance possessing all the characters of _asphaltum_.

_Ammoniacal Fluid._--The properties of the ammoniacal liquor, which
accompanies the tar, and which is deposited in the tar-cistern, has not
yet been fully investigated. It is employed already in the manufacture
of muriate of ammonia (sal ammoniac). One chaldron of coal affords from
220 to 240lb. of this ammoniacal fluid, which is composed chiefly of
sulphate, and carbonate of ammonia.--Such are the products obtainable
from coal.

However certain the practicability of extending the new lights to the
dwelling houses of every town and village is, it cannot be expected that
such an event should take place speedily and generally. To eradicate
prejudice, and to alter established habits, is a work which nothing but
time can effect; because prejudice is the effect of habit, and can
seldom be eradicated from the minds of such individuals as consider the
ready occurrence of a proposition as a test of its truth. To establish a
new philosophical theory has, in every instance, required time
sufficient to educate an entire generation of men. The rejection of the
Aristotelian philosophy--the adoption of experimental research--the
substitution of the doctrine of gravitation instead of that of vortices,
and the rejection of phlogiston by modern chemists, are sufficiently
illustrative of this assertion. New arts, and new practices, are still
more difficult to be introduced. The new art of bleaching need merely be
mentioned to prove this assertion. The new grammar--the new rudiments of
science--the new stile--or the new instrument, however superior to the
old in simplicity, facility, and truth, must be less valuable to the
ordinary teacher or artisan, whose memory is familiarized with the
precepts of the latter, and whose only ambition is to earn his
subsistence with the least possible exertion.

The slowness with which improvements of every kind, make their way into
common use, and especially such discoveries as are most calculated to be
of an extended or general utility is very remarkable, and forms a
striking contrast to the extreme avidity with which those unmeaning
changes are adopted, which folly and caprice are continually sending
forth into the world under the auspices of _fashion_.

On the first view of the subject it appears very extraordinary, that any
person should neglect, or refuse to avail himself of a proposed
invention, or improvement, which is evidently calculated to economise
his labour, and to encrease his comforts; but when we reflect on the
power of habit, and consider how difficult it is for a person even to
perceive the disadvantages or imperfections of former modes to which he
has been accustomed from his early youth, our surprize will be
diminished, or vanish altogether.

Many other circumstances, besides prejudice, are unfavourable to the
introduction of new and useful discoveries. Among these jealousy,
malice, envy, and revenge, have too often their share in obstructing the
progress of real improvement, and in preventing the adoption of plans
evidently calculated to promote the public good.

A plan like the present, which proposes not only to trench upon domestic
habits, but to give an entire new direction to a portion of the skill
and capital of the country, must necessarily encounter the most
strenuous opposition. It is thus that some individuals have mustered all
their strength against the introduction of this new art. An endeavour
has been made to move the public opinion by dismal forebodings of the
Greenland trade, and the subsequent loss of a nursery of British seamen.
This objection is nothing more than the common clamour that is always
set up against every new means of abridging labour, to which had the
public listened, an interdict would have been laid upon the spinning and
threshing machines, the steam engine, and a thousand other improvements
in machinery.

Indeed such clamour scarcely ever fails to be made when the extension of
machinery and the abridgement of labour or the application of inanimate
powers are considered. On such occasions, it is stated by certain humane
but mistaken objectors, that the scheme of mechanical and chemical
improvement is pointed against the human species--that it tends to drive
them out of the system of beneficial employment--that the introduction
of machinery is injurious to the labouring class of society, by
abridging their work. Two creatures offer themselves for employment and
support--a man and a horse. I must invariably prefer the latter, and
leave the former to starve. Two other beings--a horse and a
steam-engine, are candidates for my favour. My preference to the latter
tends to exterminate the species of the former. In both cases it is
stated, that the number of intelligent creatures capable of the
enjoyment of happiness must be diminished for want of support; and that,
on the whole, the sum of the proposed improvement is not only a less
proportion of good to society, but a positive accession of misery to the
unemployed poor.

On this wide and extended argument, which can in fact be maintained
against all improvements whatever in no other way than by insisting that
the savage state of man, with all its wants, its ignorance, its
ferocity, and its privations, is preferable to the social intercourse of
effort and division of labour we are habituated to prefer, it may be
sufficient to observe that it includes matter not only for reasoning and
induction, but also for experiment. By reference to the matter of fact,
though it must be allowed that new improvements, which change the habits
of the poor, must at first expose them to a temporary inconvenience and
distress, against which, in fairness, it is the duty of society to
defend them; yet the invariable result of such improvements is always to
better the condition of mankind. A temporary inconvenience to
individuals must often be incurred for the sake of general national
benefit.

It is to manufactories carried on by machinery and to the abridgment of
labour, that this country is indebted for her riches, her independence
and pre-eminent station among the nations of the world.

But let us return to the subject.--The progress of the new mode of
lighting with coal-gas can never wholly supersede the use of candles and
moveable lights. The objection with regard to the Greenland trade is
equally futile. This traffic, might with more propriety be called a
drain, than a nursery, of the naval force. The nature of the Greenland
service requires that the crew should consist chiefly of able-bodied
sailors; and being protected men, not subject to the impress law, they
are thus rendered useless for national defence. The nursery of British
seamen is the coasting trade; and if the gas-light illumination be put
in practice to a large extent, it will increase that trade as much as it
will diminish the Greenland fishery.

Even on the extreme supposition that it would annihilate the Greenland
fisheries altogether, we should have no reason to regret the event. The
soundest principles of political economy must condemn the practice of
fitting out vessels to navigate the polar seas for oil, if we can
extract a superior material for procuring light at a cheaper rate from
the produce of our own soil.

Indeed the fisheries will find ample encouragement, and the consequence
of lighting our streets with gas can prove injurious only to our
continental friends, one of whose staple commodities, tallow, we shall
then have less occasion to purchase.

There will be less waste indeed, but a greater consumption of coal. The
lower classes of the community are at present very scantily supplied
with firing; and nothing but a reduction of price is necessary to
increase to a very large amount the whole average quantity of fuel
consumed in the country. The lightness of the coke produced in the
gas-light manufacture diminishing the expence of land carriage, will
facilitate its general diffusion--the comforts of the poor will be
materially augmented, and a number of useful operations in agriculture
and the arts be carried on, which are now checked and impeded by the
price of fuel.

If any additional want were wanted for the coke it will readily be
found in the continental market; coke being much better suited than coal
to the habits of most European nations.

The gas-light illumination cannot tend to diminish the coal-trade; on
the contrary it will prove beneficial to it; it will contribute to lower
the price of the superior kinds of coal, and keep a level which cannot
be shaken under any circumstances; it will contribute to prevent
combinations which do certainly operate to the prejudice of the public,
and do sometimes put this great town at the mercy of particular
proprietors in the north, who deal out coal in the way they please. The
competition thus produced, it is impossible not to consider as an
advantage, which would prevent in future such combinations, and put
those in London out of the reach of them.

It is worthy observation, that the annual importation of coal into this
Metropolis, is above one million and eighty-eight thousand
chaldrons.[31]

  [31] To give an idea how long there is a probability of Great Britain
  being applied with coal from the rivers Tyne and Wear only, it must be
  observed,

  _1st_. That the Seams of coal which are now worked at Newcastle and
  Sunderland, are equal to a seam or bed of 15 miles by 20 miles.

  _2dly_. That this seam, on an average, is at least four feet and a
  half thick.

  _3dly_, That 1-6th part of the above extent is sufficient for pillars
  to support the roofs of the mines, &c.

  And, _4thly_, It appears, by experiments, that a cubic yard of coal
  weighs 1 ton, or 20 cwt.

                                                        London Chaldrons

  The total consumption of coal from the rivers Tyne
  and Wear known from the register to be                  2,300,000

  The number of tons in the above quantity taking the
  London chaldron at 27 cwt. is                           3,100,000

  Now a ton weight of coal is estimated to occupy in
  the earth the space of one cubic yard.

