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+Project Gutenberg's A Practical Treatise on Gas-light, by Fredrick Accum
+
+This eBook is for the use of anyone anywhere at no cost and with
+almost no restrictions whatsoever.  You may copy it, give it away or
+re-use it under the terms of the Project Gutenberg License included
+with this eBook or online at www.gutenberg.org
+
+
+Title: 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.
+
+Author: Fredrick Accum
+
+Release Date: January 2, 2014 [EBook #44567]
+
+Language: English
+
+Character set encoding: UTF-8
+
+*** START OF THIS PROJECT GUTENBERG EBOOK A PRACTICAL TREATISE ON GAS-LIGHT ***
+
+
+
+
+Produced by Chris Curnow, Harry Lamé and the Online
+Distributed Proofreading Team at http://www.pgdp.net (This
+file was produced from images generously made available
+by The Internet Archive)
+
+
+
+
+
+
+
+Transcriber’s notes
+
+Italics in the original work are transcribed between _underscores_;
+small-capitals have been transcribed as all capitals.
+
+More transcriber’s notes and a list of corrections made may be found at
+the end of this text.
+
+
+[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 LINNÆN SOCIETY, MEMBER
+  OF THE ROYAL ACADEMY OF SCIENCES OF BERLIN, &c. &c.
+
+  WITH SEVEN COLOURED 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    1½  |  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   15¾  |  1     |    8    |
+  |   3      {|    3   |  3  0  | 1    2   |  1⅛    |    8¾   |
+  |          {|  Mould |  3  0  | 0    0   |  1     |    9    |
+  +-----------+--------+--------+----------+--------+---------+
+  |   4      {|    5   |  3  0  | 1    5   |  1.18  |    8¾   |
+  |          {|  Mould |  3  0  | 1    1⅛  |  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_² : Q ∷ _b_²
+  : (_b_² + Q)/_a_² = 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_² + Q)/_a_² (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° 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°, 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| 18¾     |  0  14    | 3   15 | 59   26  |     9.70        |
+  |wick.  | 19      |  0  13½   | 2   40 | 50   34  |    11.40        |
+  |A large| 16½     |  0  15½   | 2   40 | 44    2  |    13.08        |
+  |wick.  | 12      |  1   5¼   | 3   27 | 41   24  |    13.92        |
+  |       | 10¾     |  1   8    | 3   36 | 38   24  |    15.00        |
+  |       |  7¾     |  2   1    | 4    9 | 32   12  |    17.88        |
+  |       |  8      |  2   0    | 4   15 | 34    0  |    16.94        |
+  |       |  5¾     |  2  13    | 5   19 | 30   15  |    19.06        |
+  |       |Mould    |           |        |          |Moulds at 14d.   |
+  |       |candles. |  Each.    |        |          | per dozen.      |
+  |With   |  3⅞     |  2  12    | 7   20 | 42   39  |    15.74        |
+  |wax’d  |  4      |  4   0    | 9    3 | 36   20  |    18.56        |
+  |wick.  |  3      |  5   2¾   |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 × 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
+13½_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                                  £ 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              £ 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        £ 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       £ 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 _naïveté_ 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 4¾ pecks of
+  coke and ½ 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 =
+17½lbs. 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. ½7 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 coloured
+_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° 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°
+  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 faggots 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   |        3½    to  5_d_      --       4¼
+  One Pound  |                                      ¼
+  -----------+------------------------------------------
+
+  -----------+-----------------------------------
+             |       _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     --    82½
+  One Peck   |   19½    to    21¼    --    20¼
+  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 --      71½
+  One Pound  |     3 to      4 --       3½
+  -----------+--------------------------------
+
+  -----------+-----------------------------------------
+             | }               |_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 1¼ to 1½
+  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 2½ inches deep, and has
+the spigot inserted 1½ 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 1½ 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.
+
+                                                            £.  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
+                                                         ---------
+                                                         £ 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._
+     ¼ inch in diameter                       0    4    a foot}
+     ⅜ ditto                                  0    4     ditto}
+     ½ ditto                                  0    5     ditto}
+     ⅝ ditto                                  0    6     ditto}
+     ¾ ditto                                  0    6½    ditto} in
+     ⅞ ditto                                       7     ditto} 15
+    1  inch, ditto                            0    7½    ditto} to
+    1¼ ditto                                  0    9     ditto} 18
+    1½ ditto                                  0   10½    ditto} feet
+    1¾ ditto                                  0   11     ditto} lengths.
+    2  inch, ditto                            1    1½    ditto}
+    2¼ ditto                                  1    4     ditto}
+    2½ ditto                                  1    5     ditto}
+    3 inch, ditto                             1    6½    ditto}
+    Copper pipes brazed ¼ inch                0    4    per foot
+    Ditto, ditto, ditto ⅜ inch                0    5½    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 £5  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}
+  ½ inch nuts, screws and washers to put iron pipes together 7d. per lb
+  ⅝ ditto                                                    7d. ditto
+  ¾ 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 Eidgenössische Technische Hochschule Zürich.
+
+Fractions like ½ 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 × 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
+
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+Project Gutenberg's A Practical Treatise on Gas-light, by Fredrick Accum
+
+This eBook is for the use of anyone anywhere at no cost and with
+almost no restrictions whatsoever.  You may copy it, give it away or
+re-use it under the terms of the Project Gutenberg License included
+with this eBook or online at www.gutenberg.org
+
+
+Title: 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.
+
+Author: Fredrick Accum
+
+Release Date: January 2, 2014 [EBook #44567]
+
+Language: English
+
+Character set encoding: ISO-8859-1
+
+*** START OF THIS PROJECT GUTENBERG EBOOK A PRACTICAL TREATISE ON GAS-LIGHT ***
+
+
+
+
+Produced by Chris Curnow, Harry Lam� and the Online
+Distributed Proofreading Team at http://www.pgdp.net (This
+file was produced from images generously made available
+by The Internet Archive)
+
+
+
+
+
+
+
+Transcriber's notes
+
+Italics in the original work are transcribed between _underscores_;
+small-capitals have been transcribed as all capitals. [::] represents
+the proportion symbol.
+
+More transcriber's notes and a list of corrections made may be found at
+the end of this text.
+
+
+[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 LINN�N SOCIETY, MEMBER
+  OF THE ROYAL ACADEMY OF SCIENCES OF BERLIN, &c. &c.
+
+  WITH SEVEN COLOURED 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_� : Q [::]
+  _b_� : (_b_� + Q)/_a_� = 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_� + Q)/_a_� (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� 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�, 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 � 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                                  � 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              � 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        � 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       � 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 _na�vet�_ 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 coloured
+_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� 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�
+  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 faggots 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.
+
+                                                            �.  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
+                                                         ---------
+                                                         � 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 �5  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 Eidgen�ssische Technische Hochschule Z�rich.
+
+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 � 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
+
+*** END OF THIS PROJECT GUTENBERG EBOOK A PRACTICAL TREATISE ON GAS-LIGHT ***
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+<pre>
+
+Project Gutenberg's A Practical Treatise on Gas-light, by Fredrick Accum
+
+This eBook is for the use of anyone anywhere at no cost and with
+almost no restrictions whatsoever.  You may copy it, give it away or
+re-use it under the terms of the Project Gutenberg License included
+with this eBook or online at www.gutenberg.org
+
+
+Title: 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.
+
+Author: Fredrick Accum
+
+Release Date: January 2, 2014 [EBook #44567]
+
+Language: English
+
+Character set encoding: ISO-8859-1
+
+*** START OF THIS PROJECT GUTENBERG EBOOK A PRACTICAL TREATISE ON GAS-LIGHT ***
+
+
+
+
+Produced by Chris Curnow, Harry Lam� and the Online
+Distributed Proofreading Team at http://www.pgdp.net (This
+file was produced from images generously made available
+by The Internet Archive)
+
+
+
+
+
+
+</pre>
+
+
+<div class="tnbox">
+<p class="center">Please see the <a href="#TN">Transcriber&#8217;s Notes</a> at the end of this text.</p>
+</div>
+
+<div class="figcenter"><a name="Plate1" id="Plate1"></a>
+<img src="images/illo001.jpg" alt="Gas plant" width="600" height="469" />
+<p class="largeimg"><a href="images/lg001.jpg">Larger image</a> (546 kB)</p>
+</div>
+
+<h1><span class="fsize40">A</span><br />
+<span class="fsize80">PRACTICAL TREATISE</span><br />
+<span class="fsize40">ON</span><br />
+<span class="fsize150"><b>GAS-LIGHT;</b></span><br />
+<span class="fsize40">EXHIBITING</span><br />
+<span class="fsize80">A SUMMARY DESCRIPTION</span><br />
+<span class="fsize40">OF THE</span><br />
+APPARATUS AND MACHINERY<br />
+<span class="fsize40">BEST CALCULATED FOR</span><br />
+<span class="gesp">ILLUMINATING</span><br />
+<span class="fsize80">STREETS, HOUSES, AND MANUFACTORIES,</span><br />
+<span class="fsize40">WITH</span><br />
+<span class="fsize80">CARBURETTED HYDROGEN, OR COAL-GAS,</span><br />
+WITH REMARKS<br />
+<span class="fsize40">ON THE</span><br />
+<span class="fsize60">UTILITY, SAFETY, AND GENERAL NATURE OF THIS NEW BRANCH<br />
+OF CIVIL ECONOMY.</span></h1>
+
+<hr class="sect" />
+
+<p class="center highline"><span class="fsize125"><span class="smcap">By</span> FREDRICK ACCUM,</span><br />
+<i>OPERATIVE CHEMIST</i>,<br />
+<span class="fsize80">LECTURER ON PRACTICAL CHEMISTRY, ON MINERALOGY, AND ON CHEMISTRY<br />
+APPLIED TO THE ARTS AND MANUFACTURES; MEMBER OF THE ROYAL<br />
+IRISH ACADEMY, FELLOW OF THE LINN&AElig;N SOCIETY, MEMBER<br />
+OF THE ROYAL ACADEMY OF SCIENCES OF BERLIN, &amp;c. &amp;c.</span></p>
+
+<hr class="sect" />
+
+<p class="center fsize125">WITH SEVEN COLOURED PLATES.</p>
+
+<hr class="sect" />
+
+<p class="center"><span class="oldtype fsize125">London:</span><br />
+<span class="fsize80">PRINTED BY G. HAYDEN, BRYDGES-STREET, COVENT GARDEN;<br />
+FOR R. ACKERMANN, 101, STRAND;<br />
+<i>LONGMAN, HURST, REES, ORME, AND BROWN; AND SHERWOOD, NEELY, AND<br />
+JONES, PATERNOSTER ROW; AND J. HATCHARD, PICCADILLY</i>.</span></p>
+
+<p class="center"><em class="italic">Price&mdash;Twelve Shillings in Boards.</em></p>
+
+<hr class="sect" />
+
+<p class="center">1815.</p>
+
+<hr class="chap" />
+
+<p class="motto center">EX FUMO DARE LUCEM.</p>
+
+<p class="motto right"><span class="smcap">Hor.</span></p>
+
+<hr class="chap" />
+
+<p><span class="pagenum"><a name="Page_i1" id="Page_i1">[i]</a></span></p>
+
+<h2>PREFACE.</h2>
+
+<p class="rightsig"><i>11, Compton Street Soho.</i></p>
+
+<p>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 <span class="smcap">Gas-Light</span>.</p>
+
+<p>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&mdash;I have explained the action of candles and
+lamps&mdash;I have shown the methods of measuring
+the comparative illuminating power of artificial
+light of different kinds, so as to appreciate their
+economical value&mdash;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.</p>
+
+<p>These positions are followed by a chemical view
+of the general nature and composition of coal&mdash;the
+chemical changes which this substance suffers, when
+employed in the production of gas-light&mdash;the different<span class="pagenum"><a name="Page_ii1" id="Page_ii1">[ii]</a></span>
+products it furnishes&mdash;the modes of obtaining
+them&mdash;their properties and applications in the various
+arts of life.</p>
+
+<p>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;&mdash;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&mdash;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.</p>
+
+<p>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.</p>
+
+<p>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&mdash;its views&mdash;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.</p>
+
+<p><span class="pagenum"><a name="Page_iii1" id="Page_iii1">[iii]</a></span></p>
+
+<p>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.</p>
+
+<p>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.</p>
+
+<p class="rightsig gesp blankabove">FREDRICK ACCUM</p>
+
+<hr class="chap" />
+
+<p><span class="pagenum"><a name="Page_i2" id="Page_i2">[i]</a></span></p>
+
+<h2 class="oldtype">Contents.</h2>
+
+<table class="toc" summary="ToC">
+
+<tr>
+<td class="secname"><b>INTRODUCTORY OBSERVATION.</b></td>
+<td class="pagenr">Page</td>
+<td class="pagenr"><a href="#Page_1">1.</a></td>
+</tr>
+
+<tr>
+<td colspan="3" class="just">Progress of the arts.&mdash;Influence of it upon the morals and condition
+of man.&mdash;Beneficial tendency of chemical and mechanical
+improvements.&mdash;State of pre-eminence of people with regard to
+civilization.&mdash;How to be estimated.&mdash;Flourishing state of those
+nations which have shown the greatest activity in cultivating the
+useful arts, and establishing useful enterprises.&mdash;General observations
+on this subject.&mdash;Extraordinary discoveries of modern
+times.&mdash;New art of procuring light.&mdash;Object of the treatise.</td>
+</tr>
+
+<tr>
+<td colspan="3" class="partnr">PART I.</td>
+</tr>
+
+<tr>
+<td colspan="2" class="secname"><b>PRODUCTION OF ARTIFICIAL LIGHT, &amp;c.</b></td>
+<td class="pagenr"><a href="#Page_8">8.</a></td>
+</tr>
+
+<tr>
+<td colspan="3" class="just">Production of the flame generated during the combustion of certain
+bodies.&mdash;Characters of flame when perfect.&mdash;Most luminous
+flame, how produced with the least consumption of combustible
+matter.&mdash;Conditions necessary for that purpose.&mdash;Importance of
+this subject, with regard to the production and supply of artificial
+light.&mdash;The flame of bodies may be tinged.&mdash;Blue flame,
+red flame, green flame, &amp;c.&mdash;Opinion concerning the origin of
+light emitted by bodies burning with flame.&mdash;Philosophy of
+the subject.&mdash;Theory of the action of the instruments of illumination.&mdash;Rude
+method of procuring light employed in some
+countries.&mdash;Chemical action of candles, and lamps.&mdash;Agency of
+the tallow, oil, &amp;c.&mdash;Office of the wick.&mdash;Reason why tallow
+candles require snuffing, and wax candles snuff themselves&mdash;Further
+observations on the subject.</td>
+</tr>
+
+<tr>
+<td colspan="2" class="secname"><b>METHOD OF ASCERTAINING THE ILLUMINATING
+POWER OF CANDLES, LAMPS, AND
+OTHER LUMINOUS BODIES.</b></td>
+<td class="pagenr"><a href="#Page_22">22.</a></td>
+</tr>
+
+<tr>
+<td colspan="3" class="just">Optical principle assumed as law for determining the relative
+strength of lights of different kinds.&mdash;Admeasurement of the
+intensities of light.&mdash;Quantity of wax, tallow, oil, &amp;c. requisite
+for producing a light of a certain strength.&mdash;Method of increasing
+the light of tallow candles, and to obviate the necessity of
+snuffing them.&mdash;A tallow candle placed in an inclined position
+gives more light than when placed perpendicularly and snuffed
+with an instrument.&mdash;Explanation of the fact.&mdash;Further observations
+on this subject.&mdash;Comparative cost of the light obtained by
+burning tallow candles of different sorts and sizes.</td>
+</tr>
+
+<tr>
+<td colspan="3" class="partnr">PART II.<span class="pagenum"><a name="Page_ii2" id="Page_ii2">[ii]</a></span></td>
+</tr>
+
+<tr>
+<td colspan="2" class="secname"><b>GAS-LIGHT.</b></td>
+<td class="pagenr"><a href="#Page_47">47.</a></td>
+</tr>
+
+<tr>
+<td colspan="3" class="just">Encouragement given by the legislature to the new system of procuring
+light.&mdash;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.&mdash;Power
+and authorities granted to this corporate body.&mdash;are
+very restricted, and do not prevent other individuals from
+entering into competition with them.&mdash;Boundaries of their experiments.&mdash;limit
+of capital employed by them.&mdash;Power of His
+Majesty with regard to the gas-light charter.</td>
+</tr>
+
+<tr>
+<td colspan="2" class="secname"><b>THEORY OF THE COMBUSTION OF COAL IN
+ELUCIDATION OF THE NATURE OF GAS-LIGHT.</b></td>
+<td class="right bot"><a href="#Page_49">49.</a></td>
+</tr>
+
+<tr>
+<td colspan="3" class="just">Natural history of pit-coal.&mdash;Immediate constituent parts of coal.&mdash;Their
+relative quantities&mdash;are different in different kinds of
+coal.&mdash;Phenomena, which happen during the combustion of
+coal.&mdash;Analysis of coal by distillation.&mdash;Great waste of matter
+capable of producing light and heat, in the usual mode of burning
+coal.&mdash;Proofs of this statement.&mdash;Theory of the production
+of gas-light, compared with the production of light obtained by
+candles and lamps.&mdash;Place which the discovery of lighting with
+gas occupies in the philosophical order of knowledge.</td>
+</tr>
+
+<tr>
+<td colspan="2" class="secname"><b>HISTORICAL SKETCH OF THE RISE AND PROGRESS
+OF THE APPLICATION OF COAL-GAS
+AS A SUBSTITUTE FOR PROCURING ARTIFICIAL
+LIGHT.</b></td>
+<td class="pagenr"><a href="#Page_55">55.</a></td>
+</tr>
+
+<tr>
+<td colspan="3" class="just">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.&mdash;Early notices of the inflammable property of
+the gas obtained by distilling coal.&mdash;Attempts to substitute it for
+tallow and oil.&mdash;Experiments made with coal-gas by Dr. <span class="smcap">Clayton</span>,
+Dr. <span class="smcap">Hales</span>, and the Bishop of Llandaff.&mdash;First successful
+attempt of lighting manufactories with gas.&mdash;<em class="italic">Creditor</em> and <em class="italic">debtor</em>
+account concerning the expence of this mode of illumination,
+when compared with the light obtained by tallow candles.&mdash;Claims
+of Mr. <span class="smcap">Murdoch</span> with regard to the economical application
+of coal-gas.&mdash;Claims of Mr. <span class="smcap">Winsor</span>.&mdash;Experiments
+of Mr. <span class="smcap">Northern</span>, Mr. <span class="smcap">Clegg</span>, Mr. <span class="smcap">Cook</span>, Mr. <span class="smcap">Ackermann</span>.&mdash;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.</td>
+</tr>
+
+<tr>
+<td colspan="2" class="secname"><b>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.</b><span class="pagenum"><a name="Page_iii2" id="Page_iii2">[iii]</a></span></td>
+<td class="pagenr"><a href="#Page_77">77.</a></td>
+</tr>
+
+<tr>
+<td colspan="3" class="just">Philosophy of the production of coal-gas.&mdash;Characters of the various
+products which the gas-light process affords, their quantities,
+and modes of obtaining them.&mdash;Quantity of gas obtainable from
+a given weight of coal.&mdash;Illuminating power of a given bulk of
+coal-gas compared with the illuminating power of a given weight
+of tallow candles.&mdash;Practical directions with regard to the production
+of the gas from coal.&mdash;Its chemical constitution and analysis.&mdash;Pit-coal
+is not the only substance which affords carburetted
+hidrogen gas.&mdash;This gas exists ready formed in nature.&mdash;Mode of
+collecting it when found native.&mdash;Is given out by all kinds of
+vegetable matter, submitted to distillation in close vessels.&mdash;Other
+sources of obtaining this gazeous fluid.&mdash;Practical directions
+with regard to the method of obtaining from coal, this gazeous
+substance, as best suited for illumination.&mdash;Chemical constitution
+of coal-gas.&mdash;How ascertained.</td>
+</tr>
+
+<tr>
+<td colspan="2" class="secname"><b>UTILITY OF THE GAS-LIGHT ILLUMINATION
+WITH REGARD TO PUBLIC AND PRIVATE
+ECONOMY.</b></td>
+<td class="pagenr"><a href="#Page_99">99.</a></td>
+</tr>
+
+<tr>
+<td colspan="3" class="just">Objects to which the new system of lighting with gas may be beneficially
+applied.&mdash;Capital advantages of the gas-light illumination.&mdash;Places
+and public edifices lighted with coal-gas in this metropolis.&mdash;Situations
+best suited for the application of gas-lights.&mdash;places
+where it cannot be used to advantage.&mdash;Illumination of
+barracks, arsenals, dock yards, &amp;c. with coal-gas.&mdash;Further observations
+on this subject.&mdash;Great heat produced by gas-lights.&mdash;Reason
+why the flame of coal-gas produces more heat than the
+flame of candles and lamps.&mdash;Admeasurement of the comparative
+degrees of heat produced by gas-lights, oil lamps, tallow
+and wax candles, &amp;c.&mdash;Gas lamps and burners, various kinds
+of.&mdash;Ornamental chandeliers and candelabras, for applying coal-gas
+as a substitute for oil.&mdash;Other products obtainable from coal
+besides gas.&mdash;<em class="italic">Coke.</em>&mdash;Its nature.&mdash;Combustion of it.&mdash;Produces
+a more strong and lasting heat than coal.&mdash;Explanation of this
+fact.&mdash;Advantages resulting from the use of coke as fuel.&mdash;Disadvantages
+of its application in certain circumstances.&mdash;Relative
+effect of heat produced by equal quantities of coke and charcoal.&mdash;Method
+of measuring the comparative effect of different kinds
+of fuel in producing heat.&mdash;Capital advantages resulting from
+the application of coke, as fuel, in the art of burning lime.&mdash;Plaster
+of Paris, bricks, &amp;c.&mdash;Quantity of coke obtainable from
+<span class="pagenum"><a name="Page_iv2" id="Page_iv2">[iv]</a></span>a certain quantity of pit-coal.&mdash;Kind of coke best suited for
+metallurgical operations.&mdash;Mode of obtaining it in the gas-light
+process.&mdash;Sort of coke best adapted for kitchen and parlour fires.&mdash;Manufacture
+of it.&mdash;<em class="italic">Coal tar.</em>&mdash;How obtained.&mdash;Its properties.&mdash;Earl
+of Dundonald&#8217;s method of manufacturing tar from coal.&mdash;Quantity
+of coal-tar produced in the gas-light process from a
+given quantity of coal.&mdash;Characters of coal tar obtained from
+Newcastle coal, differ from that produced from canel coal.&mdash;<em class="italic">Coal
+pitch.</em>&mdash;Process for obtaining it.&mdash;Properties of coal-pitch.&mdash;Use
+of it in the arts.&mdash;quantity of coal-pitch obtainable from a
+given quantity of tar.&mdash;<em class="italic">Ammoniacal liquor</em> produced during the
+distillation of coal.&mdash;Its chemical constitution.&mdash;Quantity obtained
+from a given quantity of coal.&mdash;General observation
+respecting the scheme of applying coal-gas as a substitute for
+candles and lamps.&mdash;Effects which it must produce upon the arts
+and upon domestic economy.&mdash;Its views.&mdash;Primary advantages.&mdash;Resources
+which it presents to industry and public economy.&mdash;In
+what respect it is entitled to public approbation and national
+encouragement.&mdash;Effects of prejudice against the introduction
+of new and useful discoveries.&mdash;Have operated strongly in retarding
+the gas-light illumination.&mdash;Remarkable slowness with
+which improvements of extended utility make their way into
+common use, contrasted with the rapid adoption of fashionable
+changes.&mdash;Other causes unfavourable to the adoption of new and
+useful plans.&mdash;Further observations on this subject.&mdash;The new
+system of lighting with coal-gas can never supersede the use of
+candles and moveable lights.&mdash;Gas-light illumination cannot
+prove injurious to the Greenland fishery&mdash;nor can it diminish
+the coal trade&mdash;must prove beneficial to it.&mdash;The price of coal
+even when it is the highest cannot materially affect the beneficial
+application of gas-lights.&mdash;Striking advantages to be derived
+from the introduction of gas-lights into manufactories.&mdash;Principal
+expense which must always attend the gas-light illumination.&mdash;Is
+the dead capital employed for erecting the machinery.&mdash;Floating
+capital is small.&mdash;Advice to private individuals with
+regard to the erection of a gas-light apparatus calculated for their
+own use.&mdash;Expence which must attend the application of the
+new system of lighting under different circumstances.&mdash;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.&mdash;Management of the gas-light machinery
+is extremely simple and easy.&mdash;The apparatus not liable
+to be out of order.&mdash;Observations on the safety of the gas-light
+illumination.&mdash;Misapprehension of the public concerning it.&mdash;Causes
+that have alarmed the public concerning the application
+of the new lights.&mdash;Gas-lights cannot give rise to those accidents
+which have so often arisen from the careless snuffing of candles,
+<span class="pagenum"><a name="Page_v2" id="Page_v2">[v]</a></span>&amp;c.&mdash;Produce no embers or sparks.&mdash;Cannot fall, or be disturbed
+without becoming extinguished.&mdash;Are the safest of all
+lights.&mdash;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&mdash;or by the destruction of one or
+more of the gas-light machineries employed for preparing the
+gas.&mdash;Illustration showing the absurdity of such mistaken notions.&mdash;Curious
+self-extinguishing lamp, invented by Mr. <span class="smcap">Clegg</span>.&mdash;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 <em class="italic">main</em>.&mdash;Leading characters of the new lights.&mdash;Objects
+and views which this art embraces.&mdash;It must lessen the
+consumption of oil.&mdash;Occasion a defalcation in the revenue.</td>
+</tr>
+
+<tr>
+<td colspan="2" class="secname"><b>TABULAR VIEW</b>, Exhibiting the quantity of <span class="smcap">Gas</span>, <span class="smcap">Coke</span>,
+<span class="smcap">Tar</span>, <span class="smcap">Pitch</span>, <span class="smcap">Essential Oil</span>, and <span class="smcap">Ammoniacal Liquor</span>, obtainable
+from a given quantity of <span class="smcap">Coal</span>: 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.</td>
+<td class="pagenr"><a href="#Page_164">164.</a></td>
+</tr>
+
+<tr>
+<td colspan="2" class="secname"><b>DESCRIPTION OF THE GAS-LIGHT APPARATUS.</b></td>
+<td class="pagenr"><a href="#Page_166">166.</a></td>
+</tr>
+
+<tr>
+<td colspan="2" class="secname"><b>METHOD</b> of correcting the relative pressure of the Gasometer,
+so as to cause the gas which it contains to be uniformly of an
+equal density.</td>
+<td class="pagenr"><a href="#Page_181">181.</a></td>
+</tr>
+
+<tr>
+<td colspan="2" class="secname"><b>DIRECTIONS TO WORKMEN ATTENDING THE
+GAS-LIGHT APPARATUS.</b></td>
+<td class="pagenr"><a href="#Page_182">182.</a></td>
+</tr>
+
+<tr>
+<td colspan="2" class="secname"><b>ESTIMATE</b> of the price of a Gas-Light Apparatus.</td>
+<td class="pagenr"><a href="#Page_185">185.</a></td>
+</tr>
+
+<tr>
+<td colspan="2" class="secname"><b>LONDON</b> Price List of the most essential articles employed in
+the erection of a Gas-light Apparatus.</td>
+<td class="pagenr"><a href="#Page_186">186.</a></td>
+</tr>
+
+</table>
+
+<hr class="sect" />
+
+<h2 class="small">ERRATA.</h2>
+
+<table class="fsize80" summary="Errata">
+
+<tr>
+<td class="left top padr1">Page</td>
+<td class="right top">24,</td>
+<td class="left top padl1 padr1">line</td>
+<td class="right top">11,</td>
+<td class="left top padl1"><em class="italic">for</em> too, <em class="italic">read</em> two.</td>
+</tr>
+
+<tr>
+<td>&nbsp;</td>
+<td class="right top">48,</td>
+<td>&nbsp;</td>
+<td class="right top">22,</td>
+<td class="left top padl1"><em class="italic">for</em> corporated, <em class="italic">read</em> incorporated.</td>
+</tr>
+
+<tr>
+<td>&nbsp;</td>
+<td class="right top">53,</td>
+<td>&nbsp;</td>
+<td class="right top">7,</td>
+<td class="left top padl1"><em class="italic">for</em> this combustion, <em class="italic">read</em> the combustion.</td>
+</tr>
+
+<tr>
+<td>&nbsp;</td>
+<td class="right top">64,</td>
+<td>&nbsp;</td>
+<td class="right top">24,</td>
+<td class="left top padl1"><em class="italic">for</em> <span class="smcap">Cleg</span>, <em class="italic">read</em> <span class="smcap">Clegg</span>.</td>
+</tr>
+
+<tr>
+<td>&nbsp;</td>
+<td class="right top"><em class="italic">ibid</em></td>
+<td>&nbsp;</td>
+<td class="right top">25,</td>
+<td class="left top padl1"><em class="italic">for</em> communicates, <em class="italic">read</em> communicated.</td>
+</tr>
+
+<tr>
+<td>&nbsp;</td>
+<td class="right top">65,</td>
+<td colspan="2">&nbsp;</td>
+<td class="left top padl1">erase the * and put it after the word <span class="smcap">Clegg</span>, line 24, p. 64.</td>
+</tr>
+
+<tr>
+<td>&nbsp;</td>
+<td class="right top"><em class="italic">ibid</em></td>
+<td>&nbsp;</td>
+<td class="right top">17,</td>
+<td class="left top padl1"><em class="italic">for</em> attemps, <em class="italic">read</em> attempts.</td>
+</tr>
+
+<tr>
+<td>&nbsp;</td>
+<td class="right top">125,</td>
+<td>&nbsp;</td>
+<td class="right top">23,</td>
+<td class="left top padl1"><em class="italic">for</em> degree, <em class="italic">read</em> degrees.</td>
+</tr>
+
+<tr>
+<td>&nbsp;</td>
+<td class="right top">132,</td>
+<td>&nbsp;</td>
+<td class="right top">25,</td>
+<td class="left top padl1"><em class="italic">for</em> coal, <em class="italic">read</em> coal-tar.</td>
+</tr>
+
+</table>
+
+<hr class="sect" />
+
+<h2 class="small">DIRECTIONS TO THE BINDER:</h2>
+
+<p class="fsize80"><a href="#Plate1">Plate I.</a> facing the title; <a href="#Plate2">plate II.</a> facing page 79; <a href="#Plate3">plate III.</a> facing page 115;
+<a href="#Plate4">plate IV.</a> facing page 119; <a href="#Plate5">plate V.</a> facing page 120; and <a href="#Plate6">plates VI.</a>
+and <a href="#Plate7">VII.</a> at the end of the book.</p>
+
+<hr class="chap" />
+
+<p><span class="pagenum"><a name="Page_1" id="Page_1">[1]</a></span></p>
+
+<p class="pseudoh1">A<br />
+<span class="fsize150">PRACTICAL TREATISE</span><br />
+ON<br />
+<span class="fsize175">GAS-LIGHT.</span></p>
+
+<hr class="chap" />
+
+<h2>INTRODUCTORY OBSERVATION.</h2>
+
+<hr class="sect" />
+
+<h3>INFLUENCE<br />
+<span class="fsize60">OF</span><br />
+THE PROGRESS OF THE ARTS<br />
+<span class="fsize60">UPON THE</span><br />
+MORALS AND CONDITION OF MAN.</h3>
+
+<p class="largecap">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<span class="pagenum"><a name="Page_2" id="Page_2">[2]</a></span>
+civilization is, and ought ever to be, estimated
+by the proportional state of industry, and useful
+labour existing among them.</p>
+
+<p>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 <span class="smcap">Smith</span><a name="FNanchor_1" id="FNanchor_1"></a><a href="#Footnote_1" class="fnanchor">[1]</a>
+emphatically remarks, that &#8220;the accommodation
+of an European prince does not
+always so much exceed that of an industrious<span class="pagenum"><a name="Page_3" id="Page_3">[3]</a></span>
+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.&#8221;</p>
+
+<div class="footnote">
+
+<p><a name="Footnote_1" id="Footnote_1"></a><a href="#FNanchor_1"><span class="label">[1]</span></a> Wealth of Nations, chap. 1.</p></div>
+
+<p>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.</p>
+
+<p>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<span class="pagenum"><a name="Page_4" id="Page_4">[4]</a></span>
+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.</p>
+
+<p>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?&mdash;or
+imagined the astonishing effect of gun-powder&mdash;or
+the extended application of the steam
+engine? What mortal would have dared to
+dive to the bottom of the sea&mdash;or to soar aloft
+into the air&mdash;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<span class="pagenum"><a name="Page_5" id="Page_5">[5]</a></span>
+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.</p>
+
+<p>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.</p>
+
+<p>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&mdash;whether he might store
+the fruits of the earth for his winter supply&mdash;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<span class="pagenum"><a name="Page_6" id="Page_6">[6]</a></span>
+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.</p>
+
+<p>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.</p>
+
+<p><span class="pagenum"><a name="Page_7" id="Page_7">[7]</a></span></p>
+
+<p>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.</p>
+
+<p>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.</p>
+
+<hr class="chap" />
+
+<p><span class="pagenum"><a name="Page_8" id="Page_8">[8]</a></span></p>
+
+<h2>PART I.</h2>
+
+<hr class="chap" />
+
+<h3>PRODUCTION<br />
+<span class="fsize60">OF</span><br />
+ARTIFICIAL LIGHT;<br />
+<span class="fsize60">AND</span><br />
+<span class="gesp">THEORY</span><br />
+<span class="fsize60">OF THE</span><br />
+ACTION OF CANDLES AND LAMPS.</h3>
+
+<p>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<span class="pagenum"><a name="Page_9" id="Page_9">[9]</a></span>
+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&mdash;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.</p>
+
+<p>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<span class="pagenum"><a name="Page_10" id="Page_10">[10]</a></span>
+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.</p>
+
+<p>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,<span class="pagenum"><a name="Page_11" id="Page_11">[11]</a></span>
+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.</p>
+
+<p>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.</p>
+
+<p>That in many cases the light evolved by artificial
+means is derived from the combustible<span class="pagenum"><a name="Page_12" id="Page_12">[12]</a></span>
+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.</p>
+
+<p>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.</p>
+
+<p>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.</p>
+
+<p>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<span class="pagenum"><a name="Page_13" id="Page_13">[13]</a></span>
+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.<a name="FNanchor_2" id="FNanchor_2"></a><a href="#Footnote_2" class="fnanchor">[2]</a></p>
+
+<div class="footnote">
+
+<p><a name="Footnote_2" id="Footnote_2"></a><a href="#FNanchor_2"><span class="label">[2]</span></a> See Chemical Amusement, comprising minute instructions
+for performing a series of striking and interesting
+chemical experiments, p. 8, &amp;c.</p></div>
+
+<p>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<span class="pagenum"><a name="Page_14" id="Page_14">[14]</a></span>
+the new system of illumination which it is the
+object of this Essay to explain.</p>
+
+<p>To procure light for the ordinary purposes
+of life, we are acquainted with no other ready
+means than the process of combustion.</p>
+
+<p>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.</p>
+
+<p>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.</p>
+
+<p>All these substances must be rendered volatile
+before they can produce a flame, but for
+this purpose it is sufficient to volatilize a small<span class="pagenum"><a name="Page_15" id="Page_15">[15]</a></span>
+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 <em class="italic">wick</em>,
+which in fact is the fire-place, or laboratory
+where the whole operation is conducted.</p>
+
+<p>There are three articles which demand our
+attention in the lamp&mdash;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.</p>
+
+<p>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<span class="pagenum"><a name="Page_16" id="Page_16">[16]</a></span>
+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,<span class="pagenum"><a name="Page_17" id="Page_17">[17]</a></span>
+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&#8217; shops, or with
+those of the lamp-lighters, the smoke is very
+offensive, and in great measure eclipses the
+light of the flame.</p>
+
+<p>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<span class="pagenum"><a name="Page_18" id="Page_18">[18]</a></span>
+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<span class="pagenum"><a name="Page_19" id="Page_19">[19]</a></span>
+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<span class="pagenum"><a name="Page_20" id="Page_20">[20]</a></span>
+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<span class="pagenum"><a name="Page_21" id="Page_21">[21]</a></span>
+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.
+<span class="smcap">Nicholson</span><a name="FNanchor_3" id="FNanchor_3"></a><a href="#Footnote_3" class="fnanchor">[3]</a> 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.</p>
+
+<div class="footnote">
+
+<p><a name="Footnote_3" id="Footnote_3"></a><a href="#FNanchor_3"><span class="label">[3]</span></a> Philosophical Journal, 4to Series, Vol. I. p. 70.</p>
+
+</div>
+
+<hr class="sect" />
+
+<p><span class="pagenum"><a name="Page_22" id="Page_22">[22]</a></span></p>
+
+<h3>METHOD<br />
+<span class="fsize60">OF</span><br />
+ASCERTAINING THE ILLUMINATING POWER<br />
+<span class="fsize60">OF</span><br />
+CANDLES, LAMPS, GAS-LIGHTS,<br />
+<span class="fsize60">AND</span><br />
+OTHER LUMINOUS BODIES.</h3>
+
+<p>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.</p>
+
+<p>For this purpose it is assumed as a principle,
+that the same quantity of light, diverging in<span class="pagenum"><a name="Page_23" id="Page_23">[23]</a></span>
+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.</p>
+
+<p>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<span class="pagenum"><a name="Page_24" id="Page_24">[24]</a></span>
+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;</p>
+
+<div class="figcenter">
+<img src="images/illo037.png" alt="Overlapping shadows" width="200" height="133" />
+</div>
+
+<p><span class="pagenum"><a name="Page_25" id="Page_25">[25]</a></span></p>
+
+<p>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<span class="pagenum"><a name="Page_26" id="Page_26">[26]</a></span>
+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:&mdash;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.</p>
+
+<p>From experiments made by Count <span class="smcap">Rumford</span>,
+concerning the quantity of materials requisite
+for producing a light of a certain intensity for<span class="pagenum"><a name="Page_27" id="Page_27">[27]</a></span>
+a given time: it was found that we must burn
+of wax 100, of tallow 101, of oil, in an Argand&#8217;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.<a name="FNanchor_4" id="FNanchor_4"></a><a href="#Footnote_4" class="fnanchor">[4]</a></p>
+
+<div class="footnote">
+
+<p><a name="Footnote_4" id="Footnote_4"></a><a href="#FNanchor_4"><span class="label">[4]</span></a> 112lbs. of Newcastle coal, called Tanfield Moor, produce,
+upon an average, from 250 to 300 cubic feet of gas,
+fit for illumination.</p></div>
+
+<hr class="sect" />
+
+<h4>FURTHER ILLUSTRATIONS<br />
+<span class="fsize60">OF THE</span><br />
+<span class="fsize60">MODE OF COMPUTING THE RELATIVE COST OR VALUE</span><br />
+<span class="fsize60">OF</span><br />
+LIGHT,<br />
+<span class="fsize60">EMITTED BY MEANS OF</span><br />
+CANDLES, LAMPS, &amp; OTHER BODIES.</h4>
+
+<p>It is sufficiently known that the light of a
+candle, which is so exceedingly brilliant when
+first snuffed, is very speedily diminished to<span class="pagenum"><a name="Page_28" id="Page_28">[28]</a></span>
+one-half and is usually not more than one-fifth
+or one-sixth before the uneasiness of the eye
+induces us to snuff it.<a name="FNanchor_5" id="FNanchor_5"></a><a href="#Footnote_5" class="fnanchor">[5]</a> 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.</p>
+
+<div class="footnote">
+
+<p><a name="Footnote_5" id="Footnote_5"></a><a href="#FNanchor_5"><span class="label">[5]</span></a> Ezekiel Walker.&mdash;Nicholson&#8217;s Journal, Vol. IV. 8vo.
+Series.</p></div>
+
+<p>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.</p>
+
+<p>To prove the truth of this position, Mr.
+Walker made the experiments contained in
+the following</p>
+
+<p><span class="pagenum"><a name="Page_29" id="Page_29">[29]</a></span></p>
+
+<p class="center">TABLE.</p>
+
+<table class="nowrap" summary="Table page 29">
+
+<tr class="bt bb">
+<th colspan="4" class="center padl1 padr1 bl br">No. of<br />the<br />Experi-<br />ment.</th>
+<th class="center padl1 padr1 br">No. of the<br />Candles.</th>
+<th colspan="2" class="center padl1 padr1 br">Time of<br />burning.</th>
+<th colspan="3" class="center padl1 padr1 br">Weight<br />of the<br />Candles<br />consumed<br />in a given<br />time.</th>
+<th colspan="2" class="center padl1 padr1 br">Strength<br />of Light.</th>
+<th colspan="2" class="center padl1 padr1 br">Distance<br />of the<br />Candles<br />from the<br />Wall.</th>
+</tr>
+
+<tr>
+<th colspan="4" class="bl br">&nbsp;</th>
+<th class="br">&nbsp;</th>
+<th class="center padl1 padr1">h.</th>
+<th class="br">&nbsp;</th>
+<th class="center padl1 padr1">oz.</th>
+<th colspan="2" class="center padl1 padr1 br">dr.</th>
+<th colspan="2" class="br">&nbsp;</th>
+<th colspan="2" class="center padl1 padr1 br">Feet.</th>
+</tr>
+
+<tr>
+<td rowspan="3" class="right padl1 padr1 bl">1</td>
+<td rowspan="3" class="right padr0 narrow">-</td>
+<td rowspan="3" class="bt bb bl narrow">&nbsp;</td>
+<td rowspan="3" class="br narrow">&nbsp;</td>
+<td class="center padl1 padr1 br">1</td>
+<td class="center padl1 padr1">3</td>
+<td class="right padl1 padr1 br">0</td>
+<td class="center padl1 padr1">0</td>
+<td class="right padl1 padr0">15</td>
+<td class="br">&nbsp;</td>
+<td class="right padl1 padr0">1</td>
+<td class="br">&nbsp;</td>
+<td class="right padl1 padr0">7</td>
+<td class="br">&nbsp;</td>
+</tr>
+
+<tr>
+<td class="center padl1 padr1 br">3</td>
+<td class="center padl1 padr1">3</td>
+<td class="right padl1 padr1 br">0</td>
+<td class="center padl1 padr1">1</td>
+<td class="right padl1 padr0">1</td>
+<td class="left padl0 padr1 br"><sup>1</sup>&#8260;<sub>2</sub></td>
+<td class="right padl1 padr0">1</td>
+<td class="center padl1 padr1 br">+</td>
+<td class="right padl1 padr0">7</td>
+<td class="br">&nbsp;</td>
+</tr>
+
+<tr>
+<td class="center padl1 padr1 br">Mould</td>
+<td class="center padl1 padr1">3</td>
+<td class="right padl1 padr1 br">0</td>
+<td class="center padl1 padr1">0</td>
+<td class="right padl1 padr0">15</td>
+<td class="br">&nbsp;</td>
+<td class="right padl1 padr0">1</td>
+<td class="br">&nbsp;</td>
+<td class="right padl1 padr0">7</td>
+<td class="br">&nbsp;</td>
+</tr>
+
+<tr class="thinrow bb">
+<td colspan="4" class="bl br">&nbsp;</td>
+<td class="br">&nbsp;</td>
+<td colspan="2" class="br">&nbsp;</td>
+<td colspan="3" class="br">&nbsp;</td>
+<td colspan="2" class="br">&nbsp;</td>
+<td colspan="2" class="br">&nbsp;</td>
+</tr>
+
+<tr class="thinrow">
+<td colspan="4" class="bl br">&nbsp;</td>
+<td class="br">&nbsp;</td>
+<td colspan="2" class="br">&nbsp;</td>
+<td colspan="3" class="br">&nbsp;</td>
+<td colspan="2" class="br">&nbsp;</td>
+<td colspan="2" class="br">&nbsp;</td>
+</tr>
+
+<tr>
+<td rowspan="3" class="right padl1 padr1 bl">2</td>
+<td rowspan="3" class="right padr0">-</td>
+<td rowspan="3" class="bt bb bl">&nbsp;</td>
+<td rowspan="3" class="br">&nbsp;</td>
+<td class="center padl1 padr1 br">1</td>
+<td class="center padl1 padr1">2</td>
+<td class="right padl1 padr1 br">55</td>
+<td class="center padl1 padr1">0</td>
+<td class="right padl1 padr0">15</td>
+<td class="br">&nbsp;</td>
+<td class="right padl1 padr0">1</td>
+<td class="br">&nbsp;</td>
+<td class="right padl1 padr0">8</td>
+<td class="br">&nbsp;</td>
+</tr>
+
+<tr>
+<td class="center padl1 padr1 br">3</td>
+<td class="center padl1 padr1">2</td>
+<td class="right padl1 padr1 br">55</td>
+<td class="center padl1 padr1">1</td>
+<td class="right padl1 padr0">0</td>
+<td class="br">&nbsp;</td>
+<td class="right padl1 padr0">1</td>
+<td class="center padl1 padr1 br">+</td>
+<td class="right padl1 padr0">8</td>
+<td class="br">&nbsp;</td>
+</tr>
+
+<tr>
+<td class="center padl1 padr1 br">Mould</td>
+<td class="center padl1 padr1">2</td>
+<td class="right padl1 padr1 br">55</td>
+<td class="center padl1 padr1">0</td>
+<td class="right padl1 padr0">15</td>
+<td class="br">&nbsp;</td>
+<td class="right padl1 padr0">1</td>
+<td class="br">&nbsp;</td>
+<td class="right padl1 padr0">8</td>
+<td class="br">&nbsp;</td>
+</tr>
+
+<tr class="thinrow bb">
+<td colspan="4" class="bl br">&nbsp;</td>
+<td class="br">&nbsp;</td>
+<td colspan="2" class="br">&nbsp;</td>
+<td colspan="3" class="br">&nbsp;</td>
+<td colspan="2" class="br">&nbsp;</td>
+<td colspan="2" class="br">&nbsp;</td>
+</tr>
+
+<tr class="thinrow">
+<td colspan="4" class="bl br">&nbsp;</td>
+<td class="br">&nbsp;</td>
+<td colspan="2" class="br">&nbsp;</td>
+<td colspan="3" class="br">&nbsp;</td>
+<td colspan="2" class="br">&nbsp;</td>
+<td colspan="2" class="br">&nbsp;</td>
+</tr>
+
+<tr>
+<td rowspan="3" class="right padl1 padr1 bl">3</td>
+<td rowspan="3" class="right padr0">-</td>
+<td rowspan="3" class="bt bb bl">&nbsp;</td>
+<td rowspan="3" class="br">&nbsp;</td>
+<td class="center padl1 padr1 br">1</td>
+<td class="center padl1 padr1">3</td>
+<td class="right padl1 padr1 br">0</td>
+<td class="center padl1 padr1">0</td>
+<td class="right padl1 padr0">15</td>
+<td class="left padl0 padr1 br"><sup>3</sup>&#8260;<sub>4</sub></td>
+<td class="right padl1 padr0">1</td>
+<td class="br">&nbsp;</td>
+<td class="right padl1 padr0">8</td>
+<td class="br">&nbsp;</td>
+</tr>
+
+<tr>
+<td class="center padl1 padr1 br">3</td>
+<td class="center padl1 padr1">3</td>
+<td class="right padl1 padr1 br">0</td>
+<td class="center padl1 padr1">1</td>
+<td class="right padl1 padr0">2</td>
+<td class="br">&nbsp;</td>
+<td class="right padl1 padr0">1</td>
+<td class="left padl0 padr1 br"><sup>1</sup>&#8260;<sub>8</sub></td>
+<td class="right padl1 padr0">8</td>
+<td class="left padl0 padr1 br"><sup>3</sup>&#8260;<sub>4</sub></td>
+</tr>
+
+<tr>
+<td class="center padl1 padr1 br">Mould</td>
+<td class="center padl1 padr1">3</td>
+<td class="right padl1 padr1 br">0</td>
+<td class="center padl1 padr1">0</td>
+<td class="right padl1 padr0">0</td>
+<td class="br">&nbsp;</td>
+<td class="right padl1 padr0">1</td>
+<td class="br">&nbsp;</td>
+<td class="right padl1 padr0">9</td>
+<td class="br">&nbsp;</td>
+</tr>
+
+<tr class="thinrow bb">
+<td colspan="4" class="bl br">&nbsp;</td>
+<td class="br">&nbsp;</td>
+<td colspan="2" class="br">&nbsp;</td>
+<td colspan="3" class="br">&nbsp;</td>
+<td colspan="2" class="br">&nbsp;</td>
+<td colspan="2" class="br">&nbsp;</td>
+</tr>
+
+<tr class="thinrow">
+<td colspan="4" class="bl br">&nbsp;</td>
+<td class="br">&nbsp;</td>
+<td colspan="2" class="br">&nbsp;</td>
+<td colspan="3" class="br">&nbsp;</td>
+<td colspan="2" class="br">&nbsp;</td>
+<td colspan="2" class="br">&nbsp;</td>
+</tr>
+
+<tr>
+<td rowspan="2" class="right padl1 padr1 bl">4</td>
+<td rowspan="2" class="right padr0">-</td>
+<td rowspan="2" class="bt bb bl">&nbsp;</td>
+<td rowspan="2" class="br">&nbsp;</td>
+<td class="center padl1 padr1 br">5</td>
+<td class="center padl1 padr1">3</td>
+<td class="right padl1 padr1 br">0</td>
+<td class="center padl1 padr1">1</td>
+<td class="right padl1 padr0">5</td>
+<td class="br">&nbsp;</td>
+<td class="right padl1 padr0">1</td>
+<td class="left padl0 padr1 br">.18</td>
+<td class="right padl1 padr0">8</td>
+<td class="left padl0 padr1 br"><sup>3</sup>&#8260;<sub>4</sub></td>
+</tr>
+
+<tr>
+<td class="center padl1 padr1 br">Mould</td>
+<td class="center padl1 padr1">3</td>
+<td class="right padl1 padr1 br">0</td>
+<td class="center padl1 padr1">1</td>
+<td class="right padl1 padr0">1</td>
+<td class="left padl0 padr1 br"><sup>1</sup>&#8260;<sub>8</sub></td>
+<td class="right padl1 padr0">1</td>
+<td class="left padl0 padr1 br">.</td>
+<td class="right padl1 padr0">8</td>
+<td class="br">&nbsp;</td>
+</tr>
+
+<tr class="thinrow bb">
+<td colspan="4" class="bl br">&nbsp;</td>
+<td class="br">&nbsp;</td>
+<td colspan="2" class="br">&nbsp;</td>
+<td colspan="3" class="br">&nbsp;</td>
+<td colspan="2" class="br">&nbsp;</td>
+<td colspan="2" class="br">&nbsp;</td>
+</tr>
+
+</table>
+
+<p>These experiments, Mr. Walker informs us,
+were made in the following manner:&mdash;</p>
+
+<p>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,<span class="pagenum"><a name="Page_30" id="Page_30">[30]</a></span>
+and the loss of weight of each candle is contained
+in the fourth column.</p>
+
+<p>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&#8217;s
+mind could not be under the influence
+of partiality for a system.</p>
+
+<p>The method which Mr. Walker employed
+in comparing one light with another in each
+experiment, was that which has been described
+<a href="#Page_24">page 24</a>.</p>
+
+<p>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.</p>
+
+<p>2. The sign + in the 5th column, signifies<span class="pagenum"><a name="Page_31" id="Page_31">[31]</a></span>
+that the candle against which it is placed, gave
+a stronger light than the others.</p>
+
+<p>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.</p>
+
+<p>For if their quantities of matter be equal,
+and times of burning the same, they will give
+equal quantities of light, <em class="italic">by the experiments</em>.</p>
+
+<p>And if the times of burning be equal, the
+quantities of light will be directly as their
+weights of matter expended.</p>
+
+<p>Therefore the light is universally in the
+compound ratio of the time of burning and
+weight of matter consumed.</p>
+
+<p>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.</p>
+
+<p>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<span class="pagenum"><a name="Page_32" id="Page_32">[32]</a></span>
+of light produced under these circumstances,
+be represented by 1.00.</p>
+
+<p>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.<a name="FNanchor_6" id="FNanchor_6"></a><a href="#Footnote_6" class="fnanchor">[6]</a></p>
+
+<div class="footnote">
+
+<p><a name="Footnote_6" id="Footnote_6"></a><a href="#FNanchor_6"><span class="label">[6]</span></a> To investigate rules for this purpose, 1. Let M represent
+the mould candle, <i>a</i> its distance from the wall, on
+which the shadows were compared, <i>x</i> its quantity of matter