  The number of cubic yards in the square mile is         3,097,600

  The beds or seams of coal are, on an average, 4
  feet and a half in thickness, which increases the
  above number of cubic yards in the square mile by
  half the number of square yards to                      1,548,800

  And hence the square mile of the beds or seams of
  coal we are describing contains, of cubic yards
  and tons of coal                                        4,645,000

  A deduction of 1-6th for pillars to support the
  mine, &c.                                                 800,000

  The number of tons per square mile                      5,445,000

  We have already mentioned the length and breadth of the seams of coal
  to be equal to 20 miles by 15, making an area of 300 square miles, and
  consequently a source of consumption for 375 years.

It may be objected to the universality of our conclusion, that the price
of coals, differing very much in different places, will occasion a
variation in the expence of the new mode of illumination. But there are
two reasons why this should have less place, because we find, in Mr.
Murdoch's statement, page 69, that of 600l. the estimated yearly expence
of lighting the cotton mill, 550l. consist of interest of capital, and
tear and wear of apparatus, leaving the cost of coal only 50l. a sum so
trifling, when we reflect that it replaces 2000l. worth of candles, that
the price of coal, even where it is highest, can but slightly affect the
general profits.[32]

  [32] See, also, Mr. Ackermann's statement, page 71.

_2dly_, The coal, by yielding the gas and other products,--namely, tar,
pitch, ammoniacal liquor, &c. of which we have treated already, is
converted into a substance, increased in bulk, and in the power of
producing heat, namely, coke; and as a manufactory generally requires
heating as well as lighting, there will be a gain both ways. The
manufacturer, by distilling his coal, instead of burning it as it comes
from the pit, will save his candles and improve his fuel. One effort at
the outset, in erecting a proper apparatus, will reduce his annual
disbursement, for these two articles of prime necessity, much in the
same manner, (though in a far greater degree) as the farmer gains by
building a thrashing machine and laying aside the use of the flail.

The principal expence in the pursuit of this branch of civil and
domestic economy is therefore the dead capital employed in erecting the
machinery destined for preparing and conveying the gas; the floating or
live capital is comparatively small. At the same time, were we to offer
an advice to the public on this subject, it would be, that no private
individual resident in London should attempt to light his premises for
the sake of economy with coal-gas by means of his own apparatus, whose
annual expence for light does not exceed 60l. because the expence of
erecting and attending a small apparatus is almost as great as one
constructed on a larger scale would be. For if the quantity of gas
wanted is not sufficient to keep the retorts continually in a red-hot or
working state, the cost of the gas will be considerably enhanced;
because either the empty retorts must be continued red-hot, or the fire
must be suffered to go out; and the retorts, when cold, cannot be
brought to a working state, that is to say, be made red hot again, but
at a considerable expence of fuel, which must be wasted to no purpose.
Whereas, if the retorts are constantly kept red hot and in action, one
half of the coal necessary to produce a given quantity of gas will then
be saved. But when a street, or a small neighbourhood is wanted to be
lighted, and the retorts can always be kept in a working state, that is
to say, red hot, the operation may be commenced with safety; because the
sum required for erecting the apparatus, and the labour attending it,
together with the interest of money sunk, will then soon be liquidated
by the light which it will afford.

Individuals, therefore, may engage in the distillation of coal, and
trade with advantage in the articles produced by that process, and the
lighting of cities may be accomplished without the aid of incorporated
bodies; and parishes may be lighted by almost as many individuals as
there are streets in a parish.

From experiments, made by Mr. CLEGG, on the effects produced by a number
of gas-lights, of a certain intensity, there is reason to believe that
the streets of small towns might be illuminated at a cheaper rate, by
means of a tower, or pagoda, furnished with gas-lamps, than can be done
in the ordinary way by street lamps: the gas being conducted to the top
of the building from the apparatus below, and the light directed down
again, upon the objects to be illuminated, by means of reflectors placed
at a certain angle. By this contrivance, all the main pipes which convey
the gas through the streets, as well as those collateral ones that
branch out from them to the street lamps, would be saved, and thus
compensate for the expense of the tower.

The most beneficial application of gas-lights unquestionably is in all
those situations where a great quantity of light is wanted in a small
place: and where light is required to be most diffused, the advantages
of this mode of illumination are the least.--Hence, as already stated,
the lighting of the parish, or street-lamps only, without lighting shops
or houses, can never be accomplished with economy.

We have noticed before the reason why the price of coals can have little
effect upon the gas-light; because the very refuse, or small coals,
called slack, which pass through the screen at the pit's mouth, and
which cannot be brought into the market--nay, even the sweepings of the
pit, which are thrown away, may be employed for the production of
coal-gas. It makes no difference in what form the coal is used, and this
circumstance may contribute to enable the coal-merchant to furnish coals
in larger masses, and as they come from the mine, instead of increasing
the bulk by breaking them into a smaller size,[33] which is a practice
commonly adhered to. This unquestionably reduces the value of coals;
because the quantity of radiant heat generated in the combustion of a
given quantity of any kind of fuel depends much upon the management of
the fire, or upon the manner in which the fuel is consumed. When the
fire burns bright, much radiant heat will be sent off from it; but when
it is smothered up, very little will be generated: most of the heat
produced will then be expended in giving elasticity to a thick dense
vapour, or smoke, which is seen rising from the fire; and the combustion
being very incomplete, the carburetted hidrogen gas of the coal being
driven up the chimney without being inflamed, the fuel is wasted to
little purpose.

  [33] It is not generally apprehended, how very wasteful the use of
  small coals is in the ordinary open fire-grates. Necessity makes us
  use the poker very much, particularly, when the coals are small; and
  habit prevails even when they are large. By the constant stirring of
  the fire almost the whole of the small coal passes through the bars;
  and consequently a great deal goes to the dust-hole without being
  burnt at all. To prove this, we need only take a shovel full of ashes
  and put them into a pail, and then pouring water over them, which
  being gently run off, will carry away nearly all the light and burnt
  parts: and leave an astonishing quantity of bright unburnt coal, which
  has escaped from the fire-place, in consequence of being small.

  When the grate of the fire-place is large, and the small coals are
  thrown behind; or when we can have patience enough to bear the cold
  for an hour or two, or contrive to have the fire lighted a long time
  before we want it, the small coal may be of some use, but the fire
  made with it is never strong, nor so bright; and does not burn so long
  as a fire made with large or round coals: it often requires the help
  of the poker, and produces a great quantity of breeze.

  The loss in the use of small coals is more considerable to the poor,
  who cannot keep large fires. When they want their breakfast or dinner,
  the time they can spare is limited; and to have their water sooner
  boiling, or their meals quicker ready; they must make use of the
  poker, and lose a great deal of coal. This fact is so evident, that
  any body who wishes to make the experiment before recommended, will
  find that much more bright coal goes to the dust-hole of the poor man,
  than to the dust-hole of a rich family, where, the fire-place being
  large, the small coal has more chance of burning.

  The loss is still greater to the poor, in consequence of the inferior
  sorts of coal which are sold to them. If it is the light sort, it
  burns too quick, and they consume double the quantity; if the strong
  sort, it burns too slow, and is nearly as wasteful; for a great
  quantity of it then goes to the dust-hole without having been lighted
  at all.

  An incorrect opinion is often entertained, that the real quantity of
  coal contained in a sack is lessened by separating or screening the
  small from the round coals; but we must recollect, that any compact
  body occupies less space than is required to contain the same matter,
  reduced to smaller irregular pieces, or to powder.--Now the screening
  only takes away the finest dusty part of the coals, and admits more
  small pieces of round coals to be filled into the sack.

Nothing can be more perfectly devoid of common sense, and wasteful and
slovenly at the same time, than the manner in which chimney fires, where
coals are burnt, are commonly managed by servants. They throw on a load
of (perhaps all small) coals at once, through which the flame is hours
in making its way; and frequently it is not without much care and
trouble that the fire is prevented from going quite out. During this
time no heat is communicated to the room; and, what is still worse, the
throat of the chimney being occupied merely by a heavy dense vapour, not
possessed of any heating power, and, consequently, not having much
elasticity, the warm air of the room finds less difficulty in forcing
its way up the chimney and escaping, than when the fire burns bright,
and the coal-gas is ignited. And it happens not unfrequently, especially
in chimnies and fire-places ill-constructed, that this current of warm
air from the room which presses into the chimney, crossing upon the
current of heavy smoke and aqueous vapour which escapes slowly from the
fire, obstructs it in its ascent, and beats it back into the room. Hence
it is that chimnies so often smoke when too large a quantity of fresh
coals is put upon the fire. So many coals should never be put on the
fire at once as to prevent the free passage of the flame between them,
or to prevent them becoming quickly heated, so as to give out the
carburetted hidrogen gas which they are capable of furnishing, and to
cause it to be inflamed, In short, a fire should never be smothered: and
when attention is paid to the quantity of coals put on, there is little
use for the poker; and this circumstance will contribute much to
cleanliness, and the preservation of furniture.