+consumed in a given time, (<i>t</i>) and Q the quantity of light
+emitted by M in the same time: 2. Let <i>m</i> represent any
+other candle, <i>b</i> its distance from the same wall, and <i>y</i> its
+quantity of matter consumed, in the time <i>t</i>.</p>
+
+<p>Then as the intensities of light are directly as the squares
+of the distances of the two candles from the wall, we have as
+<i>a</i><sup>2</sup>&nbsp;: Q&nbsp;<span class="symbol">&#8759;</span><span class="symbol_e">::</span> <i>b</i><sup>2</sup>&nbsp;:
+<span class="division"><span class="num"><i>b</i><sup class="division">2</sup> + Q</span><span class="denom"><i>a</i><sup class="division">2</sup></span></span> = the quantity of light, emitted by
+<i>m</i> in the time.</p>
+
+<p>Then let us suppose that the quantities of light are directly
+as the quantities of matter consumed in the time <i>t</i>, and we
+have, As <i>x</i>&nbsp;: Q&nbsp;<span class="symbol">&#8759;</span><span class="symbol_e">::</span> <i>y</i>&nbsp;: <span class="division"><span class="num"><i>y</i> + Q</span><span class="denom"><i>x</i></span></span> = the quantity of light emitted
+by <i>m</i> in that time, by hypothesis.</p>
+
+<p>Now, when <span class="division"><span class="num"><i>b</i><sup class="division">2</sup> + Q</span><span class="denom"><i>a</i><sup class="division">2</sup></span></span> (Theo. 1.) is = <span class="division"><span class="num">Y + Q</span><span class="denom">X</span></span> (Theo. 2.) the
+quantities of light of M and <i>m</i> are directly as their quantities
+of matter consumed in any given time.</p>
+
+</div>
+
+<hr class="sect" />
+
+<p><span class="pagenum"><a name="Page_33" id="Page_33">[33]</a></span></p>
+
+<h4>METHOD<br />
+<span class="fsize60">OF INCREASING</span><br />
+THE LIGHT OF TALLOW CANDLES,<br />
+<span class="fsize60">AND TO OBVIATE THE</span><br />
+NECESSITY OF SNUFFING THEM.</h4>
+
+<p>Mr. <span class="smcap">Ezekiel Walker</span> 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.</p>
+
+<p>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<a name="FNanchor_7" id="FNanchor_7"></a><a href="#Footnote_7" class="fnanchor">[7]</a> 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:</p>
+
+<div class="footnote">
+
+<p><a name="Footnote_7" id="Footnote_7"></a><a href="#FNanchor_7"><span class="label">[7]</span></a> 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.</p></div>
+
+<p><span class="pagenum"><a name="Page_34" id="Page_34">[34]</a></span></p>
+
+<p>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<a name="FNanchor_8" id="FNanchor_8"></a><a href="#Footnote_8" class="fnanchor">[8]</a>.</p>
+
+<div class="footnote">
+
+<p><a name="Footnote_8" id="Footnote_8"></a><a href="#FNanchor_8"><span class="label">[8]</span></a> The wick&#8217;s not being uniformly twisted throughout,
+may occasion a little variation in the dimensions of the
+flame.</p></div>
+
+<p>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<span class="pagenum"><a name="Page_35" id="Page_35">[35]</a></span>
+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.</p>
+
+<p>Candles, on which Mr. <span class="smcap">Walker</span> has made
+experiments, are described in the following</p>
+
+<p class="center">TABLE.</p>
+
+<table class="nowrap" summary="Table page 35">
+
+<tr class="bt bb">
+<th class="center padl1 padr1 bl br">No.</th>
+<th class="center padl1 padr1 br">No. of<br />candles<br />to the<br />pound<br />avoir-<br />dupoise<br />weight.</th>
+<th colspan="2" class="center padl1 padr1 br">Length<br />in<br />inches.</th>
+<th class="center padl1 padr1 br">No. of<br />single<br />threads<br />of fine<br />cotton<br />in the wick.</th>
+</tr>
+
+<tr>
+<td class="center padl1 padr1 bl br">1</td>
+<td class="right padl1 padr3 br">14</td>
+<td class="right padl1 padr0">8.</td>
+<td class="left padl0 padr1 br">5</td>
+<td class="center padl1 padr1 br">10</td>
+</tr>
+
+<tr>
+<td class="center padl1 padr1 bl br">2</td>
+<td class="right padl1 padr3 br">13</td>
+<td class="right padl1 padr0">9.</td>
+<td class="br">&nbsp;</td>
+<td class="center padl1 padr1 br">12</td>
+</tr>
+
+<tr>
+<td class="center padl1 padr1 bl br">3</td>
+<td class="right padl1 padr3 br">10</td>
+<td class="right padl1 padr0">9.</td>
+<td class="left padl0 padr1 br">74</td>
+<td class="center padl1 padr1 br">14</td>
+</tr>
+
+<tr>
+<td class="center padl1 padr1 bl br">4</td>
+<td class="right padl1 padr3 br">8</td>
+<td class="right padl1 padr0">10.</td>
+<td class="br">&nbsp;</td>
+<td class="center padl1 padr1 br">20</td>
+</tr>
+
+<tr>
+<td class="center padl1 padr1 bl br">5</td>
+<td class="right padl1 padr3 br">6</td>
+<td class="right padl1 padr0">10.</td>
+<td class="left padl0 padr1 br">25</td>
+<td class="center padl1 padr1 br">24</td>
+</tr>
+
+<tr class="bb">
+<td class="center padl1 padr1 bl br">Mould</td>
+<td class="right padl1 padr3 br">6</td>
+<td class="right padl1 padr0">13.</td>
+<td class="br">&nbsp;</td>
+<td class="br">&nbsp;</td>
+</tr>
+
+</table>
+
+<p>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.</p>
+
+<p>No. 4, placed at the angle mentioned above,
+and lighted, requires no snuffing: it gives a<span class="pagenum"><a name="Page_36" id="Page_36">[36]</a></span>
+light very little stronger than No. 1, but its
+colour is not quite so white, nor its flame so
+steady.</p>
+
+<p>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.</p>
+
+<p>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.</p>
+
+<p>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,<span class="pagenum"><a name="Page_37" id="Page_37">[37]</a></span>
+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.</p>
+
+<p>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.</p>
+
+<p>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<span class="pagenum"><a name="Page_38" id="Page_38">[38]</a></span>
+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.</p>
+
+<p>Mr. <span class="smcap">Walker</span> 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.</p>
+
+<p>The following observations on this subject
+are copied from the Monthly Magazine, 1805,
+p. 206.</p>
+
+<p>&#8220;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.</p>
+
+<p><span class="pagenum"><a name="Page_39" id="Page_39">[39]</a></span></p>
+
+<p>&#8220;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.</p>
+
+<p>&#8220;But I found an obstacle to the adoption of
+Mr. <span class="smcap">Walker</span>&#8217;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.</p>
+
+<p>&#8220;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<span class="pagenum"><a name="Page_40" id="Page_40">[40]</a></span>
+in a nozzle fitting that of the candlestick.&mdash;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.&mdash;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.</p>
+
+<p>&#8220;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<span class="pagenum"><a name="Page_41" id="Page_41">[41]</a></span>
+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.</p>
+
+<p>&#8220;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.&#8221;</p>
+
+<p>Lord <span class="smcap">Stanhope</span><a name="FNanchor_9" id="FNanchor_9"></a><a href="#Footnote_9" class="fnanchor">[9]</a> has published a simple
+method of manufacturing candles, which,
+according to his Lordship&#8217;s statement, is superior
+to the method usually employed. The
+principles upon which the process depends are
+the following:&mdash;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<span class="pagenum"><a name="Page_42" id="Page_42">[42]</a></span>
+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.</p>
+
+<div class="footnote">
+
+<p><a name="Footnote_9" id="Footnote_9"></a><a href="#FNanchor_9"><span class="label">[9]</span></a> Repository of Arts, Vol. I, p. 86.</p></div>
+
+<p>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.</p>
+
+<p>The following observations will enable any
+person who is willing to try the candles manufactured
+according to Lord Stanhope&#8217;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.</p>
+
+<p><span class="pagenum"><a name="Page_43" id="Page_43">[43]</a></span></p>
+
+<p>A taper lamp, with eight threads of cotton,
+will consume in one hour <sup>225</sup>&#8260;<sub>1000</sub> oz. of spermaceti
+oil: at six shillings per gallon, the expence of
+burning twelve hours is 13.71 farthings.</p>
+
+<p>At seven shillings, it is 15.995 farthings.</p>
+
+<p>At eight shillings, it is 18.280 farthings.</p>
+
+<p>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.</p>
+
+<p>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.</p>
+
+<p>At eight shillings, it is 8.022 farthings.</p>
+
+<p>At nine shillings, it is 9.024 farthings.</p>
+
+<p><span class="pagenum"><a name="Page_44" id="Page_44">[44]</a></span></p>
+
+<p class="center">TABLE,</p>
+
+<p class="center">Exhibiting a series of experiments, made with
+a view to determine the real and comparative
+expence of burning candles of different
+sorts and sizes.</p>
+
+<table class="nowrap esmaller" summary="Table page 44">
+
+<tr class="bt">
+<th class="bl br">&nbsp;</th>
+<th colspan="2" class="center padl1 padr1 br bb">Number of<br />candles<br />in one<br />pound.</th>
+<th colspan="3" class="center padl1 padr1 br bb">Weight<br />of one<br />candle.</th>
+<th colspan="2" class="center padl1 padr1 br bb">Time<br />one<br />candle<br />lasted.</th>
+<th colspan="2" class="center padl1 padr1 br bb">The time<br />that<br />one pound<br />will last.</th>
+<th colspan="2" class="center padl1 padr1 br bb">The expence in twelve hours<br />when candles are at 12s.<br />per dozen, which also shews<br />the proportion of expence<br />at any price, per dozen.</th>
+</tr>
+
+<tr>
+<th class="bl br">&nbsp;</th>
+<th colspan="2" class="br">&nbsp;</th>
+<th class="center padl1 padr1">Oz.</th>
+<th colspan="2" class="center padl1 padr1 br">Dr.</th>
+<th class="center padl1 padr1">Hr.</th>
+<th class="center padl1 padr1 br">Min.</th>
+<th class="center padl1 padr1">Hr.</th>
+<th class="center padl1 padr1 br">Min.</th>
+<th colspan="2" class="center padl1 padr1 br">Farthings and<br />hundredth parts.</th>
+</tr>
+
+<tr>
+<td rowspan="4" class="left padl1 padr1 bl br">A small<br />wick.<br />A large<br />wick.</td>
+<td class="right padl1 padr0 bl">18</td>
+<td class="left padl0 padr1 br"><sup>3</sup>&#8260;<sub>4</sub></td>
+<td class="center padl1 padr1">0</td>
+<td class="right padl1 padr0">14</td>
+<td class="br">&nbsp;</td>
+<td class="right padl1 padr1">3</td>
+<td class="right padl1 padr2 br">15</td>
+<td class="right padl1 padr1">59</td>
+<td class="right padl1 padr2 br">26</td>
+<td class="right padl1 padr0">9</td>
+<td class="left padl0 padr1 br">.70</td>
+</tr>
+
+<tr>
+<td class="right padl1 padr0 bl">19</td>
+<td class="br">&nbsp;</td>
+<td class="center padl1 padr1">0</td>
+<td class="right padl1 padr0">13</td>
+<td class="left padl0 padr1 br"><sup>1</sup>&#8260;<sub>2</sub></td>
+<td class="right padl1 padr1">2</td>
+<td class="right padl1 padr2 br">40</td>
+<td class="right padl1 padr1">50</td>
+<td class="right padl1 padr2 br">34</td>
+<td class="right padl1 padr0">11</td>
+<td class="left padl0 padr1 br">.40</td>
+</tr>
+
+<tr>
+<td class="right padl1 padr0 bl">16</td>
+<td class="left padl0 padr1 br"><sup>1</sup>&#8260;<sub>2</sub></td>
+<td class="center padl1 padr1">0</td>
+<td class="right padl1 padr0">15</td>
+<td class="left padl0 padr1 br"><sup>1</sup>&#8260;<sub>2</sub></td>
+<td class="right padl1 padr1">2</td>
+<td class="right padl1 padr2 br">40</td>
+<td class="right padl1 padr1">44</td>
+<td class="right padl1 padr2 br">2</td>
+<td class="right padl1 padr0">13</td>
+<td class="left padl0 padr1 br">.08</td>
+</tr>
+
+<tr>
+<td class="right padl1 padr0 bl">12</td>
+<td class="br">&nbsp;</td>
+<td class="center padl1 padr1">1</td>
+<td class="right padl1 padr0">5</td>
+<td class="left padl0 padr1 br"><sup>1</sup>&#8260;<sub>4</sub></td>
+<td class="right padl1 padr1">3</td>
+<td class="right padl1 padr2 br">27</td>
+<td class="right padl1 padr1">41</td>
+<td class="right padl1 padr2 br">24</td>
+<td class="right padl1 padr0">13</td>
+<td class="left padl0 padr1 br">.92</td>
+</tr>
+
+<tr>
+<td rowspan="6" class="bl br">&nbsp;</td>
+<td class="right padl1 padr0 bl">10</td>
+<td class="left padl0 padr1 br"><sup>3</sup>&#8260;<sub>4</sub></td>
+<td class="center padl1 padr1">1</td>
+<td class="right padl1 padr0">8</td>
+<td class="br">&nbsp;</td>
+<td class="right padl1 padr1">3</td>
+<td class="right padl1 padr2 br">36</td>
+<td class="right padl1 padr1">38</td>
+<td class="right padl1 padr2 br">24</td>
+<td class="right padl1 padr0">15</td>
+<td class="left padl0 padr1 br">.00</td>
+</tr>
+
+<tr>
+<td class="right padl1 padr0 bl">7</td>
+<td class="left padl0 padr1 br"><sup>3</sup>&#8260;<sub>4</sub></td>
+<td class="center padl1 padr1">2</td>
+<td class="right padl1 padr0">1</td>
+<td class="br">&nbsp;</td>
+<td class="right padl1 padr1">4</td>
+<td class="right padl1 padr2 br">9</td>
+<td class="right padl1 padr1">32</td>
+<td class="right padl1 padr2 br">12</td>
+<td class="right padl1 padr0">17</td>
+<td class="left padl0 padr1 br">.88</td>
+</tr>
+
+<tr>
+<td class="right padl1 padr0 bl">8</td>
+<td class="br">&nbsp;</td>
+<td class="center padl1 padr1">2</td>
+<td class="right padl1 padr0">0</td>
+<td class="br">&nbsp;</td>
+<td class="right padl1 padr1">4</td>
+<td class="right padl1 padr2 br">15</td>
+<td class="right padl1 padr1">34</td>
+<td class="right padl1 padr2 br">0</td>
+<td class="right padl1 padr0">16</td>
+<td class="left padl0 padr1 br">.94</td>
+</tr>
+
+<tr>
+<td class="right padl1 padr0 bl">5</td>
+<td class="left padl0 padr1 br"><sup>3</sup>&#8260;<sub>4</sub></td>
+<td class="center padl1 padr1">2</td>
+<td class="right padl1 padr0">13</td>
+<td class="br">&nbsp;</td>
+<td class="right padl1 padr1">5</td>
+<td class="right padl1 padr2 br">19</td>
+<td class="right padl1 padr1">30</td>
+<td class="right padl1 padr2 br">15</td>
+<td class="right padl1 padr0">19</td>
+<td class="left padl0 padr1 br">.06</td>
+</tr>
+
+<tr>
+<td rowspan="2" colspan="2" class="center padl1 padr1 br">Mould<br />candles.</td>
+<td colspan="3" class="br">&nbsp;</td>
+<td rowspan="2" colspan="2" class="br">&nbsp;</td>
+<td rowspan="2" colspan="2" class="br">&nbsp;</td>
+<td rowspan="2" colspan="2" class="center padl1 padr1 br">Moulds at 14d.<br />per dozen.</td>
+</tr>
+
+<tr>
+<td colspan="3" class="center padl1 padr1 br">Each.</td>
+</tr>
+
+<tr>
+<td rowspan="3" class="left padl1 padr1 bl br">With<br />wax&#8217;d<br />wick.</td>
+<td class="right padl1 padr0 bl">3</td>
+<td class="left padl0 padr1 br"><sup>7</sup>&#8260;<sub>8</sub></td>
+<td class="center padl1 padr1">2</td>
+<td class="right padl1 padr0">12</td>
+<td class="br">&nbsp;</td>
+<td class="right padl1 padr1">7</td>
+<td class="right padl1 padr2 br">20</td>
+<td class="right padl1 padr1">42</td>
+<td class="right padl1 padr2 br">39</td>
+<td class="right padl1 padr0">15</td>
+<td class="left padl0 padr1 br">.74</td>
+</tr>
+
+<tr>
+<td class="right padl1 padr0 bl">4</td>
+<td class="br">&nbsp;</td>
+<td class="center padl1 padr1">4</td>
+<td class="right padl1 padr0">0</td>
+<td class="br">&nbsp;</td>
+<td class="right padl1 padr1">9</td>
+<td class="right padl1 padr2 br">3</td>
+<td class="right padl1 padr1">36</td>
+<td class="right padl1 padr2 br">20</td>
+<td class="right padl1 padr0">18</td>
+<td class="left padl0 padr1 br">.56</td>
+</tr>
+
+<tr class="bb">
+<td class="right padl1 padr0 bl">3</td>
+<td class="br">&nbsp;</td>
+<td class="center padl1 padr1">5</td>
+<td class="right padl1 padr0">2</td>
+<td class="left padl0 padr1 br"><sup>3</sup>&#8260;<sub>4</sub></td>
+<td class="right padl1 padr1">17</td>
+<td class="right padl1 padr2 br">30</td>
+<td class="right padl1 padr1">52</td>
+<td class="right padl1 padr2 br">30</td>
+<td class="right padl1 padr0">16</td>
+<td class="left padl0 padr1 br">.825</td>
+</tr>
+
+</table>
+
+<p>The time each candle lasted, was taken from
+an average of several trials on each size.</p>
+
+<p>It has been suggested by Dr. <span class="smcap">Franklin</span>, that
+the flame of two candles joined, gives a much
+stronger light than both of them separately.
+The same, has been observed by Mr. <span class="smcap">Warren</span>,
+to be the case with flames of gas-lights, which,<span class="pagenum"><a name="Page_45" id="Page_45">[45]</a></span>
+when combined, give a much stronger light
+than they would afford, when in a separate
+state.</p>
+
+<p>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&mdash;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.</p>
+
+<hr class="chap" />
+
+<p><span class="pagenum"><a name="Page_46" id="Page_46">[46-<br />47]</a><br /><a name="Page_47" id="Page_47"></a></span></p>
+
+<h2>PART II.</h2>
+
+<hr class="sect" />
+
+<h3>GAS-LIGHT.</h3>
+
+<hr class="sect" />
+
+<h4>PRELIMINARY OBSERVATION.</h4>
+
+<p>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 <em class="italic">gas-light</em>.</p>
+
+<p>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 &#8220;<em class="italic">Gas Light and Coke Company</em>,&#8221;
+to apply this new art of procuring light, by<span class="pagenum"><a name="Page_48" id="Page_48">[48]</a></span>
+way of experiment, on a large scale, in lighting
+the streets of the metropolis.<a name="FNanchor_10" id="FNanchor_10"></a><a href="#Footnote_10" class="fnanchor">[10]</a></p>
+
+<div class="footnote">
+
+<p><a name="Footnote_10" id="Footnote_10"></a><a href="#FNanchor_10"><span class="label">[10]</span></a> An Act for granting certain powers and authorities to
+a company to be incorporated by charter, called the &#8220;Gas
+Light and Coke Company,&#8221; for making inflammable air for
+the lighting of the streets of the metropolis, &amp;c.&mdash;Session
+1810, 50th Geo. III.</p></div>
+
+<p>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<i>l.</i> and His Majesty has the power
+of declaring the gas-light charter void, if the
+company fail to fulfil the terms of it.</p>
+
+<hr class="sect" />
+
+<p><span class="pagenum"><a name="Page_49" id="Page_49">[49]</a></span></p>
+
+<h3>THEORY<br />
+<span class="fsize60">OF</span><br />
+THE COMBUSTION OF COAL<br />
+<span class="fsize60">IN<br />
+ELUCIDATION OF THE NATURE AND PRODUCTION<br />
+OF</span><br />
+GAS LIGHT.</h3>
+
+<p>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<span class="pagenum"><a name="Page_50" id="Page_50">[50]</a></span>
+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.</p>
+
+<p>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.</p>
+
+<p>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<span class="pagenum"><a name="Page_51" id="Page_51">[51]</a></span>
+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.</p>
+
+<p>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.</p>
+
+<p>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<span class="pagenum"><a name="Page_52" id="Page_52">[52]</a></span>
+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.</p>
+
+<p>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.</p>
+
+<p>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<span class="pagenum"><a name="Page_53" id="Page_53">[53]</a></span>
+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 <a href="#Page_15">page 15</a>.</p>
+
+<p>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 <a href="#Page_15">p. 15</a>. 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<span class="pagenum"><a name="Page_54" id="Page_54">[54]</a></span>
+at the manufactory, instead of its being in the
+wick of the candle or lamp&mdash;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.</p>
+
+<p>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<span class="pagenum"><a name="Page_55" id="Page_55">[55]</a></span>
+shape, at an expence out of all proportion below
+the value of the products.</p>
+
+<hr class="sect" />
+
+<h3>SKETCH<br />
+<span class="fsize60">OF</span><br />
+THE RISE AND PROGRESS<br />
+<span class="fsize60">OF THE</span><br />
+DISCOVERY AND APPLICATION<br />
+<span class="fsize60">OF</span><br />
+COAL-GAS,<br />
+<span class="fsize60">AS A SUBSTITUTE FOR PROCURING</span><br />
+ARTIFICIAL LIGHT.</h3>
+
+<p>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.</p>
+
+<p>In the Philosophical Transactions of the<span class="pagenum"><a name="Page_56" id="Page_56">[56]</a></span>
+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.</p>
+
+<p>It is further known, that in the beginning of
+the last century, Dr. Hales<a name="FNanchor_11" id="FNanchor_11"></a><a href="#Footnote_11" class="fnanchor">[11]</a> 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.</p>
+
+<div class="footnote">
+
+<p><a name="Footnote_11" id="Footnote_11"></a><a href="#FNanchor_11"><span class="label">[11]</span></a> Vegetab. Statics, vol. I.</p></div>
+
+<p>In the year 1767, the Bishop of Llandaff<a name="FNanchor_12" id="FNanchor_12"></a><a href="#Footnote_12" class="fnanchor">[12]</a>
+examined the nature of the vapour and gazeous
+products evolved during the distillation of pit-coal.
+This learned philosopher noticed, that<span class="pagenum"><a name="Page_57" id="Page_57">[57]</a></span>
+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.</p>
+
+<div class="footnote">
+
+<p><a name="Footnote_12" id="Footnote_12"></a><a href="#FNanchor_12"><span class="label">[12]</span></a> Watson&#8217;s Chemical Essays, vol. II.</p></div>
+
+<p>The first discovery and application of the
+use of coal-gas for the purpose of illumination is
+claimed by Mr. Murdoch.</p>
+
+<p>Dr. W. Henry of Manchester, has published
+the following account<a name="FNanchor_13" id="FNanchor_13"></a><a href="#Footnote_13" class="fnanchor">[13]</a> of this discovery.</p>
+
+<div class="footnote">
+
+<p><a name="Footnote_13" id="Footnote_13"></a><a href="#FNanchor_13"><span class="label">[13]</span></a> Thompson&#8217;s System of Chemistry, vol. I. p. 52.</p></div>
+
+<p>&#8220;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<span class="pagenum"><a name="Page_58" id="Page_58">[58]</a></span>
+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&#8217;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.</p>
+
+<p><span class="pagenum"><a name="Page_59" id="Page_59">[59]</a></span></p>
+
+<p>&#8220;Mr. Murdoch&#8217;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.&#8221;</p>
+
+<p>In the year 1803 and 1804, Mr. Winsor
+exhibited at the Lyceum in London the general<span class="pagenum"><a name="Page_60" id="Page_60">[60]</a></span>
+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.</p>
+
+<p>Mr. <span class="smcap">Winsor</span>&#8217;s display of gas-lights took
+place more than two years before Mr. <span class="smcap">Murdoch</span>&#8217;s
+priority of right was heard of.</p>
+
+<p>In stating these facts I do not mean to say
+that Mr. <span class="smcap">Murdoch</span> derived the hint of applying
+the coal-gas from the previous exhibition
+of Mr. <span class="smcap">Winsor</span>, because it is quite within
+the bounds of probability that the ideas of Mr.<span class="pagenum"><a name="Page_61" id="Page_61">[61]</a></span>
+<span class="smcap">Murdoch</span> may have arisen totally independent
+of all acquaintance with Mr. <span class="smcap">Winsor</span>&#8217;s.</p>
+
+<p>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. <span class="smcap">Winsor</span> 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.<span class="pagenum"><a name="Page_62" id="Page_62">[62]</a></span>
+<span class="smcap">Winsor</span>&#8217;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.</p>
+
+<p>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.</p>
+
+<p>On the 18th of May, 1804, Mr. <span class="smcap">Frederick
+Albert Winsor</span>, 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.</p>
+
+<p>In the year 1805, Mr. <span class="smcap">Northern</span>, of Leeds,<span class="pagenum"><a name="Page_63" id="Page_63">[63]</a></span>
+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.</p>
+
+<p>&#8220;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.&mdash;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.</p>
+
+<p>&#8220;The apparatus I make use of for producing
+light is a refiner&#8217;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<span class="pagenum"><a name="Page_64" id="Page_64">[64]</a></span>
+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.</p>
+
+<p>&#8220;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.&#8221;</p>
+
+<p>Soon afterwards, Mr. <span class="smcap">Samuel Clegg</span><a name="FNanchor_14" id="FNanchor_14"></a><a href="#Footnote_14" class="fnanchor">[14]</a> of
+Manchester, Engineer, communicated an account
+of his method of lighting up manufactories<span class="pagenum"><a name="Page_65" id="Page_65">[65]</a></span>
+with gas-light to the Society of Arts,
+for which he received the silver medal.</p>
+
+<div class="footnote">
+
+<p><a name="Footnote_14" id="Footnote_14"></a><a href="#FNanchor_14"><span class="label">[14]</span></a> This gentleman is at present engineer to the Gas-Light
+Company.</p></div>
+
+<p>Since that time, the application of gas-light
+has spread rapidly, and numerous manufactories
+and other establishments have been
+lighted by coal-gas.</p>
+
+<p>In France, the application of gas-lights to
+economical purposes, was pointed out long
+before it was publicly introduced into this
+country. M. <span class="smcap">Le Bon</span> 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 <em class="italic">brevet
+d&#8217;invention</em> (patent) granted to him by the
+French government, for the art of producing
+light from wood, ignited in close vessels.</p>
+
+<p>Many other attempts have been made to
+derive advantage from the different ingredients
+of coal; but they are too obscure to
+merit particular enumeration.</p>
+
+<p>In the year 1808, Mr. <span class="smcap">Murdoch</span> presented
+to the Royal Society his account of the application
+of gas-light, and was complimented
+with Count <span class="smcap">Romford</span>&#8217;s medal for the same.</p>
+
+<p><span class="pagenum"><a name="Page_66" id="Page_66">[66]</a></span></p>
+
+<p>The following statement is taken from Mr.
+<span class="smcap">Murdoch</span>&#8217;s paper.</p>
+
+<p>&#8220;The whole of the rooms of the cotton mill
+of Mr. <span class="smcap">Lee</span>, 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. <span class="smcap">Lee</span>,
+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, (<em class="italic">see <a href="#Page_23">page 23</a></em>) 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.</p>
+
+<p>&#8220;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.</p>
+
+<p><span class="pagenum"><a name="Page_67" id="Page_67">[67]</a></span></p>
+
+<p>&#8220;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.</p>
+
+<p>&#8220;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&#8217;s mill
+will be 1250&nbsp;&times; 2 = 2500 cubic feet of gas
+per day; to produce which 700 weight of<span class="pagenum"><a name="Page_68" id="Page_68">[68]</a></span>
+cannel-coal is required in the retort. The price
+of the best Wiggan cannel-coal (the sort used)
+is 13<sup>1</sup>&#8260;<sub>2</sub><i>d.</i> per cwt. (22<i>s.</i> 6<i>d.</i> 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<i>l.</i></p>
+
+<p>&#8220;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<i>l.</i></p>
+
+<p>&#8220;The 110 tons of cannel-coal, when distilled,
+produce about 70 tons of good coke, which is
+sold upon the spot at 1<i>s.</i> 4<i>d.</i> per cwt. and will
+therefore amount annually to the sum of 93<i>l.</i></p>
+
+<p>&#8220;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.</p>
+
+<p>&#8220;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. <span class="smcap">Lee</span> at about
+550<i>l.</i> per annum, in which some allowance is<span class="pagenum"><a name="Page_69" id="Page_69">[69]</a></span>
+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.</p>
+
+<p>&#8220;Mr. <span class="smcap">Lee</span> 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.</p>
+
+<p>&#8220;The economical statement for one year,
+then, stands thus:</p>
+
+<table summary="Table page 69">
+
+<tr>
+<td class="left top padr3">Cost of 110 tons of cannel coal</td>
+<td class="right bot">&pound;&nbsp;125</td>
+</tr>
+
+<tr>
+<td class="left top padr3">Ditto of 40 tons of common ditto, to carbonise</td>
+<td class="right bot bb">20</td>
+</tr>
+
+<tr>
+<td class="left top padr3">In all</td>
+<td class="right bot bb">145</td>
+</tr>
+
+<tr>
+<td class="left top padr3">Deduct the value of 70 tons of coke</td>
+<td class="right bot">93</td>
+</tr>
+
+<tr>
+<td class="left top padr3">The annual expenditure in coal, after deducting the value of the coke, and without allowing any thing for the tar, is therefore</td>
+<td class="right bot">52</td>
+</tr>
+
+<tr>
+<td class="left top padr3">And the interest of capital sunk, and wear and tear of apparatus</td>
+<td class="right bot">550</td>
+</tr>
+
+<tr>
+<td class="left top padr3">Making the total expence of the gas apparatus per annum, about</td>
+<td class="right bot">600</td>
+</tr>
+
+</table>
+
+<p>&#8220;That of candles, to give the same light,<span class="pagenum"><a name="Page_70" id="Page_70">[70]</a></span>
+would be about 2000<i>l.</i> 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.</p>
+
+<p>&#8220;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<i>l.</i> while that of the tallow would be
+3000<i>l.</i>&#8221;</p>
+
+<p>Mr. <span class="smcap">Ackerman</span> 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. <span class="smcap">Ackerman</span>&#8217;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:</p>
+
+<p><span class="pagenum"><a name="Page_71" id="Page_71">[71]</a></span></p>
+
+<blockquote>
+
+<p class="center">To <span class="smcap">Mr.</span> ACCUM.</p>
+
+<p><span class="smcap">Sir</span>,</p>
+
+<p>&#8220;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&#8217;s lamps, of the large size, for four
+hours per night, during the long winter evenings, together with
+eight Argand&#8217;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.</p>
+
+<p>Now 365 retorts containing 120lb. of coal each, make 43800lb.
+which is equal to ten chaldrons of Newcastle and eight tons of
+cannel coal.</p>
+
+<table summary="Table page 71">
+
+<tr>
+<td class="right top padr1" style="width: 1em;">10</td>
+<td colspan="3" class="left top padr3">chaldrons of Newcastle coals, at 65s. make</td>
+<td class="right bot padl1 padr1">&pound;&nbsp;32</td>
+<td class="right bot padl1 padr1">10</td>
+<td class="right bot padl1 padr1">0</td>
+</tr>
+
+<tr>
+<td class="right top padr1">8</td>
+<td colspan="3" class="left top padr3">tons of cannel coal,<a name="FNanchor_15" id="FNanchor_15"></a><a href="#Footnote_15" class="fnanchor">[15]</a> (this coal is sold by weight) at 100s. per ton</td>
+<td class="right bot padl1 padr1">40</td>
+<td class="right bot padl1 padr1">0</td>
+<td class="right bot padl1 padr1">0</td>
+</tr>
+
+<tr>
+<td class="right top padr1">7</td>
+<td colspan="3" class="left top padr3">chaldrons of common coals for carbonising, at 55s.</td>
+<td class="right bot padl1 padr1">19</td>
+<td class="right bot padl1 padr1">5</td>
+<td class="right bot padl1 padr1">0</td>
+</tr>
+
+<tr>
+<td colspan="4" class="left top padr3">To wages paid the servant for attending the gas apparatus</td>
+<td class="right bot padl1 padr1">30</td>
+<td class="right bot padl1 padr1">0</td>
+<td class="right bot padl1 padr1">0</td>
+</tr>
+
+<tr>
+<td colspan="4" class="left top padr3">Interest of money sunk</td>
+<td class="right bot padl1 padr1">30</td>
+<td class="right bot padl1 padr1">0</td>
+<td class="right bot padl1 padr1">0</td>
+</tr>
+
+<tr>
+<td>&nbsp;</td>
+<td colspan="3" class="left top padr3">The wear and tear of the gas-light apparatus I consider to be equal to the wear and tear of lamps, candlesticks, &amp;c. employed for oil, tallow, &amp;c.</td>
+<td colspan="3" class="bb">&nbsp;</td>
+</tr>
+
+<tr>
+<td colspan="4" class="right top padr3">Total expence of the gas lights</td>
+<td class="right bot padl1 padr1">151</td>
+<td class="right bot padl1 padr1">15</td>
+<td class="right bot padl1 padr1">0</td>
+</tr>
+
+<tr>
+<td colspan="7" class="center top blankabove blankbelow">DEDUCT</td>
+</tr>
+
+<tr>
+<td class="right top padr1">23</td>
+<td class="left top padr3">chaldrons of coke, at 60s. per chaldron</td>
+<td class="right bot padl1 padr1">69</td>
+<td colspan="4">&nbsp;</td>
+</tr>
+
+<tr>
+<td colspan="2" class="left top padr3">Ammoniacal liquor</td>
+<td class="right bot padl1 padr1">5</td>
+<td colspan="4">&nbsp;</td>
+</tr>
+
+<tr>
+<td colspan="2" class="left top padr3">Tar</td>
+<td class="right bot padl1 padr1">6</td>
+<td colspan="4">&nbsp;</td>
+</tr>
+
+<tr>
+<td colspan="2" class="left top padr3">Charcoal employed by the copper-plate printers to heat their plates, which is now done with the gas-light flame, cost, annually</td>
+<td class="right bot padl1 padr1">25</td>
+<td colspan="4">&nbsp;</td>
+</tr>
+
+<tr>
+<td colspan="2" class="left top padr3">Two chaldrons of coals <em class="italic">minus</em> used as fuel, for warming the house, since the adoption of the gas-lights, at 65s. per chaldron</td>
+<td class="right bot padl1 padr1 bb">6</td>
+<td class="right bot padl1 padr1 bb">10</td>
+<td colspan="3">&nbsp;</td>
+</tr>
+
+<tr>
+<td colspan="4">&nbsp;</td>
+<td class="right bot padl1 padr1 bb">111</td>
+<td class="right bot padl1 padr1 bb">10</td>
+<td class="right bot padl1 padr1 bb">0</td>
+</tr>
+
+<tr>
+<td colspan="4" class="right top padr3">Nett expences of the gas-lights</td>
+<td class="right bot padl1 padr1 bb">&pound;&nbsp;40</td>
+<td class="right bot padl1 padr1 bb">5</td>
+<td class="right bot padl1 padr1 bb">0</td>
+</tr>
+
+<tr>
+<td colspan="4" class="left top padr3">The lights used in my Establishment, prior to the gas-lights, amounted annually to</td>
+<td class="right bot padl1 padr1">160</td>
+<td class="right bot padl1 padr1">0</td>
+<td class="right bot padl1 padr1">0</td>
+</tr>
+
+<tr>
+<td colspan="4" class="left top padr3">My present system of lighting with gas costs, per ann.</td>
+<td class="right bot padl1 padr1 bb">40</td>
+<td class="right bot padl1 padr1 bb">5</td>
+<td class="right bot padl1 padr1 bb">0</td>
+</tr>
+
+<tr>
+<td colspan="4" class="right top padr3">Balance in favor of the gas for one year</td>
+<td class="right bot padl1 padr1">&pound;&nbsp;119</td>
+<td class="right bot padl1 padr1">15</td>
+<td class="right bot padl1 padr1">0</td>
+</tr>
+
+</table>
+
+</blockquote>
+
+<div class="footnote">
+
+<p><a name="Footnote_15" id="Footnote_15"></a><a href="#FNanchor_15"><span class="label">[15]</span></a> <em class="italic">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.</em></p></div>
+
+<p><span class="pagenum"><a name="Page_72" id="Page_72">[72]</a></span></p>
+
+<blockquote>
+
+<p>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, &amp;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&#8217;s lamps or candles,
+would cost at least 350l. per annum.</p>
+
+<p class="center">I am, with respect,<br />
+Yours,</p>
+
+<p class="placedate">Strand, March 13,<br />
+1815.</p>
+
+<p class="signature">R. ACKERMAN.&#8221;</p>
+
+</blockquote>
+
+<p>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.
+<span class="smcap">Cook</span>, 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 <em class="italic">na&iuml;vet&eacute;</em> in his own
+account of the process which will amuse as well
+as instruct the reader.</p>
+
+<p>&#8220;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<span class="pagenum"><a name="Page_73" id="Page_73">[73]</a></span>
+make perhaps six hundred gallons<a name="FNanchor_16" id="FNanchor_16"></a><a href="#Footnote_16" class="fnanchor">[16]</a> 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;&mdash;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.&#8221;</p>
+
+<div class="footnote">
+
+<p><a name="Footnote_16" id="Footnote_16"></a><a href="#FNanchor_16"><span class="label">[16]</span></a> A wine-gallon is equal to 231 cubic inches.</p></div>
+
+<p>Thus are the candles which Mr. <span class="smcap">Cook</span> 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<i>l.</i> a year; which
+is entirely saved, as he now does all his soldering
+by the gas flame only. For &#8220;in all
+trades in which the blow-pipe is used with oil<span class="pagenum"><a name="Page_74" id="Page_74">[74]</a></span>
+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.&#8221; We must
+refer to Mr. <span class="smcap">Cook</span>&#8217;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<i>l.</i> out of the 50<i>l.</i> 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, &#8220;the saving,&#8221;
+Mr. <span class="smcap">Cook</span> assures us, &#8220;will still be considerable:<span class="pagenum"><a name="Page_75" id="Page_75">[75]</a></span>
+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<i>l.</i> or 12<i>l.</i> which he will nearly, if not
+quite, save the first year.&#8221;</p>
+
+<p>Mr. <span class="smcap">Ackerman</span> 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.
+<span class="smcap">Lloyd</span>, of Queen Street, Southwark, thimble
+manufacturers and whitesmiths, who have used
+the gas-light for soldering and other purposes
+these five years past.</p>
+
+<table summary="Table page 75-76">
+
+<tr>
+<td class="left top padr3">From 4 pecks or 1 bushel of coals, weighing 69lbs. for which we now pay (1809) 1s. we produce 4<sup>3</sup>&#8260;<sub>4</sub> pecks of coke and <sup>1</sup>&#8260;<sub>2</sub> peck of coal not carbonised remains in the distilling pot, which together with the coke weighs 58lbs. 6 oz. value at 1s. per bushel</td>
+<td class="right bot padl1 padr1">0</td>
+<td class="right bot padl1 padr1">1</td>
+<td class="right bot padl1 padr1">4</td>
+</tr>
+
+<tr>
+<td class="left top padr3">we procure 6lbs. 4 oz. of tar which<span class="pagenum"><a name="Page_76" id="Page_76">[76]</a></span> we use as pith&mdash;it saves us</td>
+<td class="right bot padl1 padr1 bb">0</td>
+<td class="right bot padl1 padr1 bb">1</td>
+<td class="right bot padl1 padr1 bb">0</td>
+</tr>
+
+<tr>
+<td>&nbsp;</td>
+<td class="right bot padl1 padr1">0</td>
+<td class="right bot padl1 padr1">2</td>
+<td class="right bot padl1 padr1">4</td>
+</tr>
+
+<tr>
+<td class="center top">Deduct for coal</td>
+<td class="right bot padl1 padr1 bb">0</td>
+<td class="right bot padl1 padr1 bb">1</td>
+<td class="right bot padl1 padr1 bb">0</td>
+</tr>
+
+<tr>
+<td class="left top padr3">Profit on coke and tar</td>
+<td class="right bot padl1 padr1 bb">0</td>
+<td class="right bot padl1 padr1 bb">1</td>
+<td class="right bot padl1 padr1 bb">0</td>
+</tr>
+
+<tr>
+<td class="left top padr3">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</td>
+<td class="right bot padl1 padr1">0</td>
+<td class="right bot padl1 padr1">7</td>
+<td class="right bot padl1 padr1">0</td>
+</tr>
+
+<tr>
+<td class="left top padr3">To this, add profits on coke and tar</td>
+<td class="right bot padl1 padr1 bb">0</td>
+<td class="right bot padl1 padr1 bb">1</td>
+<td class="right bot padl1 padr1 bb">0</td>
+</tr>
+
+<tr>
+<td class="left top padr3">Gained out of every bushel of coal</td>
+<td class="right bot padl1 padr1 bb">0</td>
+<td class="right bot padl1 padr1 bb">8</td>
+<td class="right bot padl1 padr1 bb">0</td>
+</tr>
+
+</table>
+
+<p>&#8220;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&#8217;s lamps. We are not nice concerning
+the quality of the gas&mdash;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.&#8221;</p>
+
+<hr class="sect" />
+
+<p><span class="pagenum"><a name="Page_77" id="Page_77">[77]</a></span></p>
+
+<h3>THEORY<br />
+<span class="fsize60">OF</span><br />
+THE PRODUCTION OF GAS-LIGHT,<br />
+<span class="fsize60">AND</span><br />
+DESCRIPTION<br />
+<span class="fsize60">OF</span><br />
+A PORTABLE APPARATUS<br />
+<span class="fsize60">FOR EXHIBITING, IN THE SMALL WAY, THE GENERAL<br />
+NATURE OF THIS SPECIES OF LIGHT.</span></h3>
+
+<p>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, &amp;c. The liquid substances
+are conveyed into proper vessels, and
+the gazeous products are conducted, by means
+of pipes, under the gasometer, where the<span class="pagenum"><a name="Page_78" id="Page_78">[78]</a></span>
+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<span class="pagenum"><a name="Page_79" id="Page_79">[79]</a></span>
+which the gas alone can issue, thus forming
+small distinct streams of light.</p>
+
+<div class="figcenter"><a name="Plate2" id="Plate2"></a>
+<img src="images/illo093.jpg" alt="Gas-apparatus" width="600" height="383" />
+<p class="largeimg"><a href="images/lg093.jpg">Larger image</a> (279 kB)</p>
+</div>
+
+<p>The gas-apparatus, <a href="#Plate2">plate 2</a>, 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.</p>
+
+<p>It consists of three distinct apparatus:&mdash;namely,
+a portable furnace, <a href="#Plate2">fig. 1, plate 2</a>, by
+means of which the gas is prepared&mdash;<a href="#Plate2">fig. 2</a>, 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&mdash;<a href="#Plate2">fig.
+3</a>, 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:&mdash;<i>a</i>,
+represents a cast iron retort, such as
+is used for chemical operations in the small<span class="pagenum"><a name="Page_80" id="Page_80">[80]</a></span>
+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. <i>b.</i> is a metal pipe which conveys
+all the distillatory products from the retort into
+the purifier <a href="#Plate2">fig. 2</a>. This tube is bent at right
+angles at the extremity where it enters the intermediate
+vessel <a href="#Plate2">fig. 2</a>. The purifier <a href="#Plate2">fig. 2</a>, is
+divided into three compartments marked <i>c.</i> <i>d.</i> <i>e.</i>
+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, <i>d</i>, 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<span class="pagenum"><a name="Page_81" id="Page_81">[81]</a></span>
+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 <i>e</i> is left empty
+to receive the tar and other liquid products.
+Into the first compartment <i>c</i>, all the gazeous
+and liquid products are delivered, as they
+become evolved during the distillation, by
+means of the pipe <i>b</i>. The compartment <i>d</i>, 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 <i>b</i>, to pass readily
+through it. From the chamber <i>c</i>, the liquid
+and gazeous products pass to the tar-chamber,
+or compartment <i>e</i>, by means of the descending
+pipe <i>f</i>. The tar and other condensible substances
+are therefore deposited at <i>e</i>, whilst the
+gazeous products alone ascend from the tar-chamber
+<i>e</i>, by the pipe <i>g</i>, and down again
+the pipe <i>h</i>, (which is closed at the top) into
+the compartment <i>d</i>, of the vessel or purifier,
+<a href="#Plate2">fig. 2</a>. The gas being thus made to pass from
+the compartment <i>e</i>, up into the pipe <i>g</i>, and
+down the pipe <i>h</i>, (which is closed at the top)
+into the purifier <i>d</i>, is brought into contact with<span class="pagenum"><a name="Page_82" id="Page_82">[82]</a></span>
+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 <i>c</i>, 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&mdash;<i>i</i>
+is another wide-mouth funnel, by
+means of which the chamber <i>d</i>, 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 <i>d</i>, of the
+purifier, forming carbonate and hidro-sulphuret
+of lime. The carburetted hidrogen, being
+left more or less pure, is conveyed through the
+pipe <i>k</i>, into the gasometer, <a href="#Plate2">fig. 3</a>. The communication
+of the purifier, <a href="#Plate2">fig. 2</a>, with the gasometer,
+is made by means of the well-known
+water-valve <i>l</i>, placed so that the communicating
+tube <i>k</i>, may be easily removed at pleasure&mdash;<i>m</i>,
+is a cock for drawing off the tar, &amp;c.
+<i>n</i>, a gauge-cock for ascertaining the height of<span class="pagenum"><a name="Page_83" id="Page_83">[83]</a></span>
+the liquid in the chamber <i>d</i>. The gasometer,
+<a href="#Plate2">fig. 3</a>, the object of which is to store up the
+gas, consists of two principal parts&mdash;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. <i>o</i> is a
+pipe, which communicates with the water-valve
+<i>l</i>, and by means of which the gas passes
+from the purifier, <a href="#Plate2">fig. 2</a>, into the gasometer.
+The upper end of this pipe is covered, in the
+manner of a hood, by a cylindrical vessel <i>p</i>,
+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 <i>p</i>, 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, &amp;c.
+After rising through the water the gas enters<span class="pagenum"><a name="Page_84" id="Page_84">[84]</a></span>
+the gasometer, which is suspended to move up
+and down by the chains, pullies, and balance-weights,
+<i>q</i>. From the centre of the gasometer
+a tube, <i>r</i>, descends, which includes a pipe, <i>s</i>,
+fixed perpendicular from the bottom of the
+cistern. The fixed pipe <i>r</i>, forms a guide to
+keep the gasometer always perpendicular. <i>t</i> is
+also an iron pipe made fast in the centre of the
+inner vessel, and communicates with the upright
+tube, <i>s</i>, in the outer vessel. This contrivance
+obliges the gas to pass into the pipe <i>t</i>,
+whilst it also serves to keep the gasometer
+steady when nearly out of the outer cistern.</p>
+
+<p>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 <i>q</i> <i>q</i>, 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 <i>o</i>, into
+the vessel, <i>p</i>, from which it displaces the
+water, and passes out at the small holes, as<span class="pagenum"><a name="Page_85" id="Page_85">[85]</a></span>
+before described, rising through the water into
+the gasometer, and raising it up: the gas then
+passes away to the burners, <i>u</i> <i>u</i>. 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. <i>v</i> <i>v</i> are cocks to let off any
+liquid that may collect in the pipe <i>o</i> or <i>t</i>; 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&mdash;they would,
+as it is called, <em class="italic">dance</em>, or become extinguished.
+<i>x</i> is the main stop-cock which communicates
+with the burners&mdash;these, of course, may be
+placed as convenience may require. <i>z</i> <i>z</i> are
+two projecting parts in the top of the gasometer;<span class="pagenum"><a name="Page_86" id="Page_86">[86]</a></span>
+they are intended to receive the hood <i>p</i>,
+and the upper extremity of the pipe <i>t</i>, 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.</p>
+
+<p>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<span class="pagenum"><a name="Page_87" id="Page_87">[87]</a></span>
+of the size of the flames; which could
+not be rendered uniform.</p>
+
+<p>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.</p>
+
+<p>To compensate for this increasing weight of
+the gasometer, and render a scale of equal
+graduations accurate, some have ingeniously<span class="pagenum"><a name="Page_88" id="Page_88">[88]</a></span>
+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.</p>
+
+<p>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.</p>
+
+<p>Pit-coal is not the only substance which affords
+carburetted hydrogen; this gazeous fluid<span class="pagenum"><a name="Page_89" id="Page_89">[89]</a></span>
+may be obtained in a great variety of ways,
+and with very considerable differences in specific
+gravity and proportion of ingredients.</p>
+
+<p>It is found plentifully native or ready formed
+on the surface of stagnant waters, marshes, wet
+ditches, &amp;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.</p>
+
+<p>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 <em class="italic">ignis fatuus</em> 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.</p>
+
+<p>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<span class="pagenum"><a name="Page_90" id="Page_90">[90]</a></span>
+into the bottle; when by thus stirring the mud
+in various places, the air may be catched in the
+bottle.</p>
+
+<p>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.</p>
+
+<p>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
+(<span class="smcap">Van Dieman</span>, <span class="smcap">Troostwyck</span>, 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.<span class="pagenum"><a name="Page_91" id="Page_91">[91]</a></span>
+Hence it has been termed oily carburetted hidrogen,
+or olifiant gas&mdash;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&mdash;its taste somewhat sweet&mdash;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.</p>
+
+<p>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<span class="pagenum"><a name="Page_92" id="Page_92">[92]</a></span>
+air as 2 to 3&mdash;112lb. of common cannel coal produce
+at its <em class="italic">minimum</em>, 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) <span class="division"><span class="num">7000</span><span class="denom">175</span></span> = 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,<span class="pagenum"><a name="Page_93" id="Page_93">[93]</a></span>
+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 <em class="italic">minimum</em>,
+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 <span class="division"><span class="num">350</span><span class="denom">20</span></span> =
+17<sup>1</sup>&#8260;<sub>2</sub>lbs. 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.</p>
+
+<p>With regard to Newcastle coals<a name="FNanchor_17" id="FNanchor_17"></a><a href="#Footnote_17" class="fnanchor">[17]</a>, it may be
+stated that one chaldron of Wall&#8217;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.</p>
+
+<div class="footnote">
+
+<p><a name="Footnote_17" id="Footnote_17"></a><a href="#FNanchor_17"><span class="label">[17]</span></a> One chaldron of Newcastle coal weighs from 2850 to
+upwards of 2978lb.</p></div>
+
+<p>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<span class="pagenum"><a name="Page_94" id="Page_94">[94]</a></span>
+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.<a name="FNanchor_18" id="FNanchor_18"></a><a href="#Footnote_18" class="fnanchor">[18]</a></p>
+
+<div class="footnote">
+
+<p><a name="Footnote_18" id="Footnote_18"></a><a href="#FNanchor_18"><span class="label">[18]</span></a> One pound of coal-tar produces 15 cubic feet of carburetted
+hidrogen abounding in olifiant gas.</p></div>
+
+<p>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.</p>
+
+<p>The retorts best calculated for large gas-light
+works are seven or eight foot long (without the
+mouth-piece) and twelve inches in diameter,<span class="pagenum"><a name="Page_95" id="Page_95">[95]</a></span>
+tapering down to ten inches&mdash;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&mdash;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&mdash;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;<a name="FNanchor_19" id="FNanchor_19"></a><a href="#Footnote_19" class="fnanchor">[19]</a> 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<span class="pagenum"><a name="Page_96" id="Page_96">[96]</a></span>
+an intolerable suffocating odour, when the gas
+is burnt which is particularly perceptible in low
+rooms illuminated with such gas.</p>
+
+<div class="footnote">
+
+<p><a name="Footnote_19" id="Footnote_19"></a><a href="#FNanchor_19"><span class="label">[19]</span></a> It is chiefly a mixture of carbonic oxid, and hydrogen gas.</p></div>
+
+<p>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.</p>
+
+<p>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.</p>
+
+<p>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.