The author of a paper in the Plain Dealer asserts, that, of the various
perversions of abilities, there is none that makes a human being more
ridiculous, than that of attempting to stir a fire without judgment; to
prevent which he lays down the following rules:--1. Stirring of a fire
is of use, because it makes a hollow where, the air being rarefied by
the adjacent heat, the surrounding air rushes into this hollow, and
gives life and support to the fire, and carries the flame with it. 2.
Never stir a fire when fresh coals are laid on, particularly when they
are very small, because they immediately fall into the hollow place, and
therefore ruin the fire. 3. Always keep the bottom bars clear. 4. Never
begin to stir the fire at the top, unless when the bottom is quite
clear, and the top only wants breaking.

There is one subject more on which it is necessary to speak.--In the
present instance, the public has been alarmed by representations that
the general adoption of gas-lights would expose us to innumerable
accidents, from the inflammable nature of the gas, and the explosion of
the apparatus in which it is prepared, or the bursting of the pipes by
which it is conveyed. But there is no ground for such fears.

Those who are familiar with the subject will readily allow, that there
is no more risk in the action of a gas-light machinery, properly
constructed, than there is in the action of a steam-engine, built on
just principles.

The manufacture of the coal-gas requires nothing more than what the most
ignorant person, with a common degree of care and attention, is
competent to perform. The heating of the gas-furnace, the charging of
the retorts with coal, the closing them up air-tight, the keeping them
red-hot, and discharging them again, are the only operations required in
this art; and these, surely, demand no more skill than a few practical
lessons can teach to the meanest capacity. The workman is not called
upon to exercise his own judgment, because, when the fire is properly
managed, the evolution of the gas goes on spontaneously, and without
further care, till all the gas is extricated from the coal.

No part of the machinery is liable to be out of order,--there are no
cocks to be turned, no valves to be regulated; nor can the operator
derange the apparatus but by the most violent efforts. And when the
stock of gas is prepared, we may depend on its lighting power as much
as we depend on the light to be obtained from a certain number of
candles or oil-lamps.

The diversified experiments which have been made by different
individuals, unconnected with each other, have sufficiently established
the perfect safety of the new lights; and numerous manufactories might
be named in which the gas-lights have now been in use for upwards of
seven years, where nothing like an accident has occurred, though the
apparatus in all of them is entrusted to the most ignorant man.

It would be easy to state the causes which have given rise to some of
those accidents that have spread alarm amongst the public; but of this
it is not my business to speak at length. It is sufficient, on the
present occasion, to state, that those melancholy occurrences which have
happened at some gas-light establishments which I have had an
opportunity of examining, were totally occasioned by egregious failures
committed in the construction of the machinery. Thus, an explosion very
lately took place in a manufactory lighted with coal-gas, in consequence
of a large quantity of gas escaping into a building, where it mingled
with common air, and was set on fire by the approach of a lighted
candle. That such an accident could happen, is an evident proof that the
machinery was erected by a bungler, unacquainted with the most essential
principles of this art; because such an accident might have been
effectually prevented, by adapting a waste pipe to the gasometer and
gasometer house. By this means, if more gas had been prepared than the
gasometer would contain, the superfluous quantity could never have
accumulated, but would have been transported out of the building into
the open air, in as an effectual manner as the waste-pipe of a water
cistern conveys away the superfluous quantity of water, when the cistern
is full. Such an expedient did not form part of the machinery.

Other instances might be named, where explosions have been occasioned
through egregious mistakes having been committed in the erection of the
gas-light machinery, were this a subject on which I meant to treat.

That the coal-gas, when mixed with a certain portion of common air, in
close vessels, may be inflamed by the contact of a lighted body, as has
been stated, page 98, is a fact sufficiently known. But the means of
preventing such an occurrence in the common application of gas-lights,
are so simple, easy, and effectual, that it would be ridiculous to dread
danger where there is nothing to be apprehended. In speaking thus of the
safety of the gas-light illumination, I do not mean to deny that no
possible circumstances may occur where the coal-gas may be the cause of
accident. It is certain that the gas, when suffered to accumulate in
large quantities in close and confined places, where there is no current
of air, such as in cellars, vaults, &c. and where it can mix with common
air, and remain undisturbed, that it may be liable to take fire when
approached by a lighted body; but I do not see how it is probable that
such an accumulation of gas should take place in the apartments of
dwelling houses. The constant current of air which passes continually
through the rooms, is sufficient to prevent the possibility of such an
accumulation ever to take place. And with regard to the bursting of the
pipes which convey the gas, no accident can possibly happen from that
quarter; because the gas which passes through the whole range of pipes
sustains a pressure equal to the perpendicular weight of about one inch
of water only, and such a weight of course is insufficient to burst iron
pipes. Nor could the town when illuminated by gas-lights, be thrown
suddenly into darkness, as has been asserted might happen by the
fracture of a main pipe, supposing such an event should take place;
because the lateral branches, which supply the street-lamps and houses,
are supplied by more than one main; and the consequence of a fracture
would be only an extinction of the few lamps in the immediate vicinity
of the broken pipe, because the rest of the pipes, situated beyond the
fracture, would continue to be supplied with gas from the other mains,
as will become obvious from the sketch exhibited in the next page.

[Illustration: Main pipe, leading from the Gas-light station or
apparatus, situated in Brick Lane, near Old St.[34]

Main pipe, leading from the gaslight apparatus, or station, at Norton
Falgate.[35]

Main pipe, leading from the gaslight apparatus, or station, in
Westminster.[36]]

  [34] _The gasometer at this place is equal in capacity to 22000 cubic
  feet._

  [35] _The capacity of the gasometer here is equal to 15928 cubic
  feet._

  [36] _At this station the gasometer is equal in capacity to 14808
  cubic feet._

The black lines represent the gas-light mains, or largest pipes, from
which the smaller pipes branch off: they are connected with each other
at the places marked A B C; and the dotted lines represent the smaller
mains, or collateral branches before-mentioned. The main pipes are all
furnished with valves, or cocks, placed at about 100 feet distant from
each other. Now let us suppose that a main pipe, in any part of the
street marked in the sketch, _Pall Mall_, should break, it is evident,
on mere inspection, that the gas which is passing through the main in
the _Strand_, and which is also connected with the main in the
_Haymarket_, _Piccadilly_, and _Coventry Street_, would continue to
supply the broken pipe, and the valve nearest to the fracture being
shut, would prevent the loss of any considerable quantity of gas, and
the few lamps situated between the two valves and the fracture would
therefore only become extinguished.

Further, let us suppose a main pipe should break in _Piccadilly_; in
that case, the valve being shut on each side of the fracture, the gas
would be supplied from the mains in the _Haymarket_ and _St. James's
Street_. And the same effect would be produced in any part of the town,
supplied with gas-pipes. Besides all this, in the statement thus far
given, we have assumed that all the gas-light mains are supplied with
gas from one manufacturing station only, but which in reality is not the
case. The range of pipes that convey the gas is connected with three
gas-light establishments, situated at different parts of the town; and
the gas which is supplied from these stations is connected with the
whole system of pipes in the streets.[37] If, therefore, one of the
manufactories should be annihilated, it would make no difference,
because the lights would be amply supplied from the other two
manufacturing stations. Hence it is obvious, that the fracture of any of
the gas-light mains, or even the total destruction of one or more of the
manufactories themselves, would be attended with no serious consequence;
and as the system of lighting with gas becomes more extended, the
manufactories, or stations for supplying it, will also be multiplied, to
give effect and security to the whole.

  [37] As shown in the sketch.

In fact, no danger can arise from the application of gas-lights in any
way, but what is common to candle-light, and lamps of all kinds, and is
the fault of none of them. Even in this case the gas-lights are less
hazardous. There is no risk of those accidents which often happen from
the guttering or burning down of candles, or from carelessly snuffing
them. The gas-light lamps and burners must necessarily be fixed to one
place, and therefore cannot fall, or otherwise become deranged, without
being immediately extinguished. Besides, the gas-light flames emit no
sparks, nor are any embers detached from them. As a proof of the
comparative safety of the gas-lights, it need only be stated, that the
Fire-offices engage themselves to insure cotton-mills, and other public
works, at a less premium, where gas-lights are used, than in the case of
any other lights.[38] The excessive expence of insurance arising from
the numerous candles employed in most of the first rate manufactories,
and the combustible nature of the structure of the buildings; the great
difficulty of retrieving the injury resulting to a well-organised
business, from the accidental destruction of the machinery, are objects
alone sufficient to furnish the strongest economical, as well as
political recommendations, for the adoption of the new lights in all
manufactories where work is done by candle-light.

  [38] Since the preceding pages have been printed, I have seen a
  _self-extinguishing gas-lamp_, invented by Mr. CLEGG. This lamp is so
  constructed, that the gas cannot flow to the burner, when the flame
  becomes extinguished. If, therefore, the lamp should be blown out, and
  the stop-cock which supplies the gas be left open, the extinction of
  the flame will effectually shut the valve. The action of this lamp
  depends upon the expansibility of a metallic rod, heated by the flame
  of the lamp, and thus keeping open the valve, whereas, when the lamp
  is extinguished, and the rod becomes cold, it contracts to its natural
  dimensions, and, by that means, effectually closes the valve. The same
  engineer has invented a machine, which both measures and registers, in
  the absence of the observer, the quantity of gas delivered by any pipe
  communicating with a gas-light main. The machine occupies a space of
  about two feet by one foot, and, if put up in a room, house, or other
  place, where gas is burnt, will, at any time, by mere inspection, give
  an account of the quantity of gas consumed in that place during any
  given time. On the present occasion, it would not become me to say
  more on these subjects, which, no doubt, Mr. CLEGG will make known to
  the public; I shall only remark, that these contrivances do signal
  honour to the talents and abilities of the inventor; and that they
  will render the greatest services to those who are engaged in the
  gas-light illumination.

After considering the facts so far detailed, many other advantages,
connected with the gas-light illumination, will naturally suggest
themselves to the reader. I have endeavoured merely to point out the
leading characters of the new lights, as they are at present. Ingenious
men may speculate from what has been done to what remains to be
effected, which, no doubt, will embrace objects of the greatest utility
and most extended national importance. The public attention is awakened
to the new properties of coal, and will not rest till they are
extensively applied to economical purposes. The consequence will be, a
considerable defalcation in the revenue. For, in proportion as the
gas-lights are more or less generally adopted in all towns of the
country, the consumption of oil and tallow will be diminished, and the
impost on those articles become less productive; and when this takes
place, Government, no doubt, will share in the profits, by levying a tax
on the new lights. The Exchequer will thus have nothing to fear; as one
branch of the revenue fails, another, and a more productive one, will
supply its place.

Upon the whole, when we reflect that the object of the gas-light
illumination is to open a source of national wealth, of which nothing
can deprive us, to create, we may almost say, new articles of value, its
friends cannot be thought guilty of great presumption, if they look
forward with confidence to the successful extension of this new art of
civil economy; and if, contrary to all expectations, the effects of
jealousy and prejudice should, in some respect or other, continue here
and there its influence against this new art of procuring light, a firm
perseverance of its application must at length remove that ignorance
which alone can give them birth.


TABULAR VIEW, EXHIBITING

  The quantity of GAS, COKE, TAR, PITCH, ESSENTIAL OIL, and AMMONIACAL
  LIQUOR, obtainable from a given quantity of COAL; together with an
  Estimate of the quantity of Coal necessary to produce a quantity of
  Gas, capable of yielding a Light equal in duration of time and
  intensity to that produced by Tallow Candles of different kinds.

  -----------+------------------------------------------
             |            _Cost of Coal._
             | Minimum.     Maximum.          Average.
  -----------+------------------------------------------
  One Chal. }|
  of Coal,  }|  40_s_       to 60_s_      -- 50_s_
  from 25 to}|
  28 cwt.   }|
  One Ton    |  30_s_       to 48_s_      -- 38_s_ 6_d_
  One Sack   |   3_s_ 4_d_  to  5_s_      --  4_s_ 2_d_
  One Bushel |   1_s_ 2_d_  to  1_s_ 8_d_ --  1_s_ 5_d_
  One Peck   |        3-1/2 to  5_d_      --       4-1/4
  One Pound  |                                       1/4
  -----------+------------------------------------------

  -----------+-----------------------------------
             |       _Weight of Coal._
             |  Min.       Max.         Aver.
  -----------+-----------------------------------
  One Chal. }|
  of Coal,  }| 2,800    to 3,136     -- 2,968
  from 25 to}|
  28 cwt.   }|
  One Ton    |                          2,240
  One Sack   |  233     to   261     --   247
  One Bushel |   78     to    87     --    82-1/2
  One Peck   |   19-1/2 to    21-1/4 --    20-1/4
  One Pound  |                              1
  -----------+-----------------------------------

  -----------+--------------------------------
             |_Produce of Gas, in cubic feet._
             |  Min.     Max.        Aver.
  -----------+--------------------------------
  One Chal. }|
  of Coal,  }| 8,906 to 11,872     10,388[39]
  from 25 to}|
  28 cwt.   }|
  One Ton    | 6,720 to  8,960 --   7,840
  One Sack   |   741 to    988 --     814
  One Bushel |   247 to    330 --     290
  One Peck   |    61 to     82 --      71-1/2
  One Pound  |     3 to      4 --       3-1/2
  -----------+--------------------------------

  -----------+-----------------------------------------
             | }               |_Candles._
             | }               |9,516  11 to the pound.
  One Chal. }| }[39]Equal to   |8,651  10      do.
  of Coal,  }| }as many tallow |7,786   9      do.
  from 25 to}| }candles, 12 in |6,921   8      do.
  28 cwt.   }| }the pound,     |6,556   7      do.
             | }burning two    |5,194   6      do.
  One Ton    | }hours; or to   |4,325   5      do.
  One Sack   | }               |3,463   4      do.
  One Bushel | }               |2,595   3      do.
  One Peck   | }               |1,730   2      do.
  One Pound  | }               |  866   1      do.
  -----------+-----------------------------------------

  COKE.--One chaldron of coal, from 25 to 28 cwt. gives 1-1/4 to 1-1/2
  chaldron of Coke.

  TAR.--One chaldron of coal, from 25 to 28 cwt. gives from 150 to
  180lb. of Tar,[39] or 15 to 18 ale gallons, 10lb. each.

  AMMONIACAL LIQUOR.--One chaldron of coal, gives from 220 to 240lb. of
  Ammoniacal Liquor, or 22 to 24 ale gallons.

  [39] 1000lb. of Coal-Tar afford by distillation, from 260 to 265lb. of
  Essential Oil, or Naphtha. 1000lb. of Coal-Tar produce by mere
  evaporation, from 460 to 480lb. of Pitch.