+<sup>1</sup>&#8260;<sub>27</sub> part of its own bulk of pure coal-gas<span class="pagenum"><a name="Page_97" id="Page_97">[97]</a></span>
+is absorbed by the water over which it is confined
+in the gazometer.</p>
+
+<p>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.</p>
+
+<p>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<span class="pagenum"><a name="Page_98" id="Page_98">[98]</a></span>
+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.</p>
+
+<p>&#8220;Messrs. <span class="smcap">Sobolewsky</span> and <span class="smcap">Horrer</span>, 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<span class="pagenum"><a name="Page_99" id="Page_99">[99]</a></span>
+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.&#8221;<a name="FNanchor_20" id="FNanchor_20"></a><a href="#Footnote_20" class="fnanchor">[20]</a></p>
+
+<div class="footnote">
+
+<p><a name="Footnote_20" id="Footnote_20"></a><a href="#FNanchor_20"><span class="label">[20]</span></a> See Repository of Arts, Vol. XI. No. 36, p. 341.</p></div>
+
+<hr class="sect" />
+
+<h3>UTILITY<br />
+<span class="fsize60">OF THE</span><br />
+GAS-LIGHT ILLUMINATION,<br />
+<span class="fsize60">WITH REGARD TO</span><br />
+PUBLIC AND PRIVATE ECONOMY.</h3>
+
+<p>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<span class="pagenum"><a name="Page_100" id="Page_100">[100]</a></span>
+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&mdash;no disturbance
+in the transparency of the atmosphere&mdash;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<span class="pagenum"><a name="Page_101" id="Page_101">[101]</a></span>
+in all our common lights. The products
+of the combustion are water and carbonic acid
+gas<a name="FNanchor_21" id="FNanchor_21"></a><a href="#Footnote_21" class="fnanchor">[21]</a>. The accurate and elegant experiments
+of Dr. W. <span class="smcap">Henry</span> 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<a name="FNanchor_22" id="FNanchor_22"></a><a href="#Footnote_22" class="fnanchor">[22]</a>, which<span class="pagenum"><a name="Page_102" id="Page_102">[102]</a></span>
+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&mdash;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.</p>
+
+<div class="footnote">
+
+<p><a name="Footnote_21" id="Footnote_21"></a><a href="#FNanchor_21"><span class="label">[21]</span></a> 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.</p></div>
+
+<div class="footnote">
+
+<p><a name="Footnote_22" id="Footnote_22"></a><a href="#FNanchor_22"><span class="label">[22]</span></a> 100 Cubic inches of carburetted hydrogen from coal,
+require for burning 220 cubic inches of oxygen and produce
+100 cubic inches of carbonic acid&mdash;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&mdash;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.
+</p>
+<blockquote>
+
+<p>The following lines relating to the salubrity of the gas-light illumination
+are copied from Mr. Lee&#8217;s evidence in the House of
+Commons, when examined on that subject.
+</p>
+<p>
+Question&mdash;&#8220;Is the health of your manufacturers at all affected
+by the use of gas?&mdash;Answer&mdash;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.&#8221;
+</p>
+<p>
+Q. &#8220;You have not seen the smallest alteration in the health
+of your workmen?&mdash;A. Not in the least, for had I seen it, it
+would have been a fatal objection to it.&#8221;
+</p>
+<p>
+Q. &#8220;And you say the same in regard to the use of the gas-lights
+in your own family?&mdash;A. Certainly I do.&#8221;</p></blockquote>
+</div>
+
+<p>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&#8217;s lamps.</p>
+
+<p><span class="pagenum"><a name="Page_103" id="Page_103">[103]</a></span></p>
+
+<p>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.</p>
+
+<p>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<span class="pagenum"><a name="Page_104" id="Page_104">[104]</a></span>
+by the stand or support of the combustible
+matter.</p>
+
+<p>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, &amp;c.</p>
+
+<p>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.</p>
+
+<p>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.</p>
+
+<p>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<span class="pagenum"><a name="Page_105" id="Page_105">[105]</a></span>
+house. When transparencies are wanted as
+decorations for halls, lobbies, &amp;c. more than
+light, recesses may be filled with different coloured
+<em class="italic">media</em>, or paintings, and any intensity of
+light may be thrown on the object.</p>
+
+<p>If a number of minute holes are made in
+the end of a gas pipe, it forms as many <i lang="fr" xml:lang="fr">jets
+de feu</i>, 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.</p>
+
+<p>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.</p>
+
+<p>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<span class="pagenum"><a name="Page_106" id="Page_106">[106]</a></span>
+night of a general illumination, compared with
+the glimmering light of its ordinary parish
+lamps.</p>
+
+<p>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.</p>
+
+<p>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.</p>
+
+<p>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,<span class="pagenum"><a name="Page_107" id="Page_107">[107]</a></span>
+no doubt will pay all its expences besides the
+interest of capital, and leave a surplus of profit.</p>
+
+<p>Indeed the application of the coal-gas, as a
+substitute for tallow and oil, to illuminate
+houses, shops, &amp;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.<a name="FNanchor_23" id="FNanchor_23"></a><a href="#Footnote_23" class="fnanchor">[23]</a></p>
+
+<div class="footnote">
+
+<p><a name="Footnote_23" id="Footnote_23"></a><a href="#FNanchor_23"><span class="label">[23]</span></a> The Liberty of Norton Falgate, as far as Bishopgate-street, is
+lighted with gas-light, from the Chartered Company&#8217;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.
+</p>
+<p>
+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&#8217;s in
+the Field. Main pipes are also placed in the Hay-market, Coventry-street,
+Long-Acre, St. Martin&#8217;s-lane; and in the principal
+parts of the parishes of St. James and St. Ann.
+</p>
+<p>
+In the East end of the metropolis, the gas-light <em class="italic">mains</em> extend
+from Cornhill to St. Paul&#8217;s, Wood-street, Fore-street, &amp;c.&mdash;Consent
+has also been given to the incorporated Gas-Light Company
+for laying their pipes in the parish of St. Stephen&#8217;s in the
+Field; St. Paul Covent-garden; St. Mary-le-Strand; St. Clement
+Danes; St. George&#8217;s, Bloomsbury; St. Giles&#8217;s in the
+Fields; St. Andrew&#8217;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.</p></div>
+
+<p>Enough therefore, has been done to prove the
+possibility of lighting houses, and streets, with<span class="pagenum"><a name="Page_108" id="Page_108">[108]</a></span>
+gas, which would have been regarded twenty
+years ago as an extravagant paradox.<a name="FNanchor_24" id="FNanchor_24"></a><a href="#Footnote_24" class="fnanchor">[24]</a></p>
+
+<div class="footnote">
+
+<p><a name="Footnote_24" id="Footnote_24"></a><a href="#FNanchor_24"><span class="label">[24]</span></a> I am informed by Mr. <span class="smcap">Clegg</span>, 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.
+</p>
+
+<blockquote>
+
+<p>In the Eastern part of London, the same Company is engaged
+to lay their pipes in the principal parts of Whitechapel, Spitalfields,
+St. Luke&#8217;s, and the adjoining neighbourhood.
+</p>
+<p>
+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.</p></blockquote>
+</div>
+
+<p>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.</p>
+
+<p><span class="pagenum"><a name="Page_109" id="Page_109">[109]</a></span></p>
+
+<p>Another advantageous application of the gas-light
+must be the supplying of light-houses.</p>
+
+<p>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.</p>
+
+<p>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.</p>
+
+<p>The ease with which the largest gas-light
+flame is instantly extinguished by shutting the<span class="pagenum"><a name="Page_110" id="Page_110">[110]</a></span>
+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.</p>
+
+<p>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.</p>
+
+<p>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.</p>
+
+<p><span class="pagenum"><a name="Page_111" id="Page_111">[111]</a></span></p>
+
+<p>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.</p>
+
+<p>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.</p>
+
+<p>The heat produced by gas-lights must be
+observed by every one who has had an opportunity<span class="pagenum"><a name="Page_112" id="Page_112">[112]</a></span>
+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.</p>
+
+<p>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.</p>
+
+<p>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.</p>
+
+<p>From trials made on this subject, I am enabled<span class="pagenum"><a name="Page_113" id="Page_113">[113]</a></span>
+to state, that three Argand&#8217;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.<a name="FNanchor_25" id="FNanchor_25"></a><a href="#Footnote_25" class="fnanchor">[25]</a></p>
+
+<div class="footnote">
+
+<p><a name="Footnote_25" id="Footnote_25"></a><a href="#FNanchor_25"><span class="label">[25]</span></a> Mr. <span class="smcap">Dalton</span>&#8217;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:
+</p>
+<p>
+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.
+</p>
+<p>
+It was thus proved that&mdash;
+</p>
+
+<table summary="Table footnote 25">
+
+<tr>
+<td class="left top padr3">Olefiant gas raises an equal volume of water</td>
+<td class="left bot">14&deg;</td>
+</tr>
+
+<tr>
+<td class="left top padr3">Carburetted hidrogen, or coal gas</td>
+<td class="left bot">10</td>
+</tr>
+
+<tr>
+<td class="left top padr3">Carbonic oxid</td>
+<td class="left bot">4</td>
+</tr>
+
+<tr>
+<td class="left top padr3">Hidrogen</td>
+<td class="left bot">5</td>
+</tr>
+
+<tr>
+<td class="left top padr3">Spermaceti oil 10 grains burnt in a lamp raised 30,000 grains of water</td>
+<td class="left bot">5</td>
+</tr>
+
+<tr>
+<td class="left top padr3">Tallow</td>
+<td class="left bot">5</td>
+</tr>
+
+<tr>
+<td class="left top padr3">Wax</td>
+<td class="left bot">5,75</td>
+</tr>
+
+<tr>
+<td class="left top padr3">Oil of turpentine</td>
+<td class="left bot">3</td>
+</tr>
+
+<tr>
+<td class="left top padr3">Spirit of wine</td>
+<td class="left bot">2</td>
+</tr>
+
+</table>
+
+</div>
+
+<p>In all processes of the arts where a moderate
+heat is wanted the gas-light flame will be found
+very advantageous&mdash;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<span class="pagenum"><a name="Page_114" id="Page_114">[114]</a></span>
+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.</p>
+
+<p>The great power of a gas-flame does not
+appear when we try small quantities of it, and<span class="pagenum"><a name="Page_115" id="Page_115">[115]</a></span>
+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.</p>
+
+<div class="figcenter"><a name="Plate3" id="Plate3"></a>
+<img src="images/illo131.jpg" alt="Gas lamps" width="600" height="367" />
+<p class="largeimg"><a href="images/lg131.jpg">Larger image</a> (252 kB)</p>
+</div>
+
+<p>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.</p>
+
+<p>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.</p>
+
+<p><a href="#Plate3"><span class="smcap">Plates</span> III.</a> <a href="#Plate4">IV.</a> and <a href="#Plate5">V.</a> exhibit such designs
+of different kinds of gas-lamps, chandeliers,
+lustres, candelabras, &amp;c. as are already in use
+in this Metropolis.</p>
+
+<p><a href="#Plate3"><span class="smcap">Plate</span> III. fig. 1</a>, represents a <em class="italic">Rod Lamp</em>.
+The gas passes through the rod <i>a</i>, to the Argand
+burner, which is surrounded by a cylindrical
+chimney, <i>c</i>, swelling out at the lower<span class="pagenum"><a name="Page_116" id="Page_116">[116]</a></span>
+extremity. The construction of the Argand
+burner we have mentioned already, <a href="#Page_78"><i>p.</i> 78</a>.</p>
+
+<p>In all the gas-light burners, constructed on
+Argand&#8217;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.</p>
+
+<p><a href="#Plate3">Fig. 2</a>. <em class="italic">A Rod Gas Lamp, with branches.</em>
+The gas passes through the hollow rod, <i>a</i>, and
+part of the hollow branch, <i>b</i>, to the burner of
+the lamp. The cylindrical shaped glass, <i>c</i>, exhibited
+in this figure, is not so well adapted for
+the compleat combustion of coal-gas, as the
+belly-shaped chimney, <i>c</i>, represented in<span class="pagenum"><a name="Page_117" id="Page_117">[117]</a></span> <a href="#Plate3">fig. 1,
+3, 5, 6</a>, 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,
+<a href="#Plate3">fig. 1</a>.</p>
+
+<p><a href="#Plate3">Fig. 3</a>. <em class="italic">A Bracket Lamp.</em> <i>a</i>, the tube
+which conveys the gas to the burner; <i>b</i>, the
+stop-cock of the tube.</p>
+
+<p><a href="#Plate3">Fig. 4</a>. <em class="italic">A Pendent Rod Lamp</em>; in which the
+gas is supposed to come from a pipe above,
+through the ceiling, into the pipe, <i>a</i>, to supply
+the burners. The tulip-shaped chimney, <i>b</i>,
+of this lamp, is likewise ill adapted for gas-light
+burners.</p>
+
+<p><a href="#Plate3">Fig. 5</a>. <em class="italic">A pendent double-bracket Lamp.</em>
+The gas passing through the perpendicular
+tube, <i>a</i>, into the brackets, <i>b</i> <i>b</i>; <i>c</i> shows the
+Argand burner.</p>
+
+<p><span class="pagenum"><a name="Page_118" id="Page_118">[118]</a></span></p>
+
+<p><a href="#Plate3">Fig. 6</a>. <em class="italic">A swing Bracket Lamp.</em> <i>a</i>, the
+gas-pipe with its stop-cock; <i>b</i>, a brass ball,
+communicating with the pipe, <i>a</i>; <i>c</i>, the conducting
+tube, ground air-tight into the ball,
+<i>b</i>, and communicating with the burner of the
+lamp, so as to allow it to have an horizontal
+motion.</p>
+
+<p><a href="#Plate3">Fig. 7</a>. Shews the construction of the ball
+<i>b</i>, and pipe, <i>c</i>, of the lamp, <a href="#Plate3">fig. 6</a>.</p>
+
+<p><a href="#Plate3">Fig. 8</a>. <em class="italic">A Swing Cockspur Lamp</em>, constructed
+upon the same plan as <a href="#Plate3">fig. 6</a>. These two
+lamps are very convenient for desks in counting-houses,
+&amp;c.</p>
+
+<p><a href="#Plate3">Fig. 9</a>. 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.</p>
+
+<p><a href="#Plate3">Fig. 10</a>. Section of the stop-cock, with ball
+and socket.</p>
+
+<p><a href="#Plate3">Fig. 11</a>. Shows the ball and socket, <a href="#Plate3">fig. 9</a>,
+in perspective.</p>
+
+<div class="figcenter"><a name="Plate4" id="Plate4"></a>
+<img src="images/illo137.jpg" alt="Gas lamps" width="600" height="343" />
+<p class="largeimg"><a href="images/lg137.jpg">Larger image</a> (205 kB)</p>
+</div>
+
+<p><a href="#Plate4"><span class="smcap">Plate</span> IV</a>,<a name="FNanchor_26" id="FNanchor_26"></a><a href="#Footnote_26" class="fnanchor">[26]</a> <a href="#Plate4">fig. 1</a>. <em class="italic">A Candelabrum</em>; the gas<span class="pagenum"><a name="Page_119" id="Page_119">[119]</a></span>
+pipe ascending from the floor of the apartment,
+through the column <i>a</i>, and terminating
+in the burner of the lamp.</p>
+
+<div class="footnote">
+
+<p><a name="Footnote_26" id="Footnote_26"></a><a href="#FNanchor_26"><span class="label">[26]</span></a> The gas-lamps exhibited in this plate, are employed
+in the library, counting-house, warehouse, and offices of
+Mr. <span class="smcap">Ackerman</span>, and, by whose permission, they are copied
+on this occasion.</p></div>
+
+<p><a href="#Plate4">Fig. 2</a>. <em class="italic">A fancy pendent Cockspur Lamp.</em>
+The gas being transmitted to the burners, <i>c</i> <i>c</i>,
+by means of the pipe, <i>a</i>.</p>
+
+<p><a href="#Plate4">Fig. 3</a>. <em class="italic">A Pedestal Argand Lamp.</em> <i>a</i>, the
+pipe and stop-cock, which transmits to, and
+shuts off the gas from the burner of the lamp.</p>
+
+<p><a href="#Plate4">Fig. 4</a>. <em class="italic">A Pedestal Cockspur Lamp.</em> <i>a</i>, the
+stop-cock and gas-pipe.</p>
+
+<p><a href="#Plate4">Fig. 5</a>. <em class="italic">A fancy bracket Cockspur Lamp</em>,
+intended merely to show that the coal-gas, as
+it passes to the burner, is perfectly devoid of
+colour, and invisible. <i>a</i> is a glass vessel furnished
+at its orifice with a brass cap, <i>c</i>, and
+perforated ball, out of which the gas-flame
+proceeds. <i>b</i>, the pipe which conveys the gas
+into the glass vessel, <i>a</i>.</p>
+
+<p><a href="#Plate4">Fig. 6</a>. <em class="italic">A Bracket Argand Lamp.</em> <i>a</i> and <i>b</i>,
+the gas pipe communicating with the burner.</p>
+
+<p><a href="#Plate4">Fig. 7 and 8</a>. <em class="italic">A Horizontal Bracket Lamp.</em>
+<i>a</i>, the gas pipe, supposed to be concealed
+in the ceiling. <i>b</i>, the communicating pipe,
+which, together with <i>c</i>, branches out at right
+angles at <i>d</i> <i>d</i>. <i>e</i> <i>e</i>, are the burners of the lamp.</p>
+
+<div class="figcenter"><a name="Plate5" id="Plate5"></a>
+<img src="images/illo140.jpg" alt="Gas lamps" width="600" height="355" />
+<p class="largeimg"><a href="images/lg140.jpg">Larger image</a> (286 kB)</p>
+</div>
+
+<p><span class="pagenum"><a name="Page_120" id="Page_120">[120]</a></span></p>
+
+<p><a href="#Plate5"><span class="smcap">Plate</span> V</a>. <a href="#Plate5">fig. 1</a>. <em class="italic">A Candelabrum</em>, into which
+the gas-pipe ascends from the floor of the
+apartment, the lateral branches communicating
+with the central tube.</p>
+
+<p><a href="#Plate5">Fig. 2</a>. <em class="italic">An Arabesque Chandelier.</em> The gas
+enters from the ceiling of the room into the
+rope-shaped pipe, <i>a</i>, from which it proceeds
+through one of the arched ribs, <i>b</i> <i>b</i>, into the
+horizontal hoop, or pipe, <i>c</i>.</p>
+
+<p><a href="#Plate5">Fig. 3</a>. <em class="italic">A Roman Chandelier.</em> The gas enters
+through the inflexible hollow chain, <i>a</i>, into
+the central tube, <i>b</i>, from whence the burners
+are supplied by the lateral branches, <i>c</i> <i>c</i>.</p>
+
+<p><a href="#Plate5">Fig. 4</a>. <em class="italic">A Gothic Chandelier.</em> The gas is
+transmitted to the burners through the rope, <i>a</i>,
+which includes a tube, and the communication
+with the burners is established through the
+lateral branches.</p>
+
+<p><a href="#Plate5">Fig. 5</a>. <em class="italic">A Pedestal Figure Lamp.</em> The gas is
+here made to pass by means of a pipe through
+the body of the figure into the lattice-work
+<em class="italic">plateau</em>, constructed of hollow and perforated
+brass tubes.</p>
+
+<p><a href="#Plate5">Fig. 6</a>. <em class="italic">A Pedestal Vase Lamp.</em> The gas-tube
+enters through one of the claw-feet of the
+altar-shaped pedestal, into the glass vase, <i>a</i>, at<span class="pagenum"><a name="Page_121" id="Page_121">[121]</a></span>
+the bottom of which it joins the tubes communicating
+with the metallic corn-ears, <i>b</i>, at the
+upper extremities of which it forms <em class="italic">jets de feu</em>.</p>
+
+<p><a href="#Plate5">Fig. 7</a>. <em class="italic">A Girandole.</em> The gas enters through
+the bracket, <i>a</i>, and is conveyed to the burners
+by the descending tubes, <i>b</i> <i>b</i>.</p>
+
+<p><a href="#Plate5">Fig. 8</a>. <em class="italic">A Candelabrum</em>, having a central
+pipe, through which the gas is conducted to
+the burner at the top.</p>
+
+<hr class="sect" />
+
+<h4><span class="fsize60">OTHER</span><br />
+PRODUCTS OBTAINABLE FROM COAL:<br />
+<span class="fsize60">NAMELY,</span><br />
+COKE, TAR, ESSENTIAL OIL, &amp;c.</h4>
+
+<p>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,
+&amp;c.</p>
+
+<p><em class="italic">Coke.</em>&mdash;The substance called coke, which
+constitutes the skeleton of the coal, or its carbonaceous
+base, is left behind in the retort, after<span class="pagenum"><a name="Page_122" id="Page_122">[122]</a></span>
+all the evaporable products have been expelled
+from the coal by heat.&mdash;See <a href="#Page_85">page 85</a>.</p>
+
+<p>It is sufficiently known, that coke is a more
+valuable fuel than the coal from which it is
+obtained.</p>
+
+<p>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.<a name="FNanchor_27" id="FNanchor_27"></a><a href="#Footnote_27" class="fnanchor">[27]</a> In the manufacture<span class="pagenum"><a name="Page_123" id="Page_123">[123]</a></span>
+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,&mdash;that
+specific for the <em class="italic">ennui</em> 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.</p>
+
+<div class="footnote">
+
+<p><a name="Footnote_27" id="Footnote_27"></a><a href="#FNanchor_27"><span class="label">[27]</span></a> The preparation of coke is as follows:&mdash;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
+faggots 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.</p></div>
+
+<p>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<span class="pagenum"><a name="Page_124" id="Page_124">[124]</a></span>
+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.</p>
+
+<p>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.</p>
+
+<p>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 <em class="italic">very intense</em>, 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<span class="pagenum"><a name="Page_125" id="Page_125">[125]</a></span>
+the fire, unless the bars of the grate be too
+close together.</p>
+
+<p>The relative effects of heat produced by
+coke and coal are as follows:&mdash;</p>
+
+<p>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.<a name="FNanchor_28" id="FNanchor_28"></a><a href="#Footnote_28" class="fnanchor">[28]</a></p>
+
+<div class="footnote">
+
+<p><a name="Footnote_28" id="Footnote_28"></a><a href="#FNanchor_28"><span class="label">[28]</span></a> 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,
+</p>
+<p>
+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.</p></div>
+
+<p><span class="pagenum"><a name="Page_126" id="Page_126">[126]</a></span></p>
+
+<p>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.</p>
+
+<p>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 <em class="italic">third more lime</em> at the <em class="italic">same time</em>.</p>
+
+<p>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.</p>
+
+<p><span class="pagenum"><a name="Page_127" id="Page_127">[127]</a></span></p>
+
+<p>The following account given by Mr. Davis,<a name="FNanchor_29" id="FNanchor_29"></a><a href="#Footnote_29" class="fnanchor">[29]</a>
+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.</p>
+
+<div class="footnote">
+
+<p><a name="Footnote_29" id="Footnote_29"></a><a href="#FNanchor_29"><span class="label">[29]</span></a> Philosophical Magazine, Vol. 33, p. 435.</p></div>
+
+<p>&#8220;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<span class="pagenum"><a name="Page_128" id="Page_128">[128]</a></span>
+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&#8217;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.</p>
+
+<p>&#8220;On applying coke instead of coal, the
+produce of lime may be increased to nearly 30<span class="pagenum"><a name="Page_129" id="Page_129">[129]</a></span>
+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 <em class="italic">less attendance</em> and <em class="italic">less labour</em>,
+and the whole saving, thus accomplished,
+amounts to more than 50 <em class="italic">per cent. on the
+lime-kiln</em>.</p>
+
+<p>&#8220;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&#8217;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.</p>
+
+<p>&#8220;If coke be applied instead of coal, the
+arches, or empty spaces in the clamp or pile,<span class="pagenum"><a name="Page_130" id="Page_130">[130]</a></span>
+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.</p>
+
+<p>&#8220;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.</p>
+
+<p>&#8220;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.&#8221;</p>
+
+<p>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,<span class="pagenum"><a name="Page_131" id="Page_131">[131]</a></span>
+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.</p>
+
+<p><em class="italic">Coal-tar</em>, <em class="italic">Oil</em>, and <em class="italic">Pitch</em>.&mdash;Another, valuable
+product obtainable from pit-coal, is coal-tar.<a name="FNanchor_30" id="FNanchor_30"></a><a href="#Footnote_30" class="fnanchor">[30]</a>
+This substance is deposited, in the purification
+of the coal-gas, in a separate vessel destined
+to receive it.</p>
+
+<div class="footnote">
+
+<p><a name="Footnote_30" id="Footnote_30"></a><a href="#FNanchor_30"><span class="label">[30]</span></a> 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.</p></div>
+
+<p>The coal-tar is so called from its resembling
+common tar in its appearance, and most of its
+qualities.</p>
+
+<p>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<span class="pagenum"><a name="Page_132" id="Page_132">[132]</a></span>
+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.</p>
+
+<p>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.</p>
+
+<p>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 <a href="#Page_94">page 94</a>.</p>
+
+<p>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.</p>
+
+<p>To render the tar fit for use, it requires to
+be evaporated to give it a sufficient consistence.<span class="pagenum"><a name="Page_133" id="Page_133">[133]</a></span>
+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.</p>
+
+<p>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.</p>
+
+<p>Two hundred pounds of tar produce, upon
+an average, fifty-three pounds of essential oil.</p>
+
+<p>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<span class="pagenum"><a name="Page_134" id="Page_134">[134]</a></span>
+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.</p>
+
+<div class="figcenter">
+<p class="caption"><i>Kettle for boiling Tar.</i></p>
+<img src="images/illo155.png" alt="" width="350" height="205" />
+</div>
+
+<p>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 <em class="italic">asphaltum</em>.</p>
+
+<p><em class="italic">Ammoniacal Fluid.</em>&mdash;The properties of the
+ammoniacal liquor, which accompanies the tar,<span class="pagenum"><a name="Page_135" id="Page_135">[135]</a></span>
+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.&mdash;Such
+are the products obtainable from coal.</p>
+
+<p>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&mdash;the
+adoption of experimental research&mdash;the
+substitution of the doctrine of gravitation
+instead of that of vortices, and the rejection
+of phlogiston by modern chemists, are<span class="pagenum"><a name="Page_136" id="Page_136">[136]</a></span>
+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&mdash;the new rudiments
+of science&mdash;the new stile&mdash;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.</p>
+
+<p>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 <em class="italic">fashion</em>.</p>
+
+<p>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,<span class="pagenum"><a name="Page_137" id="Page_137">[137]</a></span>
+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.</p>
+
+<p>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.</p>
+
+<p>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<span class="pagenum"><a name="Page_138" id="Page_138">[138]</a></span>
+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.</p>
+
+<p>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&mdash;that it tends to drive them
+out of the system of beneficial employment&mdash;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&mdash;a man and a horse.