_Tabular View, exhibiting the illuminating power of Coal-Gas, compared
with the illuminating power of Tallow Candles of different sizes._

  One chaldron of Coal produces, according to weight and quality,
   Cubic feet of Gas.  Average. Burning. Candles. 12 to 1lb. 6 to 1lb.
  From 9,000 to 12,000  10,500  1 hour      =       21,000  = 10,500
       -----    ------  ------  2 hours     =       10,500  =  5,250
       6,000    8,000   7,000   3 ditto     =        7,000  =  3,500
       4,500    6,000   5,250   4 ditto     =        5,250  =  2,625
       3,600    4,800   4,400   5 ditto     =        4,400  =  2,200
       3,000    4,000   3,500   6 ditto     =        3,500  =  1,750
       2,571    3,428   3,005   7 ditto     =        3,005  =  1,502
       2,250    3,000   2,625   8 ditto     =        2,625  =  1,312
       2,000    2,666   2,333   9 ditto     =        2,333  =  1,166
       1,800    2,100   2,100  10 ditto     =        2,100  =  1,050
       1,636    2,191   1,913  11 ditto     =        1,913  =    956
       1,500    2,000   1,750  12 ditto     =        1,750  =    875
       1,384    1,846   1,615  13 ditto     =        1,615  =    807
       1,285    1,714   1,499  14 ditto     =        1,499  =    749
       1,200    1,600   1,400  15 ditto     =        1,400  =    700
       1,125    1,500   1,312  16 ditto     =        1,312  =    656
       1,058    1,111   1,234  17 ditto     =        1,234  =    617
       1,000    1,333   1,166  18 ditto     =        1,166  =    583
         947    1,263   1,105  19 ditto     =        1,105  =    552
         900    1,200   1,050  20 ditto     =        1,050  =    525
         857    1,143   1,000  21 ditto     =        1,000  =    500
         818    1,095     956  22 ditto     =          956  =    478
         783    1,044     913  23 ditto     =          913  =    456
         750    1,000     875  21 ditto     =          875  =    437

N. B. If it be required to know, for how many hours one pound, or one
peck, or one bushel, or one sack, of coal will produce Gas Light equal
to that of a certain number of well-snuffed Tallow Candles, the
proportion of each of the average weights of a pound, peck, bushel, or
sack, to that of the average weight of a chaldron of coal, is as
follows:

               1 lb. = 2968th part of a chaldron.
  One peck    20     = 148th        ditto.
  One bushel  82     =  36th        ditto.
  One sack   248     =  12th        ditto.

RULE.--Divide with either of the above parts of weight, the number of
lights opposite to their hours, and the product will be the number of
lights burning for the same number of hours.

EXAMPLE.--To know how many lights one peck of coal will give for six
hours, divide the 148th part in 3,500, opposite to the number of six
hours, the product is almost 24 lights. The same rule holds good for any
given quantity or number of pounds of coal, in a chaldron, to find how
many lights, or candles, 12 to the lb. or 6 to the lb. they will give
for a given number of hours.


DESCRIPTION OF THE GAS-LIGHT APPARATUS.


PLATE I.

Exhibits a perspective view of a gas-light apparatus,[40] for lighting
factories, or small districts of houses. It consists of the following
parts: which may be considered separately.

  [40] This apparatus was erected by Mr. CLEGG, and is now in action at
  Mr. ACKERMAN's establishment, in this metropolis.

FIG. 1. The _Retort Furnace_, for distilling the coals. It is built of
brick-work. The bricks which are exposed to the immediate action of the
fire, are _Welch tumps_, or fire-bricks; they are bedded in clay, or
Windsor loam.

FIG. 2. The _Tar Cistern_, to collect the coal-tar, and other
condensible products obtained during the distillation of the coals. It
is a cast-iron hollow cylinder, closed at the top with a cast-iron
cover, which has a very small hole to allow the air to escape as the
liquid enters into the vessel.

FIG. 3. The _Lime Machine_, for purifying the crude coal-gas, and to
render it fit for use. The construction of this machine will be
explained in plate VII. It is put together of cast-iron plates.

FIG. 4. The _Gasometer_, for collecting and preserving the purified gas,
and for distributing and applying it as occasion may require. It
consists of two principal parts--namely, a large interior vessel closed
at the top and open at the bottom, made of sheet iron, designed to
contain the gas, and an outer cistern or vessel, of rather greater
capacity, constructed of cast-iron plates, in which the former vessel is
suspended. The latter contains the water by which the gas is confined.
The interior vessel which contains the gas is suspended by chains hung
over wheels or pullies, to which weights are attached, so as to be just
sufficient to balance the weight of the gasometer, all but a small
difference, and allowing its slow descent in the manner which is found
as nearly adapted as can be to the proper supply of the lamps. The
weight of the chains must be equal to the specific gravity of the
material of which the gasometer is composed, so as to compensate
accurately for the quantity of water which the gasometer displaces, or
what is the same, it must be equal to the loss of weight which the
gasometer sustains, when immersed in the water; and the counterpoise
weight must be equal (or nearly so) to the absolute weight of the
gasometer.

The action of these different parts of the apparatus will be obvious
from the following explanation:

A, A, are two iron retorts, placed horizontally, and side by side, in
the furnace; the mouth of the retorts where the coals are introduced,
projects into an arched chamber, situated in front of the furnace, as
shewn in the drawing by the broken down brick-work. The object of
suffering the mouth of the retorts to project into a separate chamber,
is merely to discharge with convenience the red hot coke from the
retorts when the process is at an end; the coke being suffered to fall
to the bottom of the chamber, where it cools, without becoming
troublesome to the operator. It may be removed from this fire-safe
chamber by the door represented at the end view of the furnace.

When the operation commences, the inner vessel of the gasometer, fig. 4
is sunk down, to expel the air which it contains to a level with the
exterior vessel, or outer cistern, of the gasometer; and, consequently,
becomes filled with water. As the distillation of the coal in the
retorts proceeds, the liquid and gazeous products evolved from the coals
are transmitted by means of the perpendicular syphon pipes B, B, into
the horizontal pipe or main condenser C, with which they are connected.
The liquid which is distilled, collects in the pipe, or main condenser,
C, where it is retained until its quantity has risen so high as to
discharge itself into the pipe D, which is connected with the upper part
of one of the extremities of the condenser, C. One of the extremities of
the pipes, B, B, therefore become immersed into the liquid contained in
the main condenser or pipe C, whilst the vaporous or condensible fluid,
after having overcome the pressure there opposed to it, is transported
into the pipe E, which, after passing in a serpentine direction, E, E,
&c. through the exterior vessel or cistern of the gasometer, terminates
in the tar-vessel, fig. 2. Thus the vaporous fluids are condensed by
passing through the serpentine pipe, E, E, &c. and become deposited in
the tar-cistern, fig. 2; whilst the non-condensible or gazeous products
are made to proceed by the pipe F, which branches off from the pipe E,
into the lime machine, fig. 3. In this apparatus the gas, as it is
evolved from the coals, comes into contact with slaked lime and water;
the object of which is, to strip it of its sulphuretted hydrogen and
carbonic acid gas with which it always abounds, and to render it fit for
illumination. This being accomplished, the purified gas is conducted
away out of the lime machine by means of the pipe G, into the
perpendicular pipe H, which branches up through the bottom of the
gasometer cistern. The upper extremity of this pipe is covered, in the
manner of a hood, by a cylindrical vessel I, open at bottom, but
partially immersed beneath the surface of the water contained in the
outer cistern of the gasometer, it is also perforated round near the
lower edge with a number of small holes. The gas, as it passes out of
the pipe H, displaces the water from the receiver I, and escapes through
the small holes, and is thus made to pass through the water in the
cistern, in which the hood of the pipe I, is partly immersed, so as to
expose a large surface to its action, that it may once more be washed,
and deprived of all the foreign gazeous products which might have
escaped the action of the lime, whilst it was agitated with this
substance in the lime machine, fig. 3. After rising through the water in
the gasometer cistern, it enters into the gasometer, which then ascends
as the gas accumulates in it.

In this manner the process proceeds, until the whole of the volatile
products of the coal in the retort are disengaged. The use of the
gasometer is, partly to equalize the evolution of the gas which comes
from the retort more quickly at some time than others. When this
happens, the vessel rises up to receive it, and when the stream from the
retort diminishes, the weight of the gasometer expels its contents,
provided the main-cock be open. When the process is finished, the retort
is suffered to cool, and its lid is then removed to replenish it with
coal. When the main stop-cock is then opened, the gasometer descends,
and the gas passes from the gasometer through the pipe K, to the
burners, or main pipe, which communicates with the gas burners or lamps.
L, is a wooden tub or barrel, containing the mixture of lime and water,
for charging the lime machine; and into which the contents of the
barrel, L, may be conveyed by the curved pipe M, without admitting
common air. N, N, is a water-pipe, to convey fresh water into the
gasometer cistern occasionally; because it is essential that the water
used for washing and purifying the gas should be changed for fresh as
soon as it becomes dirty; and unless this is done, the gas will not be
perfectly purified by washing, but produce a disagreeable odour when
burnt; the same holds good with regard to the lime machine, the
contents of which should be renewed occasionally. This pipe also conveys
the necessary water into the barrel, L. O, is a waste-pipe, to convey
the water as it becomes impregnated with the impurities of the gas, out
of the gasometer cistern. P, is an agitator, to stir up the contents of
the lime machine occasionally, Q, Q, are two iron rods, which serve as
stays to guide the motion of the gasometer. R, is an index, connected by
means of a shaft and pulley with the axis of one of the gasometer
wheels. This index is graduated to the capacity of the cubical contents
of the gasometer, so as to indicate, by the rising and falling of the
gasometer, its relative contents of gas expressed in cubic feet. S, is
the waste pipe of the lime machine, to remove the insoluble parts of the
lime. T, represents the iron cover, or lid, which is turned on the
lathe, and ground air-tight, to close up the mouth of the retort, so as
to make readily an air-tight fitting. U is an iron wedge to secure the
cover of the retort. The left-hand retort in the design shows the retort
closed up, and the cover, or lid of the mouth of it secured by means of
the wedge, in its place, so as to render the mouth of the retort
perfectly air tight.

There is a safety valve attached to this gasometer which could not be
represented in the drawing; and the object of which is, to convey away
any portion of gas that might happen to be produced by a careless
operator, when the gasometer is full, and which is thus prevented from
accumulating in the place where the gasometer is erected. It is
represented in the right-hand corner of plate VII. where fig. 1 shows
the edge of the gasometer; 2, the surface of the water in the inside of
the gasometer; 3, the surface of the water in the outside of the
gasometer, or in the cistern; 4, a pipe issuing from the lower edge of
the gasometer, and surrounded at its upper extremity with a cup marked
5; 6, the waste pipe, the mouth of which is immersed in water. It is
obvious that, when the gasometer is full, if an additional quantity of
gas should be attempted to be put into it, it will be transported by
means of the pipe 4, into the waste-pipe 6; the upper extremity of which
reaches out of the building, and there communicates with the open air.


PLATE II.

Represents a Portable experimental Gas Apparatus for exhibiting, in the
small way, the general nature of the gas-light illumination.--It is
described page 79.


PLATES III. IV. V.

Show designs of various kinds of Gas Lamps, Chandeliers, Candelabras,
&c.--See pages 114, 118, 140.


PLATE VI.

FIG. 1. Exhibits a design of the _gasometer framing_, or _skeleton_,
which serves to give stability and strength to the gasometer. It
consists of wooden frame work, marked A, A, A, interlaced with iron
rods, B, B, B, &c. The whole framing is so disposed that it will float
in the cistern horizontally, and therefore keep the gasometer perfectly
steady and level with the surface of the water.

The rest of the sketches represent various kinds of gas pipes employed
as _mains_ for conveying the gas, and the methods of connecting them.

FIG. 2. Represents a longitudinal section of a _Spigot_ and _Faucet
Pipe_. These kinds of pipes are applicable in most cases as mains for
conveying gas. A, is called the spigot, and B, the faucet. They are
joined together, and made air tight, by iron cement, the composition of
which is as follows:

Take two ounces of sal ammoniac, one ounce of flowers of sulphur, and
sixteen ounces of cast iron filings or borings. Mix all well together,
by rubbing them in a mortar, and keep the powder dry.

When the cement is wanted for use, take one part of the above powder,
and twenty parts of clean iron borings or filings, and blend them
intimately by grinding them in a mortar. Wet the compound with water,
and when brought to a convenient consistence, apply it to the joints
with a wooden or blunt iron spatula.

By a play of affinities, which those who are at all acquainted with
chemistry will be at no loss to comprehend, a degree of action and
re-action takes place among the ingredients, and between them and the
iron surfaces, which at last causes the whole to unite as one mass. In
fact, after a time, the mixture and the surfaces of the flanches become
a species of pyrites (holding a very large proportion of iron,) all the
parts of which cohere strongly together.

The inner parts of the faucet ought to be no larger in diameter than
just to fit the spigot. This supports the pipe, independently of the
cement, and prevents the risk of hurting the joint from any external
stress. The inner faucet is commonly made about 2-1/2 inches deep, and
has the spigot inserted 1-1/2 inch into it. The practice of some
workmen, is to make the outer faucet, or that which contains the cement,
six inches deep, for all pipes above six inches diameter; and to make
the faucets of all pipes below six inches, the same depth as the
diameter of the pipes. It is usual to make the space for the cement, all
round the spigot, from 1 to 1-1/2 inch; that width is required, in order
that the cement may be firmly driven into the joint. When the space is
very narrow, this cannot be done. On the other hand, when too wide,
there is a waste of cement, and a risk of injury from unequal expansion.

FIG. 3. Exhibits a profile view of these kinds of pipes when joined
together. The spigot and faucet pipes are liable to burst from the great
expansion of the spigot, and the risk of this accident is increased by
increasing the space between the spigot and faucet, which requires to be
filled with cement.

FIG. 4. Represents a longitudinal section of two flanch pipes, and the
modes of connecting them. A and B, show the parts of the pipes; and C
and D, the flanches. These pipes are also joined together, and rendered
air-tight, by interposing between the flanches rope-yarn, hemp, or some
other pliable material, and iron cement, and then screwing up the faces
of them by means of the bolts and screw nuts.

FIG. 5. Profile view of the same kind of pipes connected together, A and
B, the pipes; C and D, the flanches; E and F, the bolts.

FIG. 6. Represents the method of joining spigot and faucet pipes when
they are to have a turn or angle. This method is convenient when the
place where the turn required to be made is previously known, and the
pipes cast accordingly.

FIG. 7. Exhibits the method of connecting spigot and faucet pipes when
they have a round turn. A and B, the junctures of the pipes.

FIG. 8. Represents a longitudinal section of the mode of joining pipes
by means of what is called a _thimble joint_. The junctures of the pipes
to be connected, are made air tight, as mentioned already, by iron
cement. A, the thimble or small cylinder, with projecting edges, which
unites the pipes B, C.

FIG. 9. A thimble joint made in two parts, which is sometimes convenient
to join pipes. The parts are joined together by screw bolts, and nuts,
in the usual manner.

FIG. 10. Section of the same.

FIG. 11. Represents a profile view of what is called the _saddle joint_.
It is employed for taking off a branch-pipe. The branch has a piece A B,
formed on its end, and fits round one-half of the outside of the pipe
from which it is to proceed. C, is called the saddle, which fits round
the other half of the pipe. The parts are secured together by screw
bolts, and iron cement. By this method a branch may be formed on any
part of a gas-pipe, by cutting a hole there, and applying the branch to
that place. Where there is much risk of the inequality of expansion, the
joints at certain places, should be secured by a soft stuffing of hemp
and tallow; but in most cases the joints may be made with iron cement.
Lead is frequently used for making the joints of gas pipes instead of
iron cement, though cheaper and more easy of repair. The galvanic action
which takes place between the lead and iron, soon renders the joints
leaky, and the danger is increased by the unequal expansion of the two
metals.

FIG. 12. Section of the saddle-joint.

Before the gas is suffered to enter into the pipe, they should be proved
to be sound, by the usual process of forcing water into them: The pipes
serving as mains, are placed perfectly solid, so that they cannot give
way; their course should be rectilinear, having a descent of about 1
inch in 9 or 10 feet, to allow the water of condensation which may be
deposited from the gas by a change of temperature to collect readily at
the lowermost part.

FIG. 13. Shows a reservoir for collecting the water of condensation
which might accumulate in the pipes. It consists of a receptacle, A, in
which the water may pass; B, a branch-pipe closed at the top, by means
of which the water may be removed, by drawing it out with a syringe.
This receptacle is placed in those situations where pipes incline
towards each other.


PLATE VII.

Exhibits a perpendicular section of a gas-light apparatus, calculated
for lighting towns, or large districts of streets and houses.