+I must invariably prefer the latter, and leave
+the former to starve. Two other beings&mdash;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<span class="pagenum"><a name="Page_139" id="Page_139">[139]</a></span>
+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.</p>
+
+<p>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.</p>
+
+<p><span class="pagenum"><a name="Page_140" id="Page_140">[140]</a></span></p>
+
+<p>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.</p>
+
+<p>But let us return to the subject.&mdash;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.</p>
+
+<p>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<span class="pagenum"><a name="Page_141" id="Page_141">[141]</a></span>
+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.</p>
+
+<p>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.</p>
+
+<p>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&mdash;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.</p>
+
+<p>If any additional want were wanted for the<span class="pagenum"><a name="Page_142" id="Page_142">[142]</a></span>
+coke it will readily be found in the continental
+market; coke being much better suited than
+coal to the habits of most European nations.</p>
+
+<p>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.</p>
+
+<p>It is worthy observation, that the annual
+importation of coal into this Metropolis, is
+above one million and eighty-eight thousand
+chaldrons.<a name="FNanchor_31" id="FNanchor_31"></a><a href="#Footnote_31" class="fnanchor">[31]</a></p>
+
+<div class="footnote">
+
+<p><a name="Footnote_31" id="Footnote_31"></a><a href="#FNanchor_31"><span class="label">[31]</span></a> 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,
+</p>
+<p>
+<em class="italic">1st</em>. 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.
+</p>
+<p>
+<em class="italic">2dly</em>. That this seam, on an average, is at least four feet
+and a half thick.
+</p>
+<p>
+<em class="italic">3dly</em>, That 1-6th part of the above extent is sufficient
+for pillars to support the roofs of the mines, &amp;c.
+</p>
+<p>
+And, <em class="italic">4thly</em>, It appears, by experiments, that a cubic
+yard of coal weighs 1 ton, or 20 cwt.
+</p>
+
+<table summary="Table footnote 31">
+
+<tr>
+<td>&nbsp;</td>
+<td class="center fsize80">London Chaldrons</td>
+</tr>
+
+<tr>
+<td class="just top padr3">The total consumption of coal from the rivers Tyne and Wear known from the register to be</td>
+<td class="right bot">2,300,000</td>
+</tr>
+
+<tr>
+<td class="just top padr3">The number of tons in the above quantity taking the London chaldron at 27 cwt. is</td>
+<td class="right bot">3,100,000</td>
+</tr>
+
+<tr>
+<td colspan="2" class="just top">Now a ton weight of coal is estimated to occupy in the earth the space of one cubic yard.</td>
+</tr>
+
+<tr>
+<td class="just top padr3">The number of cubic yards in the square mile is</td>
+<td class="right bot">3,097,600</td>
+</tr>
+
+<tr>
+<td class="just top padr3">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</td>
+<td class="right bot">1,548,800</td>
+</tr>
+
+<tr>
+<td class="just top padr3">And hence the square mile of the beds or seams of coal we are describing contains, of cubic yards and tons of coal</td>
+<td class="right bot">4,645,000</td>
+</tr>
+
+<tr>
+<td class="just top padr3">A deduction of 1-6th for pillars to support the mine, &amp;c.</td>
+<td class="right bot">800,000</td>
+</tr>
+
+<tr>
+<td class="just top padr3">The number of tons per square mile</td>
+<td class="right bot">5,445,000</td>
+</tr>
+
+</table>
+
+<p>
+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.</p></div>
+
+<p><span class="pagenum"><a name="Page_143" id="Page_143">[143]</a></span></p>
+
+<p>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<span class="pagenum"><a name="Page_144" id="Page_144">[144]</a></span>
+illumination. But there are two reasons why
+this should have less place, because we find,
+in Mr. Murdoch&#8217;s statement, <a href="#Page_69">page 69</a>, 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.<a name="FNanchor_32" id="FNanchor_32"></a><a href="#Footnote_32" class="fnanchor">[32]</a></p>
+
+<div class="footnote">
+
+<p><a name="Footnote_32" id="Footnote_32"></a><a href="#FNanchor_32"><span class="label">[32]</span></a> See, also, Mr. Ackermann&#8217;s statement, <a href="#Page_71">page 71</a>.</p></div>
+
+<p><em class="italic">2dly</em>, The coal, by yielding the gas and other
+products,&mdash;namely, tar, pitch, ammoniacal liquor,
+&amp;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,<span class="pagenum"><a name="Page_145" id="Page_145">[145]</a></span>
+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.</p>
+
+<p>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<span class="pagenum"><a name="Page_146" id="Page_146">[146]</a></span>
+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.</p>
+
+<p>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.</p>
+
+<p>From experiments, made by Mr. <span class="smcap">Clegg</span>, on
+the effects produced by a number of gas-lights,
+of a certain intensity, there is reason to believe<span class="pagenum"><a name="Page_147" id="Page_147">[147]</a></span>
+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.</p>
+
+<p>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.&mdash;Hence, as already
+stated, the lighting of the parish, or street-lamps
+only, without lighting shops or houses,
+can never be accomplished with economy.</p>
+
+<p>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<span class="pagenum"><a name="Page_148" id="Page_148">[148]</a></span>
+coals, called slack, which pass through the
+screen at the pit&#8217;s mouth, and which cannot
+be brought into the market&mdash;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,<a name="FNanchor_33" id="FNanchor_33"></a><a href="#Footnote_33" class="fnanchor">[33]</a> which is a practice commonly<span class="pagenum"><a name="Page_149" id="Page_149">[149]</a></span>
+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<span class="pagenum"><a name="Page_150" id="Page_150">[150]</a></span>
+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.</p>
+
+<div class="footnote">
+
+<p><a name="Footnote_33" id="Footnote_33"></a><a href="#FNanchor_33"><span class="label">[33]</span></a> 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.
+</p>
+<p>
+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.
+</p>
+<p>
+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.
+</p>
+<p>
+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.
+</p>
+<p>
+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.&mdash;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.</p></div>
+
+<p>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,<span class="pagenum"><a name="Page_151" id="Page_151">[151]</a></span>
+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.</p>
+
+<p>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<span class="pagenum"><a name="Page_152" id="Page_152">[152]</a></span>
+to stir a fire without judgment; to prevent
+which he lays down the following rules:&mdash;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.</p>
+
+<p>There is one subject more on which it is
+necessary to speak.&mdash;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.</p>
+
+<p>Those who are familiar with the subject
+will readily allow, that there is no more risk<span class="pagenum"><a name="Page_153" id="Page_153">[153]</a></span>
+in the action of a gas-light machinery, properly
+constructed, than there is in the action
+of a steam-engine, built on just principles.</p>
+
+<p>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.</p>
+
+<p>No part of the machinery is liable to be out
+of order,&mdash;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<span class="pagenum"><a name="Page_154" id="Page_154">[154]</a></span>
+as we depend on the light to be obtained from
+a certain number of candles or oil-lamps.</p>
+
+<p>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.</p>
+
+<p>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<span class="pagenum"><a name="Page_155" id="Page_155">[155]</a></span>
+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.</p>
+
+<p>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.</p>
+
+<p>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<span class="pagenum"><a name="Page_156" id="Page_156">[156]</a></span>
+body, as has been stated, <a href="#Page_98">page 98</a>, 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, &amp;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<span class="pagenum"><a name="Page_157" id="Page_157">[157]</a></span>
+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.</p>
+
+<p><span class="pagenum"><a name="Page_158" id="Page_158">[158]</a></span></p>
+
+<div class="london_b"><a name="FigLondon" id="FigLondon"></a>
+<div class="ill_b">
+
+<p class="fsize80 nowrap" style="padding-left: .5em; padding-top: .75em;">Main pipe, leading from the Gas-light station or
+apparatus,<br />situated in Brick Lane, near Old St.<a name="FNanchor_34" id="FNanchor_34"></a><a href="#Footnote_34" class="fnanchor">[34]</a></p>
+
+<p class="fsize80 left" style="padding-left: 37em; padding-top: 3em;">Main pipe, leading from the gaslight apparatus,
+or station, at Norton Falgate.<a name="FNanchor_35" id="FNanchor_35"></a><a href="#Footnote_35" class="fnanchor">[35]</a></p>
+
+<p class="fsize80 left" style="padding-left: .5em; padding-top: 12.5em;">Main pipe, leading from the gaslight apparatus,
+or station,<br />in Westminster.<a name="FNanchor_36" id="FNanchor_36"></a><a href="#Footnote_36" class="fnanchor">[36]</a></p>
+
+</div><!--ill_b-->
+
+<div class="footnote">
+
+<p><a name="Footnote_34" id="Footnote_34"></a><a href="#FNanchor_34"><span class="label">[34]</span></a> <em class="italic">The gasometer at this place is equal in capacity to 22000 cubic feet.</em></p>
+
+<p><a name="Footnote_35" id="Footnote_35"></a><a href="#FNanchor_35"><span class="label">[35]</span></a> <em class="italic">The capacity of the gasometer here is equal to 15928 cubic feet.</em></p>
+
+<p><a name="Footnote_36" id="Footnote_36"></a><a href="#FNanchor_36"><span class="label">[36]</span></a> <em class="italic">At this station the gasometer is equal in capacity to 14808 cubic feet.</em></p></div>
+
+</div><!--london_b-->
+
+<div class="london_e">
+<div class="ill_e">
+<img src="images/illo_e179.png" alt="Pipe network" width="500" height="385" />
+</div><!--ill_e-->
+
+<div class="footnote">
+
+<p><span class="label">*</span> <em class="italic">The gasometer at this place is equal in capacity to 22000 cubic feet.</em></p>
+
+<p><span class="label">&#8224;</span> <em class="italic">The capacity of the gasometer here is equal to 15928 cubic feet.</em></p>
+
+<p><span class="label">&#8225;</span> <em class="italic">At this station the gasometer is equal in capacity to 14808 cubic feet.</em></p></div>
+
+</div><!--london_e-->
+
+<p>The <a href="#FigLondon">black lines</a> 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, <em class="italic">Pall Mall</em>, should break, it is evident,
+on mere inspection, that the gas which is<span class="pagenum"><a name="Page_159" id="Page_159">[159]</a></span>
+passing through the main in the <em class="italic">Strand</em>, and
+which is also connected with the main in the
+<em class="italic">Haymarket</em>, <em class="italic">Piccadilly</em>, and <em class="italic">Coventry Street</em>,
+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.</p>
+
+<p>Further, let us suppose a main pipe should
+break in <em class="italic">Piccadilly</em>; in that case, the valve
+being shut on each side of the fracture, the gas
+would be supplied from the mains in the <em class="italic">Haymarket</em>
+and <em class="italic">St. James&#8217;s Street</em>. 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<span class="pagenum"><a name="Page_160" id="Page_160">[160]</a></span>
+streets.<a name="FNanchor_37" id="FNanchor_37"></a><a href="#Footnote_37" class="fnanchor">[37]</a> 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.</p>
+
+<div class="footnote">
+
+<p><a name="Footnote_37" id="Footnote_37"></a><a href="#FNanchor_37"><span class="label">[37]</span></a> As shown in the <a href="#FigLondon">sketch</a>.</p></div>
+
+<p>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<span class="pagenum"><a name="Page_161" id="Page_161">[161]</a></span>
+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.<a name="FNanchor_38" id="FNanchor_38"></a><a href="#Footnote_38" class="fnanchor">[38]</a> 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,<span class="pagenum"><a name="Page_162" id="Page_162">[162]</a></span>
+as well as political recommendations,
+for the adoption of the new lights in all manufactories
+where work is done by candle-light.</p>
+
+<div class="footnote">
+
+<p><a name="Footnote_38" id="Footnote_38"></a><a href="#FNanchor_38"><span class="label">[38]</span></a> Since the preceding pages have been printed, I have
+seen a <em class="italic">self-extinguishing gas-lamp</em>, invented by Mr. <span class="smcap">Clegg</span>.
+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. <span class="smcap">Clegg</span> 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.</p></div>
+
+<p>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<span class="pagenum"><a name="Page_163" id="Page_163">[163]</a></span>
+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.</p>
+
+<p>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.</p>
+
+<hr class="sect" />
+
+<p><span class="pagenum"><a name="Page_164" id="Page_164">[164]</a></span></p>
+
+<h3 class="noblank"><b>TABULAR VIEW,</b></h3>
+
+<p class="center fsize80">EXHIBITING</p>
+
+<p>The quantity of <span class="smcap">Gas</span>, <span class="smcap">Coke</span>, <span class="smcap">Tar</span>, <span class="smcap">Pitch</span>, <span class="smcap">Essential Oil</span>, and <span class="smcap">Ammoniacal Liquor</span>, obtainable from a given
+quantity of <span class="smcap">Coal</span>; 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.</p>
+
+<table class="nowrap esmallest" summary="Table page 164">
+
+<tr>
+<th colspan="3">&nbsp;</th>
+<th colspan="14" class="center padl1 padr1 br"><em class="italic">Cost of Coal.</em></th>
+<th colspan="8" class="center padl1 padr1 br"><em class="italic">Weight of Coal.</em></th>
+<th colspan="6" class="center padl1 padr1"><em class="italic">Produce of Gas, in cubic feet.</em></th>
+<td rowspan="8" class="bt br bb narrow">&nbsp;</td>
+<td rowspan="8" class="left padl0 narrow">-</td>
+<td rowspan="8" class="left padl1 padr1 br wrappable"><a name="FNanchor_39" id="FNanchor_39"></a><a href="#Footnote_39" class="fnanchor">[39]</a>Equal to as many tallow candles, 12 in the pound, burning two hours; or to</td>
+<th colspan="3" class="center padl1 padr1"><em class="italic">Candles.</em></th>
+</tr>
+
+<tr>
+<th colspan="3">&nbsp;</th>
+<th colspan="4" class="center padl1 padr1">Mini-<br />mum.</th>
+<th>&nbsp;</th>
+<th colspan="4" class="center padl1 padr1">Maxi-<br />mum.</th>
+<th>&nbsp;</th>
+<th colspan="4" class="center padl1 padr1 br">Aver-<br />age.</th>
+<th colspan="2" class="center padl1 padr1">Min.</th>
+<th>&nbsp;</th>
+<th colspan="2" class="center padl1 padr1">Max.</th>
+<th>&nbsp;</th>
+<th colspan="2" class="center padl1 padr1 br">Aver.</th>
+<th class="center padl1 padr1">Min.</th>
+<th>&nbsp;</th>
+<th class="center padl1 padr1">Max.</th>
+<th>&nbsp;</th>
+<th colspan="2" class="center padl1 padr1">Aver.</th>
+<td class="right padl1 padr1">9,516<br />8,651</td>
+<td class="right padr1">11<br />10</td>
+<td class="left">to the pound.<br /><span class="noshow">to th</span>do.</td>
+</tr>
+
+<tr>
+<td class="left">One Chal.<br />of Coal,<br />from 25<br />to 28 cwt.</td>
+<td class="bt br bb narrow">&nbsp;</td>
+<td class="left padl0">-</td>
+<td class="right padl1 padr0">40</td>
+<td class="left padl0 padr1"><i>s</i></td>
+<td colspan="2">&nbsp;</td>
+<td class="center">to</td>
+<td class="right padl1 padr0">60</td>
+<td class="left padl0 padr1"><i>s</i></td>
+<td colspan="2">&nbsp;</td>
+<td class="center">&mdash;</td>
+<td class="right padl1 padr0">50</td>
+<td class="left padl0 padr1"><i>s</i></td>
+<td colspan="2" class="br">&nbsp;</td>
+<td class="right padl1 padr0">2,800</td>
+<td>&nbsp;</td>
+<td class="center">to</td>
+<td class="right padl1 padr0">3,136</td>
+<td>&nbsp;</td>
+<td class="center">&mdash;</td>
+<td class="right padl1 padr0">2,968</td>
+<td class="br">&nbsp;</td>
+<td class="right padl1 padr1">8,906</td>
+<td class="center">to</td>
+<td class="right padl1 padr1">11,872</td>
+<td class="center">&mdash;</td>
+<td class="right padl1 padr0">10,388</td>
+<td class="left padl0 padr0"><a href="#Footnote_39" class="fnanchor">[39]</a></td>
+<td class="right padl1 padr1">7,786<br />6,921<br />6,556<br />5,194</td>
+<td class="right padr1">10<br />9<br />8<br />7</td>
+<td class="left"><span class="noshow">to th</span>do.<br /><span class="noshow">to th</span>do.<br /><span class="noshow">to th</span>do.<br /><span class="noshow">to th</span>do.</td>
+</tr>
+
+<tr>
+<td colspan="3" class="left">One Ton</td>
+<td class="right padl1 padr0">30</td>
+<td class="left padl0 padr1"><i>s</i></td>
+<td colspan="2">&nbsp;</td>
+<td class="center">to</td>
+<td class="right padl1 padr0">48</td>
+<td class="left padl0 padr1"><i>s</i></td>
+<td colspan="2">&nbsp;</td>
+<td class="center">&mdash;</td>
+<td class="right padl1 padr0">38</td>
+<td class="left padl0 padr1"><i>s</i></td>
+<td class="right padr0">6</td>
+<td class="left padl0 padr1 br"><i>d</i></td>
+<td colspan="6">&nbsp;</td>
+<td class="right padl1 padr0">2,240</td>
+<td class="br">&nbsp;</td>
+<td class="right padl1 padr1">6,720</td>
+<td class="center">to</td>
+<td class="right padl1 padr1">8,960</td>
+<td class="center">&mdash;</td>
+<td class="right padl1 padr0">7,840</td>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">4,325</td>
+<td class="right padr1">5</td>
+<td class="left"><span class="noshow">to th</span>do.</td>
+</tr>
+
+<tr>
+<td colspan="3" class="left">One Sack</td>
+<td class="right padl1 padr0">3</td>
+<td class="left padl0 padr1"><i>s</i></td>
+<td class="right padr0">4</td>
+<td class="left padl0 padr1"><i>d</i></td>
+<td class="center">to</td>
+<td class="right padl1 padr0">5</td>
+<td class="left padl0 padr1"><i>s</i></td>
+<td colspan="2">&nbsp;</td>
+<td class="center">&mdash;</td>
+<td class="right padl1 padr0">4</td>
+<td class="left padl0 padr1"><i>s</i></td>
+<td class="right padr0">2</td>
+<td class="left padl0 padr1 br"><i>d</i></td>
+<td class="right padl1 padr0">233</td>
+<td>&nbsp;</td>
+<td class="center">to</td>
+<td class="right padr0">261</td>
+<td>&nbsp;</td>
+<td class="center">&mdash;</td>
+<td class="right padl1 padr0">247</td>
+<td class="br">&nbsp;</td>
+<td class="right padl1 padr1">741</td>
+<td class="center">to</td>
+<td class="right padl1 padr1">988</td>
+<td class="center">&mdash;</td>
+<td class="right padl1 padr0">814</td>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">3,463</td>
+<td class="right padr1">4</td>
+<td class="left"><span class="noshow">to th</span>do.</td>
+</tr>
+
+<tr>
+<td colspan="3" class="left">One Bushel</td>
+<td class="right padl1 padr0">1</td>
+<td class="left padl0 padr1"><i>s</i></td>
+<td class="right padr0">2</td>
+<td class="left padl0 padr1"><i>d</i></td>
+<td class="center">to</td>
+<td class="right padl1 padr0">1</td>
+<td class="left padl0 padr1"><i>s</i></td>
+<td class="right padr0">8</td>
+<td class="left padl0 padr1"><i>d</i></td>
+<td class="center">&mdash;</td>
+<td class="right padl1 padr0">1</td>
+<td class="left padl0 padr1"><i>s</i></td>
+<td class="right padr0">5</td>
+<td class="left padl0 padr1 br"><i>d</i></td>
+<td class="right padl1 padr0">78</td>
+<td>&nbsp;</td>
+<td class="center">to</td>
+<td class="right padl1 padr0">87</td>
+<td>&nbsp;</td>
+<td class="center">&mdash;</td>
+<td class="right padl1 padr0">82</td>
+<td class="left padl0 padr1 br"><sup>1</sup>&#8260;<sub>2</sub></td>
+<td class="right padl1 padr1">247</td>
+<td class="center">to</td>
+<td class="right padl1 padr1">330</td>
+<td class="center">&mdash;</td>
+<td class="right padl1 padr0">290</td>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">2,595</td>
+<td class="right padr1">3</td>
+<td class="left"><span class="noshow">to th</span>do.</td>
+</tr>
+
+<tr>
+<td colspan="3" class="left">One Peck</td>
+<td colspan="2">&nbsp;</td>
+<td class="right padl1 padr0">3</td>
+<td class="left padl0 padr1"><sup>1</sup>&#8260;<sub>2</sub></td>
+<td class="center">to</td>
+<td colspan="2">&nbsp;</td>
+<td class="right padr0">5</td>
+<td class="left padl0 padr1"><i>d</i></td>
+<td class="center">&mdash;</td>
+<td colspan="2">&nbsp;</td>
+<td class="right padl1 padr0">4</td>
+<td class="left padl0 padr1 br"><sup>1</sup>&#8260;<sub>4</sub></td>
+<td class="right padl1 padr0">19</td>
+<td class="left padl0 padr1"><sup>1</sup>&#8260;<sub>2</sub></td>
+<td class="center">to</td>
+<td class="right padl1 padr0">21</td>
+<td class="left padl0 padr1"><sup>1</sup>&#8260;<sub>4</sub></td>
+<td class="center">&mdash;</td>
+<td class="right padl1 padr0">20</td>
+<td class="left padl0 padr1 br"><sup>1</sup>&#8260;<sub>4</sub></td>
+<td class="right padl1 padr1">61</td>
+<td class="center">to</td>
+<td class="right padl1 padr1">82</td>
+<td class="center">&mdash;</td>
+<td class="right padl1 padr0">71</td>
+<td class="left padl0 padr1"><sup>1</sup>&#8260;<sub>2</sub></td>
+<td class="right padl1 padr1">1,730</td>
+<td class="right padr1">2</td>
+<td class="left"><span class="noshow">to th</span>do.</td>
+</tr>
+
+<tr>
+<td colspan="3" class="left">One Pound</td>
+<td colspan="13">&nbsp;</td>
+<td class="left padl0 padr1 br"><sup>1</sup>&#8260;<sub>4</sub></td>
+<td colspan="6">&nbsp;</td>
+<td class="right padl1 padr0">1</td>
+<td class="br">&nbsp;</td>
+<td class="right padl1 padr1">3</td>
+<td class="center">to</td>
+<td class="right padl1 padr1">4</td>
+<td class="center">&mdash;</td>
+<td class="right padl1 padr0">3</td>
+<td class="left padl0 padr1"><sup>1</sup>&#8260;<sub>2</sub></td>
+<td class="right padl1 padr1">866</td>
+<td class="right padr1">1</td>
+<td class="left"><span class="noshow">to th</span>do.</td>
+</tr>
+
+<tr>
+<td class="blankabove">&nbsp;</td>
+<td colspan="36" class="just wrappable blankabove"><span class="smcap">Coke.</span>&mdash;One chaldron of coal, from 25 to 28 cwt. gives 1<sup>1</sup>&#8260;<sub>4</sub> to 1&frac12; chaldron of Coke.</td>
+</tr>
+
+<tr>
+<td>&nbsp;</td>
+<td colspan="36" class="just wrappable"><span class="smcap">Tar.</span>&mdash;One chaldron of coal, from 25 to 28 cwt. gives from 150 to 180lb. of Tar,<a href="#Footnote_39" class="fnanchor">[39]</a> or 15 to 18 ale gallons, 10lb. each.</td>
+</tr>
+
+<tr>
+<td>&nbsp;</td>
+<td colspan="36" class="just wrappable"><span class="smcap">Ammoniacal Liquor.</span>&mdash;One chaldron of coal, gives from 220 to 240lb. of Ammoniacal Liquor, or 22 to 24 ale gallons.</td>
+</tr>
+
+</table>
+
+<div class="footnote">
+
+<p><a name="Footnote_39" id="Footnote_39"></a><a href="#FNanchor_39"><span class="label">[39]</span></a>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.</p></div>