FIG. 1. The Retort Furnace. The retorts are placed over each other in
one or more rows; so that a certain number of them may be heated by
separate fire-places. A, A, shows two of the retorts placed horizontally
above each other; B, the fire-place; C, the flue which causes the fire
to circulate round the retorts so as to heat them equally in every part;
D, the opening of the flue where the fire passes into the chimney; E,
the ash-pit; F, a chamber in front of the retort furnace, into which the
orifice or mouth of the retorts project; G, G, the doors of the chamber,
to enable the workmen to charge and discharge the retorts; H, a funnel
shaped hole at the floor of the chamber F, through which the red hot
coke as it is discharged from the retorts passes into the arched vault
I; K, the syphon tube; L, the horizontal condenser[41]--the action of
both of these pipes have been already explained, p. 168; M, main pipe,
which conveys the liquid substances from the condenser, to the tar
cistern, fig. 3, and which conducts also the gazeous products into the
lime machine, fig. 2; N N, shows that part of the pipe which is
interposed between the tar cistern, fig. 3, and the condensing pipe
M,--it passes in a serpentine direction along the inner sides of the
gasometer cistern, and, like the so-called _worm_ in a distillatory
apparatus, condenses the products which escape in a vaporous state from
the condenser L; O, shows the place where the serpentine pipe N N,
passes again out of the gasometer cistern, and its communication with
the lime machine, fig. 2, and tar chamber, fig. 3. The action of the
lime machine is as follows: The liquid products evolved from the coal,
having been deposited in the tar cistern, fig. 3, by means of the
serpentine pipe N, N, the gazeous products which accompany it, are
conveyed by means of the pipe P, which branches out from the pipe O,
into the interior receptacle of the lime machine marked Q, which
consists of a vessel open at the bottom, and closed at the top, where it
communicates with the pipe O. As the gas accumulates in the interior
part Q, of the lime machine, it is made to pass through the liquid which
it contains, namely, slaked lime and water; and escapes through
appertures made in the horizontal partitions R, R, R, R, into the outer
vessel, S, of the lime machine and from thence it is conducted away by
the pipe T, T, T, into the additional washing apparatus, of the
gasometer; fig. 4, the construction of this apparatus, greatly resembles
the lime machine, fig. 2, namely, V, is a water pipe, proceeding from a
cistern U, placed 3 or 4 feet above the orifice of the pipe V; T, T, is
the gas-pipe, covered with a hood, marked W, and immersed in a small
cistern, having horizontal perforated shelves, like those in the lime
machine--they fit close to the hood. The gas which enters the hood W,
meets with a shower of water delivered by the pipe V. The gas, as it
passes through the holes in the horizontal partitions, is, therefore,
again washed and thoroughly purified from foreign gases which may have
escaped the action of the lime machine; Y, is a waste pipe, the lower
extremity of which is sealed by being immersed in water,--it serves to
carry away the water delivered by the pipe V, as it has been acted on by
the gas. The summary action of this gas apparatus is, therefore, as
follows: The liquid products obtained from the coal during the
distillation are first deposited in the main condenser L, by means of
the pipe K, and from whence they cannot escape until a quantity of tar
has accumulated in it to a certain height, and by this means, one of the
extremities of the pipes K, K, becomes immersed and hermetically sealed
by the liquid which the condenser L, contains. The liquid products,
after having accumulated to a certain height in the condenser, overflow
the perpendicular portion which it contains, and discharge themselves
into the pipe M, from whence they are transported into the tar cistern,
fig. 3, by means of the system of pipes N, N, O, whilst the gazeous
products are made to pass by means of the branch pipe P, into the lime
machine, fig. 2. From this part of the apparatus the gas passes through
the pipe T, T, T, into the additional or smaller washing apparatus
placed upon a tressel in the cistern of the gasometer, where it is
again exposed a second time to the action of a current of fresh water;
and from this vessel the gas ascends into the gasometer. The gasometer
is furnished with a pipe A, closed at the top, and fixed in one corner
of the gasometer, but open at the bottom; it includes another pipe
marked B, which communicates with the main pipe leading to the burners,
or place where the gas is wanted. The pipe A, which slides over the pipe
B, is perforated at the top, the gas passes through these perforations
and is thus made to enter into the pipe B, and disposed of as mentioned.
C, C, is a tube of safety adapted to the gasometer; its lower extremity
remains sealed by the water in the cistern so long as the gasometer is
not overcharged with gas; but, if more gas should be made to enter the
gasometer than it is destined to receive, this pipe then delivers the
gas into the funnel-shaped tube D, which reaches through the roof of the
gasometer house, and thus the superfluous quantity of gas is conveyed
away into the open air.

  [41] The condenser in this apparatus is placed at right angles to the
  row, or rows of retorts. It is furnished at one extremity with a
  partition placed perpendicularly, and of a height equal to about
  one-half of the diameter of the condenser. The object of this
  partition is to prevent the tar, &c. deposited in it, to seal the
  pipes K, K, and not to discharge itself into the pipe M, till this has
  been effected. The partition is seen in the drawing.

The cylindrical vessel P, of fig. 3, surrounding the orifice of the pipe
O, which delivers the tar into the tar cistern, fig. 3, serves to keep
this pipe constantly immersed into a portion of tar, so that the
contents of the cistern may be drawn off by the cock without admitting
air into any part of the apparatus. The tar cistern has a small hole at
the top, to allow the air which it encloses to escape, as it becomes
filled with tar and ammoniacal liquor. The main condenser L, is placed,
as shown in the drawing, higher than the level of the water in the
gasometer cistern, to allow a free descent of the distillatory liquids
as they pass from this vessel along into the pipes M, N, O, &c. The
cistern of the gasometer, as well as the lime machine, and tar cistern,
are constructed of cast iron plates, bolted and cemented together with
iron cement. The gasometer is made of sheet iron plates rivetted
together--E, E, are two iron stays--G, G, are friction wheels.


_METHOD of correcting the relative pressure of the Gasometer, so as to
cause the gas which it contains to be uniformly of an equal
density._[42]

  [42] For this elegant contrivance we are also indebted to Mr. CLEGG.

We have mentioned already that the pressure of the gas in the gasometer
should be invariable, for it is obvious that the weight of the gasometer
is constantly increasing in proportion as it fills with gas, and rises
out of the water--see p. 88, and 167. To render its pressure uniform, we
first take the _absolute_ weight of that part of the gasometer which
becomes immersed in the water, and knowing the _specific weight_ of the
substance of which it is composed, we divide its absolute weight by the
specific weight of the substance of which it is composed; and this being
done, we make part of the chain, (measured at right angles from the axis
of the wheels over which it passes downwards towards the top of the
gasometer,) which is equal to the length of that part of the gasometer
which becomes immersed in water, equal in weight to the specific gravity
of the substance of which the gasometer is composed. For example, let
us suppose that the part of the gasometer which becomes immersed in
water weighs 861 _lb._ and that it is composed of sheet iron, the
specific gravity of which, in round numbers, we will take to be 7. It is
then evident, that the part of the chain of the gasometer measured
downward from the axis of the wheel over which it passes, and which is
equal in length to the height of the gasometer, must be loaded with a
weight of, or must itself weigh, 123_lb._ for this would be the weight
of the water displaced by the gasometer; or let us suppose the gasometer
to be made of sheet copper, the specific weight of which (omitting
decimals) is 8; and that the absolute weight of the gasometer is
1792_lbs._ then the chain of the gasometer equal in length to the height
of the gasometer, immersed into the water must weigh 224_lb._ for this
would be the weight of the quantity of water which the gasometer
displaces. This being accomplished by then adding or diminishing the
absolute or balance weight of the gasometer, any desired uniform
pressure may be effected, and the same bulk of gas will always be of the
same specific gravity.


DIRECTIONS TO WORKMEN ATTENDING THE GAS-LIGHT APPARATUS[43].

  [43] Copied from a printed direction drawn up by Mr. Clegg, for the
  use of workmen.

Particular care must be taken to make the joints of the mouth-pieces of
the retorts perfectly air tight, which may be done in the following
manner:--Take some common clay, dry, pulverize, and sift it, then add
as much water as will make it into the consistency of treacle; make the
mouth-piece and the lid of the retort clean, lay this luting thinly over
the turned part of the lid, press the lid so luted gently to the
mouth-piece, and then secure it moderately, by means of the iron wedge:
if the workman observes this rule, he will never fail to make good
joints; but if, on the other hand, the operator is careless and neglects
to remove the old luting, &c. from the turned or smooth part of the
mouth of the retort, and thereby cause a bad joint, the consequence will
be the loss of a considerable quantity of gas, and a very disagreeable
smell and smoke.

The bridge or row of bricks of the flue C, of the retorts, should never
be made hotter than a bright red, which may be regulated by the door of
the ash-pit being kept close shut when the fire is getting too hot. If
the operator neglects this, and suffers the fire-bricks to arrive at a
bright white heat the retorts will soon be destroyed, and bad gas be
produced.

The gasometer should be well examined, at least once a week, to see if
it leaks, by the following method, viz. Let the main stop-cock be shut,
then make a mark on the gasometer at the water's edge when it is full or
nearly of gas, there being no gas coming from the retorts at the time,
and if the mark sinks in the water, the gasometer leaks; to find out the
place, walk slowly round it, and you may perceive the leak by the smell,
apply a lighted candle to the part suspected, and if there be gas
issuing from it, it will take fire, and perhaps appear like a small
blue flame--blow it out, and mark the place: thus proceed round the
gasometer till you have found all the places; if you perceive a smell,
and yet cannot produce a flame in the part suspected, take a brush with
a little thin white-lead paint, and lay it on the part where you think
the leak is, and, if it be there, the gas which escapes from the leak,
will immediately turn the paint brown. After the sides of the gasometer
have been well examined, and secured by dipping a piece of cloth about
the size of a shilling, into some melted pitch, tempered with a little
bees-wax and tar, apply the cloth whilst hot to the place with the end
of your finger, rubbing it till it is quite cold; next examine the top
of the gasometer in the same manner,--when it is about two feet high in
the cistern, it will then be better to get at. The water in the cistern
should always be kept within 3 or four inches of the top, if suffered to
sink much lower without replenishing, the gas will not pass through a
sufficient quantity of water, and oily particles will be apt to condense
in the pipes, to their great detriment.

The only thing to be observed in the place lighted is, that the lamps
and pipes are not suffered to be touched on any pretence whatever, but
by the person entrusted with their care. When a lamp is not wanted, it
must be completely shut off from the pipe which supplies it, by a
stop-cock provided for the purpose, and not opened again but when a
flame is held over it; not a lighted candle, as the tallow is liable to
drop into the lamps; lighted paper is better.


ESTIMATE OF THE PRICE OF A GAS-LIGHT APPARATUS, _IF ERECTED IN LONDON_,

Capable of affording, every 24 hours, Light equal to 40,000 Tallow
Candles, six in the pound, burning one hour.

                                                            L.  s.
  Gasometer, to contain 10,000 cubic feet of gas            236  0

  Wheel-work, regulating chain, ballance-weight for }       160 11
    ditto, with wooden framing                      }

  Wrought iron cistern for gasometer--36 feet wide, }       500  0
    24 feet long and 16 feet deep                   }
      (_It would weigh about 16 tons._)

  Wooden framing built around it, to secure ditto           150  0

  Condenser, cistern and communicating pipes                126  0

  Lime machine, made of cast iron plates                     82  0

  Gasometer-house, built of frame-work and weather-boarded  250  0

  Twenty-four retorts set in brick-work, with furnaces }    336  0
    for ditto, compleat                                }

                        Sundries                            100  0
                                                         ---------
                                                         L 1940 11

       *       *       *       *       *

  A gas-light apparatus complete for work, capable of affording every
  twenty-four hours a quantity of light equal to 1,400 Argand's Lamps,
  each lamp equal in intensity to six candles, six in the pound, burning
  for five hours, will cost 3,500_l._ if erected in this metropolis.


LONDON Price List of the most essential articles[44] employed in the
erection of a Gas-Light apparatus.

  [44] All the articles are warranted to be perfect and of the best
  kind. They are delivered free of expence at any wharf between London
  and Westminster-bridge.

                 Sheet-iron pipes brazed.
                                             _s._ _d._
      1/4 inch in diameter                    0    4    a foot}
      3/8 ditto                               0    4     ditto}
      1/2 ditto                               0    5     ditto}
      5/8 ditto                               0    6     ditto}
      3/4 ditto                               0    6-1/2 ditto} in
      7/8 ditto                                    7     ditto} 15
    1 inch, ditto                             0    7-1/2 ditto} to
    1-1/4 ditto                               0    9     ditto} 18
    1-1/2 ditto                               0   10-1/2 ditto} feet
    1-3/4 ditto                               0   11     ditto} lengths.
    2 inch, ditto                             1    1-1/2 ditto}
    2-1/4 ditto                               1    4     ditto}
    2-1/2 ditto                               1    5     ditto}
    3 inch, ditto                             1    6-1/2 ditto}
    Copper pipes brazed 1/4 inch              0    4 per foot
    Ditto, ditto, ditto 3/8 inch              0    5-1/2 ditto
    Gas-light cockspur burners with stop-cock 2s 6d to 3s 6d
    Argand's lamps, with glass-holders, from 3s to 4s 6d
  Cast-iron retorts, weighing 7 cwt. at 15s 6d per cwt L5  8 6
  Mouth-piece for ditto, compleat                       1 14 8
  Cast-iron door frames for retort furnace              1  0 0
  Furnace bars 10s. per cwt.
  Sheet iron for gazometer (No. 23) 24s. per cwt.
  Gazometer chains, 5d per lb.
  Ballance weights [Plates] for gazometer, 9l 10s per ton.
  Cast-iron cistern plates
  ------------------------ smaller size for lime machine, 18l per ton.
  ------------------------ middling size for tar cistern, 16l ditto
  ------------------------ largest size for gazometer cistern 14l ditto
  Cast-iron flanch pipes 2-inch diameter, at 5s per yd. in 6 feet lengths
          ditto          3      ditto        6s      ditto 6      ditto
          ditto          4      ditto        8s 6d   ditto 9      ditto
          ditto          5      ditto       10s      ditto 9      ditto
          ditto          6      ditto       12s      ditto 9      ditto
          ditto          7      ditto       13s 6d   ditto 9      ditto
          ditto          8}
          ditto          9} 11l. 5s. per ton               9      ditto
          ditto         10}
          ditto         11}
  1/2 inch nuts, screws and washers to put iron pipes together 7d. per lb
  5/8 ditto                                                    7d. ditto
  3/4 ditto                                                    6d. ditto
  English bar-iron                                            13l. per ton
  Best, ditto                                                 18l. ditto


_FINIS._

[Illustration: Fig. 1

_London Pub. April 1-1815, at R.Ackermann's, 101 Strand._]

[Illustration]




Transcriber's notes

The entries in the Table of Contents do not always conform to the
chapter and section headings in the text. Both have been retained as in
the original work.

The errata have already been incorporated in the text; the error
mentioned as occurring on page 24 actually occurs on page 22.

The original language, including inconsistencies in spelling,
hyphenation, punctuation, formatting, etc. has been retained, except as
mentioned below.

Unclear parts of the text have been checked against the on-line copy of
this book of the Eidgenoessische Technische Hochschule Zuerich.

Fractions like 1/2 and 1-10th have both been retained.

Page 90, Van Dieman, Troostwyck: Jan Rudolph Deiman and Adriaan Paets
van Troostwijk.

Changes made to the text:

Obvious punctuation and typographical errors have been corrected
silently.

Some footnotes, tables and illustrations have been moved; some tables
have been re-arranged.

Other changes:

Page 23: any surfaces changed to any surface

Page 26: opening or shuting changed to opening or shutting

Page 47: A New changed to A new

Page 48: trafic changed to traffic; footnote [10]: corporated changed to
incorporated (cf. errata)

Page 53: This combustion changed to The combustion (cf. errata)

Page 64: Cleg changed to Clegg (cf. errata); footnote anchor [14] moved
from next page (cf. errata, footnote anchor *); communicates changed to
communicated (cf. errata)

Page 67: 1250 + 2 = 2500 changed to 1250 x 2 = 2500

Page 69: Mr. LEE changed to "Mr. LEE for consistency

Page 72: closing quote mark added to letter

Page 96: pure coal- changed to pure coal-gas

Page 102: sub acetate changed to sub-acetate

Page 118: ball 6 changed to ball _b_

Page 119: _e_, are changed to _e_ _e_, are

Page 125: 180 degree changed to 180 degrees (cf. errata); footnote [28]:
may he compleatly changed to may be compleatly

Page 131: and make changed to and makes

Page 132: coal changed to coal-tar (cf. errata)

Page 158: Nortou Falgate changed to Norton Falgate; a about changed to
about

Page 165, table: 10,509 changed to 10,500.





End of the Project Gutenberg EBook of A Practical Treatise on Gas-light, by
Fredrick Accum

*** 