+
+<hr class="sect" />
+
+<p><span class="pagenum"><a name="Page_165" id="Page_165">[165]</a></span></p>
+
+<p class="center"><i>Tabular View, exhibiting the illuminating power of Coal-Gas, compared with the illuminating power
+of Tallow Candles of different sizes.</i></p>
+
+<table class="nowrap" summary="Table page 165">
+
+<tr>
+<th colspan="11" class="center padl1 padr1">One chaldron of Coal produces, according to weight and quality,</th>
+</tr>
+
+<tr class="fsize80">
+<th colspan="6">&nbsp;</th>
+<th class="center padl1 padr1">Burning.</th>
+<th class="center padl1 padr1">Candles.</th>
+<th class="right padl1 padr1">12 to 1lb.</th>
+<th>&nbsp;</th>
+<th class="right padl1 padr1">6 to 1lb.</th>
+</tr>
+
+<tr>
+<th colspan="4" class="center padl1 padr1 fsize80">Cubic feet of Gas.</th>
+<th class="center padl1 padr1 fsize80">Average.</th>
+<td class="right padr1">1</td>
+<td class="center">hour</td>
+<td class="center padl1 padr1">=</td>
+<td class="right padr1">21,000</td>
+<td class="center padl1 padr1">=</td>
+<td class="right padl1 padr1">10,500</td>
+</tr>
+
+<tr>
+<td class="left">From</td>
+<td class="right padl1 padr1">9,000</td>
+<td class="center">to</td>
+<td class="right padl1 padr1">12,000</td>
+<td class="right padl1 padr1">10,500</td>
+<td class="right padl1 padr1">2</td>
+<td class="center">hours</td>
+<td class="center">=</td>
+<td class="right padl1 padr1">10,500</td>
+<td class="center">=</td>
+<td class="right padl1 padr1">5,250</td>
+</tr>
+
+<tr>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">6,000</td>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">8,000</td>
+<td class="right padl1 padr1">7,000</td>
+<td class="right padl1 padr1">3</td>
+<td class="center">ditto</td>
+<td class="center">=</td>
+<td class="right padl1 padr1">7,000</td>
+<td class="center">=</td>
+<td class="right padl1 padr1">3,500</td>
+</tr>
+
+<tr>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">4,500</td>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">6,000</td>
+<td class="right padl1 padr1">5,250</td>
+<td class="right padl1 padr1">4</td>
+<td class="center">ditto</td>
+<td class="center">=</td>
+<td class="right padl1 padr1">5,250</td>
+<td class="center">=</td>
+<td class="right padl1 padr1">2,625</td>
+</tr>
+
+<tr>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">3,600</td>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">4,800</td>
+<td class="right padl1 padr1">4,400</td>
+<td class="right padl1 padr1">5</td>
+<td class="center">ditto</td>
+<td class="center">=</td>
+<td class="right padl1 padr1">4,400</td>
+<td class="center">=</td>
+<td class="right padl1 padr1">2,200</td>
+</tr>
+
+<tr>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">3,000</td>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">4,000</td>
+<td class="right padl1 padr1">3,500</td>
+<td class="right padl1 padr1">6</td>
+<td class="center">ditto</td>
+<td class="center">=</td>
+<td class="right padl1 padr1">3,500</td>
+<td class="center">=</td>
+<td class="right padl1 padr1">1,750</td>
+</tr>
+
+<tr>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">2,571</td>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">3,428</td>
+<td class="right padl1 padr1">3,005</td>
+<td class="right padl1 padr1">7</td>
+<td class="center">ditto</td>
+<td class="center">=</td>
+<td class="right padl1 padr1">3,005</td>
+<td class="center">=</td>
+<td class="right padl1 padr1">1,502</td>
+</tr>
+
+<tr>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">2,250</td>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">3,000</td>
+<td class="right padl1 padr1">2,625</td>
+<td class="right padl1 padr1">8</td>
+<td class="center">ditto</td>
+<td class="center">=</td>
+<td class="right padl1 padr1">2,625</td>
+<td class="center">=</td>
+<td class="right padl1 padr1">1,312</td>
+</tr>
+
+<tr>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">2,000</td>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">2,666</td>
+<td class="right padl1 padr1">2,333</td>
+<td class="right padl1 padr1">9</td>
+<td class="center">ditto</td>
+<td class="center">=</td>
+<td class="right padl1 padr1">2,333</td>
+<td class="center">=</td>
+<td class="right padl1 padr1">1,166</td>
+</tr>
+
+<tr>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">1,800</td>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">2,100</td>
+<td class="right padl1 padr1">2,100</td>
+<td class="right padl1 padr1">10</td>
+<td class="center">ditto</td>
+<td class="center">=</td>
+<td class="right padl1 padr1">2,100</td>
+<td class="center">=</td>
+<td class="right padl1 padr1">1,050</td>
+</tr>
+
+<tr>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">1,636</td>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">2,191</td>
+<td class="right padl1 padr1">1,913</td>
+<td class="right padl1 padr1">11</td>
+<td class="center">ditto</td>
+<td class="center">=</td>
+<td class="right padl1 padr1">1,913</td>
+<td class="center">=</td>
+<td class="right padl1 padr1">956</td>
+</tr>
+
+<tr>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">1,500</td>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">2,000</td>
+<td class="right padl1 padr1">1,750</td>
+<td class="right padl1 padr1">12</td>
+<td class="center">ditto</td>
+<td class="center">=</td>
+<td class="right padl1 padr1">1,750</td>
+<td class="center">=</td>
+<td class="right padl1 padr1">875</td>
+</tr>
+
+<tr>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">1,384</td>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">1,846</td>
+<td class="right padl1 padr1">1,615</td>
+<td class="right padl1 padr1">13</td>
+<td class="center">ditto</td>
+<td class="center">=</td>
+<td class="right padl1 padr1">1,615</td>
+<td class="center">=</td>
+<td class="right padl1 padr1">807</td>
+</tr>
+
+<tr>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">1,285</td>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">1,714</td>
+<td class="right padl1 padr1">1,499</td>
+<td class="right padl1 padr1">14</td>
+<td class="center">ditto</td>
+<td class="center">=</td>
+<td class="right padl1 padr1">1,499</td>
+<td class="center">=</td>
+<td class="right padl1 padr1">749</td>
+</tr>
+
+<tr>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">1,200</td>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">1,600</td>
+<td class="right padl1 padr1">1,400</td>
+<td class="right padl1 padr1">15</td>
+<td class="center">ditto</td>
+<td class="center">=</td>
+<td class="right padl1 padr1">1,400</td>
+<td class="center">=</td>
+<td class="right padl1 padr1">700</td>
+</tr>
+
+<tr>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">1,125</td>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">1,500</td>
+<td class="right padl1 padr1">1,312</td>
+<td class="right padl1 padr1">16</td>
+<td class="center">ditto</td>
+<td class="center">=</td>
+<td class="right padl1 padr1">1,312</td>
+<td class="center">=</td>
+<td class="right padl1 padr1">656</td>
+</tr>
+
+<tr>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">1,058</td>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">1,111</td>
+<td class="right padl1 padr1">1,234</td>
+<td class="right padl1 padr1">17</td>
+<td class="center">ditto</td>
+<td class="center">=</td>
+<td class="right padl1 padr1">1,234</td>
+<td class="center">=</td>
+<td class="right padl1 padr1">617</td>
+</tr>
+
+<tr>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">1,000</td>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">1,333</td>
+<td class="right padl1 padr1">1,166</td>
+<td class="right padl1 padr1">18</td>
+<td class="center">ditto</td>
+<td class="center">=</td>
+<td class="right padl1 padr1">1,166</td>
+<td class="center">=</td>
+<td class="right padl1 padr1">583</td>
+</tr>
+
+<tr>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">947</td>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">1,263</td>
+<td class="right padl1 padr1">1,105</td>
+<td class="right padl1 padr1">19</td>
+<td class="center">ditto</td>
+<td class="center">=</td>
+<td class="right padl1 padr1">1,105</td>
+<td class="center">=</td>
+<td class="right padl1 padr1">552</td>
+</tr>
+
+<tr>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">900</td>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">1,200</td>
+<td class="right padl1 padr1">1,050</td>
+<td class="right padl1 padr1">20</td>
+<td class="center">ditto</td>
+<td class="center">=</td>
+<td class="right padl1 padr1">1,050</td>
+<td class="center">=</td>
+<td class="right padl1 padr1">525</td>
+</tr>
+
+<tr>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">857</td>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">1,143</td>
+<td class="right padl1 padr1">1,000</td>
+<td class="right padl1 padr1">21</td>
+<td class="center">ditto</td>
+<td class="center">=</td>
+<td class="right padl1 padr1">1,000</td>
+<td class="center">=</td>
+<td class="right padl1 padr1">500</td>
+</tr>
+
+<tr>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">818</td>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">1,095</td>
+<td class="right padl1 padr1">956</td>
+<td class="right padl1 padr1">22</td>
+<td class="center">ditto</td>
+<td class="center">=</td>
+<td class="right padl1 padr1">956</td>
+<td class="center">=</td>
+<td class="right padl1 padr1">478</td>
+</tr>
+
+<tr>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">783</td>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">1,044</td>
+<td class="right padl1 padr1">913</td>
+<td class="right padl1 padr1">23</td>
+<td class="center">ditto</td>
+<td class="center">=</td>
+<td class="right padl1 padr1">913</td>
+<td class="center">=</td>
+<td class="right padl1 padr1">456</td>
+</tr>
+
+<tr>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">750</td>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">1,000</td>
+<td class="right padl1 padr1">875</td>
+<td class="right padl1 padr1">21</td>
+<td class="center">ditto</td>
+<td class="center">=</td>
+<td class="right padl1 padr1">875</td>
+<td class="center">=</td>
+<td class="right padl1 padr1">437</td>
+</tr>
+
+</table>
+
+<p>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:</p>
+
+<table class="nowrap" summary="Table page 165-2">
+
+<tr>
+<td>&nbsp;</td>
+<td class="right padl1 padr1">1</td>
+<td class="center">lb.</td>
+<td class="center padl1 padr1">=</td>
+<td class="right">2968th</td>
+<td class="left padl1">part of a chaldron.</td>
+</tr>
+
+<tr>
+<td class="left">One peck</td>
+<td class="right padl1 padr1">20</td>
+<td>&nbsp;</td>
+<td class="center">=</td>
+<td class="right">148th</td>
+<td class="center">ditto.</td>
+</tr>
+
+<tr>
+<td class="left">One bushel</td>
+<td class="right padl1 padr1">82</td>
+<td>&nbsp;</td>
+<td class="center">=</td>
+<td class="right">36th</td>
+<td class="center">ditto.</td>
+</tr>
+
+<tr>
+<td class="left">One sack</td>
+<td class="right padl1 padr1">248</td>
+<td>&nbsp;</td>
+<td class="center">=</td>
+<td class="right">12th</td>
+<td class="center">ditto.</td>
+</tr>
+
+</table>
+
+<p><span class="smcap">Rule.</span>&mdash;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.</p>
+
+<p><span class="smcap">Example.</span>&mdash;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.</p>
+
+<hr class="sect" />
+
+<p><span class="pagenum"><a name="Page_166" id="Page_166">[166]</a></span></p>
+
+<h3>DESCRIPTION<br />
+<span class="fsize60">OF</span><br />
+THE GAS-LIGHT APPARATUS.</h3>
+
+<h4><a href="#Plate1">PLATE I.</a></h4>
+
+<p>Exhibits a perspective view of a gas-light apparatus,<a name="FNanchor_40" id="FNanchor_40"></a><a href="#Footnote_40" class="fnanchor">[40]</a>
+for lighting factories, or small districts of
+houses. It consists of the following parts: which
+may be considered separately.</p>
+
+<div class="footnote">
+
+<p><a name="Footnote_40" id="Footnote_40"></a><a href="#FNanchor_40"><span class="label">[40]</span></a> This apparatus was erected by Mr. <span class="smcap">Clegg</span>, and is now in
+action at Mr. <span class="smcap">Ackerman</span>&#8217;s establishment, in this metropolis.</p></div>
+
+<p><a href="#Plate1"><span class="smcap">Fig.</span> 1.</a> The <em class="italic">Retort Furnace</em>, for distilling the
+coals. It is built of brick-work. The bricks which
+are exposed to the immediate action of the fire,
+are <em class="italic">Welch tumps</em>, or fire-bricks; they are bedded
+in clay, or Windsor loam.</p>
+
+<p><a href="#Plate1"><span class="smcap">Fig.</span> 2.</a> The <em class="italic">Tar Cistern</em>, 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.</p>
+
+<p><span class="pagenum"><a name="Page_167" id="Page_167">[167]</a></span></p>
+
+<p><a href="#Plate1"><span class="smcap">Fig.</span> 3.</a> The <em class="italic">Lime Machine</em>, for purifying the
+crude coal-gas, and to render it fit for use. The
+construction of this machine will be explained in
+<a href="#Plate7">plate <span class="smcap">VII</span></a>. It is put together of cast-iron plates.</p>
+
+<p><a href="#Plate1"><span class="smcap">Fig.</span> 4.</a> The <em class="italic">Gasometer</em>, for collecting and preserving
+the purified gas, and for distributing and
+applying it as occasion may require. It consists
+of two principal parts&mdash;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.</p>
+
+<p>The action of these different parts of the apparatus
+will be obvious from the following explanation:</p>
+
+<p><span class="smcapall">A</span>, <span class="smcapall">A</span>, are two iron retorts, placed horizontally,
+and side by side, in the furnace; the mouth of the<span class="pagenum"><a name="Page_168" id="Page_168">[168]</a></span>
+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.</p>
+
+<p>When the operation commences, the inner vessel
+of the gasometer, <a href="#Plate1">fig. 4</a> 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 <span class="smcapall">B</span>, <span class="smcapall">B</span>, into the horizontal pipe or main
+condenser <span class="smcapall">C</span>, with which they are connected. The
+liquid which is distilled, collects in the pipe, or
+main condenser, <span class="smcapall">C</span>, where it is retained until its
+quantity has risen so high as to discharge itself into
+the pipe <span class="smcapall">D</span>, which is connected with the upper part
+of one of the extremities of the condenser, <span class="smcapall">C</span>. One
+of the extremities of the pipes, <span class="smcapall">B</span>, <span class="smcapall">B</span>, therefore become
+immersed into the liquid contained in the
+main condenser or pipe <span class="smcapall">C</span>, whilst the vaporous or
+condensible fluid, after having overcome the pressure
+there opposed to it, is transported into the pipe <span class="smcapall">E</span>,
+which, after passing in a serpentine direction, <span class="smcapall">E</span>, <span class="smcapall">E</span>,<span class="pagenum"><a name="Page_169" id="Page_169">[169]</a></span>
+&amp;c. through the exterior vessel or cistern of the gasometer,
+terminates in the tar-vessel, <a href="#Plate1">fig. 2</a>. Thus the
+vaporous fluids are condensed by passing through the
+serpentine pipe, <span class="smcapall">E</span>, <span class="smcapall">E</span>, &amp;c. and become deposited in
+the tar-cistern, <a href="#Plate1">fig. 2</a>; whilst the non-condensible or
+gazeous products are made to proceed by the pipe <span class="smcapall">F</span>,
+which branches off from the pipe <span class="smcapall">E</span>, into the lime
+machine, <a href="#Plate1">fig. 3</a>. 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 <span class="smcapall">G</span>,
+into the perpendicular pipe <span class="smcapall">H</span>, 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 <span class="smcapall">I</span>, 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 <span class="smcapall">H</span>, displaces the water from
+the receiver <span class="smcapall">I</span>, 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 <span class="smcapall">I</span>, 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<span class="pagenum"><a name="Page_170" id="Page_170">[170]</a></span>
+with this substance in the lime machine, <a href="#Plate1">fig. 3</a>.
+After rising through the water in the gasometer
+cistern, it enters into the gasometer, which then ascends
+as the gas accumulates in it.</p>
+
+<p>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 <span class="smcapall">K</span>, to the burners, or main
+pipe, which communicates with the gas burners or
+lamps. <span class="smcapall">L</span>, 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,
+<span class="smcapall">L</span>, may be conveyed by the curved pipe <span class="smcapall">M</span>, without
+admitting common air. <span class="smcapall">N</span>, <span class="smcapall">N</span>, 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<span class="pagenum"><a name="Page_171" id="Page_171">[171]</a></span>
+machine, the contents of which should be renewed
+occasionally. This pipe also conveys the necessary
+water into the barrel, <span class="smcapall">L</span>. <span class="smcapall">O</span>, is a waste-pipe, to convey
+the water as it becomes impregnated with the
+impurities of the gas, out of the gasometer cistern.
+<span class="smcapall">P</span>, is an agitator, to stir up the contents of the lime
+machine occasionally, <span class="smcapall">Q</span>, <span class="smcapall">Q</span>, are two iron rods, which
+serve as stays to guide the motion of the gasometer.
+<span class="smcapall">R</span>, 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. <span class="smcapall">S</span>, is the waste
+pipe of the lime machine, to remove the insoluble
+parts of the lime. <span class="smcapall">T</span>, 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. <span class="smcapall">U</span> 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.</p>
+
+<p>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<span class="pagenum"><a name="Page_172" id="Page_172">[172]</a></span>
+the right-hand corner of <a href="#Plate7">plate VII.</a> 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.</p>
+
+<h4><a href="#Plate2">PLATE II.</a></h4>
+
+<p>Represents a Portable experimental Gas Apparatus
+for exhibiting, in the small way, the general
+nature of the gas-light illumination.&mdash;It is described
+<a href="#Page_79">page 79</a>.</p>
+
+<h4><a href="#Plate3">PLATES III.</a> <a href="#Plate4">IV.</a> <a href="#Plate5">V.</a></h4>
+
+<p>Show designs of various kinds of Gas Lamps,
+Chandeliers, Candelabras, &amp;c.&mdash;See <a href="#Page_114">pages 114</a>, <a href="#Page_118">118</a>,
+<a href="#Page_140">140</a>.</p>
+
+<h4><a href="#Plate6">PLATE VI.</a></h4>
+
+<p><a href="#Plate6"><span class="smcap">Fig.</span> 1.</a> Exhibits a design of the <em class="italic">gasometer
+framing</em>, or <em class="italic">skeleton</em>, which serves to give stability
+and strength to the gasometer. It consists of
+wooden frame work, marked <span class="smcapall">A</span>, <span class="smcapall">A</span>, <span class="smcapall">A</span>, interlaced<span class="pagenum"><a name="Page_173" id="Page_173">[173]</a></span>
+with iron rods, <span class="smcapall">B</span>, <span class="smcapall">B</span>, <span class="smcapall">B</span>, &amp;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.</p>
+
+<p>The rest of the sketches represent various kinds
+of gas pipes employed as <em class="italic">mains</em> for conveying the
+gas, and the methods of connecting them.</p>
+
+<p><a href="#Plate6"><span class="smcap">Fig.</span> 2.</a> Represents a longitudinal section of a
+<em class="italic">Spigot</em> and <em class="italic">Faucet Pipe</em>. These kinds of pipes are
+applicable in most cases as mains for conveying gas.
+<span class="smcapall">A</span>, is called the spigot, and <span class="smcapall">B</span>, the faucet. They
+are joined together, and made air tight, by iron
+cement, the composition of which is as follows:</p>
+
+<p>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.</p>
+
+<p>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.</p>
+
+<p>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<span class="pagenum"><a name="Page_174" id="Page_174">[174]</a></span>
+proportion of iron,) all the parts of which cohere
+strongly together.</p>
+
+<p>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<sup>1</sup>&#8260;<sub>2</sub> inches deep, and has the spigot inserted
+1<sup>1</sup>&#8260;<sub>2</sub> 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<sup>1</sup>&#8260;<sub>2</sub>
+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.</p>
+
+<p><a href="#Plate6"><span class="smcap">Fig.</span> 3.</a> 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.</p>
+
+<p><a href="#Plate6"><span class="smcap">Fig.</span> 4.</a> Represents a longitudinal section of two
+flanch pipes, and the modes of connecting them.
+<span class="smcapall">A</span> and <span class="smcapall">B</span>, show the parts of the pipes; and <span class="smcapall">C</span> and
+<span class="smcapall">D</span>, the flanches. These pipes are also joined together,
+and rendered air-tight, by interposing between<span class="pagenum"><a name="Page_175" id="Page_175">[175]</a></span>
+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.</p>
+
+<p><a href="#Plate6"><span class="smcap">Fig.</span> 5.</a> Profile view of the same kind of pipes
+connected together, <span class="smcapall">A</span> and <span class="smcapall">B</span>, the pipes; <span class="smcapall">C</span> and <span class="smcapall">D</span>,
+the flanches; <span class="smcapall">E</span> and <span class="smcapall">F</span>, the bolts.</p>
+
+<p><a href="#Plate6"><span class="smcap">Fig.</span> 6.</a> 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.</p>
+
+<p><a href="#Plate6"><span class="smcap">Fig.</span> 7.</a> Exhibits the method of connecting spigot
+and faucet pipes when they have a round turn. <span class="smcapall">A</span>
+and <span class="smcapall">B</span>, the junctures of the pipes.</p>
+
+<p><a href="#Plate6"><span class="smcap">Fig.</span> 8.</a> Represents a longitudinal section of the
+mode of joining pipes by means of what is called
+a <em class="italic">thimble joint</em>. The junctures of the pipes to be
+connected, are made air tight, as mentioned already,
+by iron cement. <span class="smcapall">A</span>, the thimble or small cylinder,
+with projecting edges, which unites the pipes <span class="smcapall">B</span>, <span class="smcapall">C</span>.</p>
+
+<p><a href="#Plate6"><span class="smcap">Fig.</span> 9.</a> 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.</p>
+
+<p><a href="#Plate6"><span class="smcap">Fig.</span> 10.</a> Section of the same.</p>
+
+<p><a href="#Plate6"><span class="smcap">Fig.</span> 11.</a> Represents a profile view of what is
+called the <em class="italic">saddle joint</em>. It is employed for taking
+off a branch-pipe. The branch has a piece <span class="smcapall">A</span> <span class="smcapall">B</span>,
+formed on its end, and fits round one-half of the
+outside of the pipe from which it is to proceed.
+<span class="smcapall">C</span>, is called the saddle, which fits round the other
+half of the pipe. The parts are secured together<span class="pagenum"><a name="Page_176" id="Page_176">[176]</a></span>
+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.</p>
+
+<p><a href="#Plate6"><span class="smcap">Fig.</span> 12.</a> Section of the saddle-joint.</p>
+
+<p>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.</p>
+
+<p><a href="#Plate6"><span class="smcap">Fig.</span> 13.</a> Shows a reservoir for collecting the water
+of condensation which might accumulate in the
+pipes. It consists of a receptacle, <span class="smcapall">A</span>, in which the
+water may pass; <span class="smcapall">B</span>, 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.</p>
+
+<p><span class="pagenum"><a name="Page_177" id="Page_177">[177]</a></span></p>
+
+<h4><a href="#Plate7">PLATE VII.</a></h4>
+
+<p>Exhibits a perpendicular section of a gas-light
+apparatus, calculated for lighting towns, or large
+districts of streets and houses.</p>
+
+<p><a href="#Plate7"><span class="smcap">Fig.</span> 1.</a> 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. <span class="smcapall">A</span>, <span class="smcap">A,</span> shows two of the retorts
+placed horizontally above each other; <span class="smcapall">B</span>, the fire-place;
+<span class="smcapall">C</span>, the flue which causes the fire to circulate
+round the retorts so as to heat them equally in
+every part; <span class="smcapall">D</span>, the opening of the flue where the
+fire passes into the chimney; <span class="smcapall">E</span>, the ash-pit; <span class="smcapall">F</span>, a
+chamber in front of the retort furnace, into which
+the orifice or mouth of the retorts project; <span class="smcapall">G</span>, <span class="smcapall">G</span>, the
+doors of the chamber, to enable the workmen to
+charge and discharge the retorts; <span class="smcapall">H</span>, a funnel shaped
+hole at the floor of the chamber <span class="smcapall">F</span>, through which
+the red hot coke as it is discharged from the retorts
+passes into the arched vault <span class="smcapall">I</span>; <span class="smcapall">K</span>, the syphon tube;
+<span class="smcapall">L</span>, the horizontal condenser<a name="FNanchor_41" id="FNanchor_41"></a><a href="#Footnote_41" class="fnanchor">[41]</a>&mdash;the action of both of
+these pipes have been already explained, <a href="#Page_168">p. 168</a>;
+<span class="smcapall">M</span>, main pipe, which conveys the liquid substances
+from the condenser, to the tar cistern, <a href="#Plate7">fig. 3</a>, and<span class="pagenum"><a name="Page_178" id="Page_178">[178]</a></span>
+which conducts also the gazeous products into the
+lime machine, <a href="#Plate7">fig. 2</a>; <span class="smcapall">N</span> <span class="smcapall">N</span>, shows that part of the
+pipe which is interposed between the tar cistern,
+<a href="#Plate7">fig. 3</a>, and the condensing pipe <span class="smcapall">M</span>,&mdash;it passes in a
+serpentine direction along the inner sides of the
+gasometer cistern, and, like the so-called <em class="italic">worm</em> in
+a distillatory apparatus, condenses the products
+which escape in a vaporous state from the condenser
+<span class="smcapall">L</span>; <span class="smcapall">O</span>, shows the place where the serpentine pipe
+<span class="smcapall">N</span> <span class="smcapall">N</span>, passes again out of the gasometer cistern, and
+its communication with the lime machine, <a href="#Plate7">fig. 2</a>, and
+tar chamber, <a href="#Plate7">fig. 3</a>. The action of the lime machine
+is as follows: The liquid products evolved from the
+coal, having been deposited in the tar cistern, <a href="#Plate7">fig. 3</a>,
+by means of the serpentine pipe <span class="smcapall">N</span>, <span class="smcapall">N</span>, the gazeous products
+which accompany it, are conveyed by means of
+the pipe <span class="smcapall">P</span>, which branches out from the pipe <span class="smcapall">O</span>, into
+the interior receptacle of the lime machine marked <span class="smcapall">Q</span>,
+which consists of a vessel open at the bottom, and
+closed at the top, where it communicates with the
+pipe <span class="smcapall">O</span>. As the gas accumulates in the interior part <span class="smcapall">Q</span>,
+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 <span class="smcapall">R</span>, <span class="smcapall">R</span>, <span class="smcapall">R</span>, <span class="smcapall">R</span>, into the outer
+vessel, <span class="smcapall">S</span>, of the lime machine and from thence it is
+conducted away by the pipe <span class="smcapall">T</span>, <span class="smcapall">T</span>, <span class="smcapall">T</span>, into the additional
+washing apparatus, of the gasometer; <a href="#Plate7">fig. 4</a>,
+the construction of this apparatus, greatly resembles
+the lime machine, <a href="#Plate7">fig. 2</a>, namely, <span class="smcapall">V</span>, is a water
+pipe, proceeding from a cistern <span class="smcapall">U</span>, placed 3 or 4 feet
+above the orifice of the pipe <span class="smcapall">V</span>; <span class="smcapall">T</span>, <span class="smcapall">T</span>, is the gas-pipe,<span class="pagenum"><a name="Page_179" id="Page_179">[179]</a></span>
+covered with a hood, marked <span class="smcapall">W</span>, and immersed in a
+small cistern, having horizontal perforated shelves,
+like those in the lime machine&mdash;they fit close to the
+hood. The gas which enters the hood <span class="smcapall">W</span>, meets with
+a shower of water delivered by the pipe <span class="smcapall">V</span>. 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; <span class="smcapall">Y</span>, is a waste pipe,
+the lower extremity of which is sealed by being immersed
+in water,&mdash;it serves to carry away the water
+delivered by the pipe <span class="smcapall">V</span>, 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 <span class="smcapall">L</span>, by means of the
+pipe <span class="smcapall">K</span>, 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 <span class="smcapall">K</span>, <span class="smcapall">K</span>, becomes immersed and hermetically
+sealed by the liquid which the condenser <span class="smcapall">L</span>, 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 <span class="smcapall">M</span>, from whence they are
+transported into the tar cistern, <a href="#Plate7">fig. 3</a>, by means of
+the system of pipes <span class="smcapall">N</span>, <span class="smcapall">N</span>, <span class="smcapall">O</span>, whilst the gazeous products
+are made to pass by means of the branch
+pipe <span class="smcapall">P</span>, into the lime machine, <a href="#Plate7">fig. 2</a>. From this
+part of the apparatus the gas passes through the
+pipe <span class="smcapall">T</span>, <span class="smcapall">T</span>, <span class="smcapall">T</span>, into the additional or smaller washing
+apparatus placed upon a tressel in the cistern of the<span class="pagenum"><a name="Page_180" id="Page_180">[180]</a></span>
+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 <span class="smcapall">A</span>, closed at the
+top, and fixed in one corner of the gasometer, but
+open at the bottom; it includes another pipe marked
+<span class="smcapall">B</span>, which communicates with the main pipe leading
+to the burners, or place where the gas is wanted. The
+pipe <span class="smcapall">A</span>, which slides over the pipe <span class="smcapall">B</span>, is perforated at
+the top, the gas passes through these perforations
+and is thus made to enter into the pipe <span class="smcapall">B</span>, and
+disposed of as mentioned. <span class="smcapall">C</span>, <span class="smcapall">C</span>, 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 <span class="smcapall">D</span>, which reaches
+through the roof of the gasometer house, and thus
+the superfluous quantity of gas is conveyed away
+into the open air.</p>
+
+<div class="footnote">
+
+<p><a name="Footnote_41" id="Footnote_41"></a><a href="#FNanchor_41"><span class="label">[41]</span></a> 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, &amp;c. deposited in it, to seal
+the pipes <span class="smcapall">K</span>, <span class="smcapall">K</span>, and not to discharge itself into the pipe <span class="smcapall">M</span>, till
+this has been effected. The partition is seen in the drawing.</p></div>
+
+<p>The cylindrical vessel <span class="smcapall">P</span>, of <a href="#Plate7">fig. 3</a>, surrounding
+the orifice of the pipe <span class="smcapall">O</span>, which delivers the tar into
+the tar cistern, <a href="#Plate7">fig. 3</a>, 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
+<span class="smcapall">L</span>, is placed, as shown in the drawing, higher
+than the level of the water in the gasometer cistern,<span class="pagenum"><a name="Page_181" id="Page_181">[181]</a></span>
+to allow a free descent of the distillatory liquids as
+they pass from this vessel along into the pipes <span class="smcapall">M</span>, <span class="smcapall">N</span>, <span class="smcapall">O</span>,
+&amp;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&mdash;<span class="smcapall">E</span>, <span class="smcapall">E</span>, are two iron stays&mdash;<span class="smcapall">G</span>, <span class="smcapall">G</span>, are
+friction wheels.</p>
+
+<hr class="sect" />
+
+<h3 class="light"><i>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.</i><a name="FNanchor_42" id="FNanchor_42"></a><a href="#Footnote_42" class="fnanchor">[42]</a></h3>
+
+<div class="footnote">
+
+<p><a name="Footnote_42" id="Footnote_42"></a><a href="#FNanchor_42"><span class="label">[42]</span></a> For this elegant contrivance we are also indebted to
+Mr. <span class="smcap">Clegg</span>.</p></div>
+
+<p>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&mdash;see <a href="#Page_88">p. 88</a>, and <a href="#Page_167">167</a>. To
+render its pressure uniform, we first take the <em class="italic">absolute</em>
+weight of that part of the gasometer which becomes
+immersed in the water, and knowing the <em class="italic">specific
+weight</em> 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<span class="pagenum"><a name="Page_182" id="Page_182">[182]</a></span>
+of which the gasometer is composed. For example,
+let us suppose that the part of the gasometer which
+becomes immersed in water weighs 861 <i>lb.</i> 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<i>lb.</i> 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<i>lbs.</i> then the chain
+of the gasometer equal in length to the height of
+the gasometer, immersed into the water must weigh
+224<i>lb.</i> 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.</p>
+
+<hr class="sect" />
+
+<h3>DIRECTIONS TO WORKMEN<br />
+<span class="fsize60">ATTENDING</span><br />
+THE GAS-LIGHT APPARATUS<a name="FNanchor_43" id="FNanchor_43"></a><a href="#Footnote_43" class="fnanchor">[43]</a>.</h3>
+
+<div class="footnote">
+
+<p><a name="Footnote_43" id="Footnote_43"></a><a href="#FNanchor_43"><span class="label">[43]</span></a> Copied from a printed direction drawn up by Mr. Clegg,
+for the use of workmen.</p></div>
+
+<p>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:&mdash;Take<span class="pagenum"><a name="Page_183" id="Page_183">[183]</a></span>
+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,
+&amp;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.</p>
+
+<p>The bridge or row of bricks of the flue <span class="smcapall">C</span>, 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.</p>
+
+<p>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&#8217;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<span class="pagenum"><a name="Page_184" id="Page_184">[184]</a></span>
+it, it will take fire, and perhaps appear like a small
+blue flame&mdash;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,&mdash;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.</p>
+
+<p>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.</p>
+
+<p><span class="pagenum"><a name="Page_185" id="Page_185">[185]</a></span></p>
+
+<hr class="sect" />
+
+<h3>ESTIMATE<br />
+<span class="fsize60">OF</span><br />
+THE PRICE<br />
+<span class="fsize60">OF</span><br />
+A GAS-LIGHT APPARATUS,<br />
+<span class="fsize80"><em class="italic">IF ERECTED IN LONDON</em>,</span></h3>
+
+<p class="center">Capable of affording, every 24 hours, Light equal to 40,000 Tallow
+Candles, six in the pound, burning one hour.</p>
+
+<table summary="Table page 185">
+
+<tr>
+<th>&nbsp;</th>
+<th class="center padl3 padr1">&pound;.</th>
+<th class="center padl1 padr1">s.</th>
+</tr>
+
+<tr>
+<td class="left top padr3">Gasometer, to contain 10,000 cubic feet of gas</td>
+<td class="right bot padl1 padr1">236</td>
+<td class="right bot padl1 padr1">0</td>
+</tr>
+
+<tr>
+<td class="left top padr3">Wheel-work, regulating chain, ballance-weight for ditto, with wooden framing</td>
+<td class="right bot padl1 padr1">160</td>
+<td class="right bot padl1 padr1">11</td>
+</tr>
+
+<tr>
+<td class="left top padr3">Wrought iron cistern for gasometer&mdash;36 feet wide, 24 feet long and 16 feet deep</td>
+<td class="right bot padl1 padr1">500</td>
+<td class="right bot padl1 padr1">0</td>
+</tr>
+
+<tr>
+<td colspan="3" class="center">(<em class="italic">It would weigh about 16 tons.</em>)</td>
+</tr>
+
+<tr>
+<td class="left top padr3">Wooden framing built around it, to secure ditto</td>
+<td class="right bot padl1 padr1">150</td>
+<td class="right bot padl1 padr1">0</td>
+</tr>
+
+<tr>
+<td class="left top padr3">Condenser, cistern and communicating pipes</td>
+<td class="right bot padl1 padr1">126</td>
+<td class="right bot padl1 padr1">0</td>
+</tr>
+
+<tr>
+<td class="left top padr3">Lime machine, made of cast iron plates</td>
+<td class="right bot padl1 padr1">82</td>
+<td class="right bot padl1 padr1">0</td>
+</tr>
+
+<tr>
+<td class="left top padr3">Gasometer-house, built of frame-work and weather-boarded</td>
+<td class="right bot padl1 padr1">250</td>
+<td class="right bot padl1 padr1">0</td>
+</tr>
+
+<tr>
+<td class="left top padr3">Twenty-four retorts set in brick-work, with furnaces for ditto, compleat</td>
+<td class="right bot padl1 padr1">336</td>
+<td class="right bot padl1 padr1">0</td>
+</tr>
+
+<tr>
+<td class="left top padr3">Sundries</td>
+<td class="right bot padl1 padr1 bb">100</td>
+<td class="right bot padl1 padr1 bb">0</td>
+</tr>
+
+<tr>
+<td>&nbsp;</td>
+<td class="right bot padl1 padr1">&pound; 1940</td>
+<td class="right bot padl1 padr1">11</td>
+</tr>
+
+</table>
+
+<hr class="tb" />
+
+<p>A gas-light apparatus complete for work, capable of affording
+every twenty-four hours a quantity of light equal to
+1,400 Argand&#8217;s Lamps, each lamp equal in intensity to
+six candles, six in the pound, burning for five hours, will
+cost 3,500<i>l.</i> if erected in this metropolis.</p>
+
+<p><span class="pagenum"><a name="Page_186" id="Page_186">[186]</a></span></p>
+
+<h3 class="light">LONDON Price List of the most essential articles<a name="FNanchor_44" id="FNanchor_44"></a><a href="#Footnote_44" class="fnanchor">[44]</a> employed
+in the erection of a Gas-Light apparatus.</h3>
+
+<div class="footnote">
+
+<p><a name="Footnote_44" id="Footnote_44"></a><a href="#FNanchor_44"><span class="label">[44]</span></a> 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.</p></div>
+
+<table class="nowrap" summary="Table page 186-1">
+
+<tr>
+<th colspan="10" class="center">Sheet-iron pipes brazed.</th>
+</tr>
+
+<tr>
+<th colspan="3">&nbsp;</th>
+<th class="center padl1 padr1"><i>s.</i></th>
+<th colspan="2" class="center padl1 padr1"><i>d.</i></th>
+<th colspan="4">&nbsp;</th>
+</tr>
+
+<tr>
+<td>&nbsp;</td>
+<td class="left padl0 padr1 narrow"><sup>1</sup>&#8260;<sub>4</sub></td>
+<td class="left padr3">inch in diameter</td>
+<td class="right padl1 padr1">0</td>
+<td class="right padl1 padr0">4</td>
+<td>&nbsp;</td>
+<td class="center padl1 padr1">a foot</td>
+<td rowspan="14" class="bt br bb narrow">&nbsp;</td>
+<td rowspan="14" class="left padl0 narrow">-</td>
+<td rowspan="14" class="left wrappable">in 15<br />to 18<br />feet<br />lengths.</td>
+</tr>
+
+<tr>
+<td>&nbsp;</td>
+<td class="left padl0 padr1"><sup>3</sup>&#8260;<sub>8</sub></td>
+<td class="left padr3">ditto</td>
+<td class="right padl1 padr1">0</td>
+<td class="right padl1 padr0">4</td>
+<td>&nbsp;</td>
+<td class="center padl1 padr1">ditto</td>
+</tr>
+
+<tr>
+<td>&nbsp;</td>
+<td class="left padl0 padr1"><sup>1</sup>&#8260;<sub>2</sub></td>
+<td class="left padr3">ditto</td>
+<td class="right padl1 padr1">0</td>
+<td class="right padl1 padr0">5</td>
+<td>&nbsp;</td>
+<td class="center padl1 padr1">ditto</td>
+</tr>
+
+<tr>
+<td>&nbsp;</td>
+<td class="left padl0 padr1"><sup>5</sup>&#8260;<sub>8</sub></td>
+<td class="left padr3">ditto</td>
+<td class="right padl1 padr1">0</td>
+<td class="right padl1 padr0">6</td>
+<td>&nbsp;</td>
+<td class="center padl1 padr1">ditto</td>
+</tr>
+
+<tr>
+<td>&nbsp;</td>
+<td class="left padl0 padr1"><sup>3</sup>&#8260;<sub>4</sub></td>
+<td class="left padr3">ditto</td>
+<td class="right padl1 padr1">0</td>
+<td class="right padl1 padr0">6</td>
+<td class="left padl0 padr1"><sup>1</sup>&#8260;<sub>2</sub></td>
+<td class="center padl1 padr1">ditto</td>
+</tr>
+
+<tr>
+<td>&nbsp;</td>
+<td class="left padl0 padr1"><sup>7</sup>&#8260;<sub>8</sub></td>
+<td class="left padr3">ditto</td>
+<td>&nbsp;</td>
+<td class="right padl1 padr0">7</td>
+<td>&nbsp;</td>
+<td class="center padl1 padr1">ditto</td>
+</tr>
+
+<tr>
+<td class="right padr0">1</td>
+<td>&nbsp;</td>
+<td class="left padr3">inch, ditto</td>
+<td class="right padl1 padr1">0</td>
+<td class="right padl1 padr0">7</td>
+<td class="left padl0 padr1"><sup>1</sup>&#8260;<sub>2</sub></td>
+<td class="center padl1 padr1">ditto</td>
+</tr>
+
+<tr>
+<td class="right padr0">1</td>
+<td class="left padl0 padr1"><sup>1</sup>&#8260;<sub>4</sub></td>
+<td class="left padr3">ditto</td>
+<td class="right padl1 padr1">0</td>
+<td class="right padl1 padr0">9</td>
+<td>&nbsp;</td>
+<td class="center padl1 padr1">ditto</td>
+</tr>
+
+<tr>
+<td class="right padr0">1</td>
+<td class="left padl0 padr1"><sup>1</sup>&#8260;<sub>2</sub></td>
+<td class="left padr3">ditto</td>
+<td class="right padl1 padr1">0</td>
+<td class="right padl1 padr0">10</td>
+<td class="left padl0 padr1"><sup>1</sup>&#8260;<sub>2</sub></td>
+<td class="center padl1 padr1">ditto</td>
+</tr>
+
+<tr>
+<td class="right padr0">1</td>
+<td class="left padl0 padr1"><sup>3</sup>&#8260;<sub>4</sub></td>
+<td class="left padr3">ditto</td>
+<td class="right padl1 padr1">0</td>
+<td class="right padl1 padr0">11</td>
+<td>&nbsp;</td>
+<td class="center padl1 padr1">ditto</td>
+</tr>
+
+<tr>
+<td class="right padr0">2</td>
+<td>&nbsp;</td>
+<td class="left padr3">inch, ditto</td>
+<td class="right padl1 padr1">1</td>
+<td class="right padl1 padr0">1</td>
+<td class="left padl0 padr1"><sup>1</sup>&#8260;<sub>2</sub></td>
+<td class="center padl1 padr1">ditto</td>
+</tr>
+
+<tr>
+<td class="right padr0">2</td>
+<td class="left padl0 padr1"><sup>1</sup>&#8260;<sub>4</sub></td>
+<td class="left padr3">ditto</td>
+<td class="right padl1 padr1">1</td>
+<td class="right padl1 padr0">4</td>
+<td>&nbsp;</td>
+<td class="center padl1 padr1">ditto</td>
+</tr>
+
+<tr>
+<td class="right padr0">2</td>
+<td class="left padl0 padr1"><sup>1</sup>&#8260;<sub>2</sub></td>
+<td class="left padr3">ditto</td>
+<td class="right padl1 padr1">1</td>
+<td class="right padl1 padr0">5</td>
+<td>&nbsp;</td>
+<td class="center padl1 padr1">ditto</td>
+</tr>
+
+<tr>
+<td class="right padr0">3</td>
+<td>&nbsp;</td>
+<td class="left padr3">inch, ditto</td>
+<td class="right padl1 padr1">1</td>
+<td class="right padl1 padr0">6</td>
+<td class="left padl0 padr1"><sup>1</sup>&#8260;<sub>2</sub></td>
+<td class="center padl1 padr1">ditto</td>
+</tr>
+
+<tr>
+<td colspan="3" class="left padr3">Copper pipes brazed <sup>1</sup>&#8260;<sub>4</sub> inch</td>
+<td class="right padl1 padr1">0</td>
+<td class="right padl1 padr0">4</td>
+<td>&nbsp;</td>
+<td class="center padl1 padr1">per foot</td>
+<td colspan="3">&nbsp;</td>
+</tr>
+
+<tr>
+<td colspan="3" class="left padr3">Ditto, ditto, ditto <sup>3</sup>&#8260;<sub>8</sub> inch</td>
+<td class="right padl1 padr1">0</td>
+<td class="right padl1 padr0">5</td>
+<td class="left padl0 padr1"><sup>1</sup>&#8260;<sub>2</sub></td>
+<td class="center padl1 padr1">ditto</td>
+<td colspan="3">&nbsp;</td>
+</tr>
+
+<tr>
+<td colspan="10" class="left">Gas-light cockspur burners with stop-cock 2s 6d to 3s 6d</td>
+</tr>
+
+<tr>
+<td colspan="10" class="left">Argand&#8217;s lamps, with glass-holders, from 3s to 4s 6d</td>
+</tr>
+
+</table>
+
+<table class="nowrap notop" summary="Table page 186-2">
+
+<tr>
+<td class="left padr3">Cast-iron retorts, weighing 7 cwt. at 15s 6d per cwt</td>
+<td class="right padr1 padl1">&pound;5</td>
+<td class="right padl1 padr1">8</td>
+<td class="right padl1 padr1">6</td>
+</tr>
+
+<tr>
+<td class="left padr3">Mouth-piece for ditto, compleat</td>
+<td class="right padl1 padr1">1</td>
+<td class="right padl1 padr1">14</td>
+<td class="right padl1 padr1">8</td>
+</tr>
+
+<tr>
+<td class="left padr3">Cast-iron door frames for retort furnace</td>
+<td class="right padl1 padr1">1</td>
+<td class="right padl1 padr1">0</td>
+<td class="right padl1 padr1">0</td>
+</tr>
+
+<tr>
+<td colspan="4" class="left">Furnace bars 10s. per cwt.</td>
+</tr>
+
+<tr>
+<td colspan="4" class="left">Sheet iron for gazometer (No. 23) 24s. per cwt.</td>
+</tr>
+
+<tr>
+<td colspan="4" class="left">Gazometer chains, 5d per lb.</td>
+</tr>
+
+<tr>
+<td colspan="4" class="left">Ballance weights [Plates] for gazometer, 9l 10s per ton.</td>
+</tr>
+
+<tr>
+<td colspan="4" class="left">Cast-iron cistern plates</td>
+</tr>
+
+<tr>
+<td colspan="4" class="left">----------------------- smaller size for lime machine, 18l per ton.</td>
+</tr>
+
+<tr>
+<td colspan="4" class="left">----------------------- middling size for tar cistern, 16l ditto</td>
+</tr>
+
+<tr>
+<td colspan="4" class="left">----------------------- largest size for gazometer cistern 14l ditto</td>
+</tr>
+
+</table>
+
+<table class="nowrap notop" summary="Table page 186-3">
+
+<tr>
+<td class="left">Cast-iron flanch pipes</td>
+<td class="right padl1 padr0">2</td>
+<td class="center narrow padl0 padr0">-</td>
+<td colspan="2" class="left padl0 padr1">inch diameter, at</td>
+<td class="right padr1">5s</td>
+<td>&nbsp;</td>
+<td class="left padl1 padr1">per yd. in</td>
+<td class="right padr1">6</td>
+<td class="left">feet lengths</td>
+</tr>
+
+<tr>
+<td class="center">ditto</td>
+<td class="right padl1 padr0">3</td>
+<td colspan="3" class="center">ditto</td>
+<td class="right padr1">6s</td>
+<td>&nbsp;</td>
+<td class="center">ditto</td>
+<td class="right padr1">6</td>
+<td class="center">ditto</td>
+</tr>
+
+<tr>
+<td class="center">ditto</td>
+<td class="right padl1 padr0">4</td>
+<td colspan="3" class="center">ditto</td>
+<td class="right padr1">8s</td>
+<td class="right padr1">6d</td>
+<td class="center">ditto</td>
+<td class="right padr1">9</td>
+<td class="center">ditto</td>
+</tr>
+
+<tr>
+<td class="center">ditto</td>
+<td class="right padl1 padr0">5</td>
+<td colspan="3" class="center">ditto</td>
+<td class="right padr1">10s</td>
+<td>&nbsp;</td>
+<td class="center">ditto</td>
+<td class="right padr1">9</td>
+<td class="center">ditto</td>
+</tr>
+
+<tr>
+<td class="center">ditto</td>
+<td class="right padl1 padr0">6</td>
+<td colspan="3" class="center">ditto</td>
+<td class="right padr1">12s</td>
+<td>&nbsp;</td>
+<td class="center">ditto</td>
+<td class="right padr1">9</td>
+<td class="center">ditto</td>
+</tr>
+
+<tr>
+<td class="center">ditto</td>
+<td class="right padl1 padr0">7</td>
+<td colspan="3" class="center">ditto</td>
+<td class="right padr1">13s</td>
+<td class="right padr1">6d</td>
+<td class="center">ditto</td>
+<td class="right padr1">9</td>
+<td class="center">ditto</td>
+</tr>
+
+<tr>
+<td class="center">ditto</td>
+<td class="right padl1 padr0">8</td>
+<td rowspan="4" class="bt br bb narrow">&nbsp;</td>
+<td rowspan="4" class="left padl0 narrow">-</td>
+<td rowspan="4" colspan="4" class="left">11l. 5s. per ton</td>
+<td rowspan="4" class="right padr1">9</td>
+<td rowspan="4" class="center">ditto</td>
+</tr>
+
+<tr>
+<td class="center">ditto</td>
+<td class="right padl1 padr0">9</td>
+</tr>
+
+<tr>
+<td class="center">ditto</td>
+<td class="right padl1 padr0">10</td>
+</tr>
+
+<tr>
+<td class="center">ditto</td>
+<td class="right padl1 padr0">11</td>
+</tr>
+
+</table>
+
+<table class="nowrap notop" summary="Table page 186-4">
+
+<tr>
+<td class="left"><sup>1</sup>&#8260;<sub>2</sub> inch nuts, screws and washers to put iron pipes together</td>
+<td class="right padl1 padr1">7d.</td>
+<td class="center">per lb</td>
+</tr>
+
+<tr>
+<td class="left"><sup>5</sup>&#8260;<sub>8</sub> ditto</td>
+<td class="right padl1 padr1">7d.</td>
+<td class="center">ditto</td>
+</tr>
+
+<tr>
+<td class="left"><sup>3</sup>&#8260;<sub>4</sub> ditto</td>
+<td class="right padl1 padr1">6d.</td>
+<td class="center">ditto</td>
+</tr>
+
+<tr>
+<td class="left">English bar-iron</td>
+<td class="right padl1 padr1">13l.</td>
+<td class="center">per ton</td>
+</tr>
+
+<tr>
+<td class="left">Best, ditto</td>
+<td class="right padl1 padr1">18l.</td>
+<td class="center">ditto</td>
+</tr>
+
+</table>
+
+<p class="center fsize150"><em class="italic">FINIS.</em></p>
+
+<div class="figcenter"><a name="Plate6" id="Plate6"></a>
+<img src="images/illo208.jpg" alt="Gasometer frame and pipe connectors" width="364" height="600" />
+<p class="largeimg"><a href="images/lg208.jpg">Larger image</a> (345 kB)</p>
+</div>
+
+<div class="figcenter"><a name="Plate7" id="Plate7"></a>
+<img src="images/illo210.jpg" alt="Gas works" width="600" height="499" />
+<p class="largeimg"><a href="images/lg210.jpg">Larger image</a> (302 kB)</p>
+</div>
+
+<div class="tnbottom"><a name="TN" id="TN"></a>
+
+<h2>Transcriber&#8217;s notes</h2>
+
+<p>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.<br />
+The errata have already been incorporated in the text; the error mentioned as occurring on page 24 actually occurs on page 22.<br />
+The original language, including inconsistencies in spelling, hyphenation, punctuation, formatting, etc. has been retained, except as mentioned below.<br />
+The e-reader cover image has been created for this project, and is placed in the public domain.<br />
+Unclear parts of the text have been checked against the on-line copy of this book of the Eidgen�ssische Technische Hochschule Z�rich.<br />
+Fractions like <sup>1</sup>&#8260;<sub>2</sub> and 1-10th have both been retained.<br />
+Page 90, Van Dieman, Troostwyck: Jan Rudolph Deiman and Adriaan Paets van Troostwijk.</p>
+
+<p>Changes made to the text:<br />
+Obvious punctuation and typographical errors have been corrected silently.<br />
+Some footnotes, tables and illustrations have been moved; some tables have been re-arranged.</p>
+
+<p>Other changes:<br />
+Page 23: any surfaces changed to any surface<br />
+Page 26: opening or shuting changed to opening or shutting<br />
+Page 47: A New changed to A new<br />
+Page 48: trafic changed to traffic; footnote [10]: corporated changed to incorporated (cf. errata)<br />
+Page 53: This combustion changed to The combustion (cf. errata)<br />
+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)<br />
+Page 67: 1250 + 2 = 2500 changed to 1250 &times; 2 = 2500<br />
+Page 69: Mr. <span class="smcap">Lee</span> changed to &#8220;Mr. <span class="smcap">Lee</span> for consistency<br />
+Page 72: closing quote mark added to letter<br />
+Page 96: pure coal- changed to pure coal-gas<br />
+Page 102: sub acetate changed to sub-acetate<br />
+Page 118: ball 6 changed to ball <i>b</i><br />
+Page 119: <i>e</i>, are changed to <i>e</i> <i>e</i>, are<br />
+Page 125: 180 degree changed to 180 degrees (cf. errata); footnote [28]: may he compleatly changed to may be compleatly<br />
+Page 131: and make changed to and makes<br />
+Page 132: coal changed to coal-tar (cf. errata)<br />
+Page 158: Nortou Falgate changed to Norton Falgate; a about changed to about<br />
+Page 165, table: 10,509 changed to 10,500.</p>
+
+</div><!--tnbottom-->
+
+
+
+
+
+
+
+
+<pre>
+
+
+
+
+
+End of the Project Gutenberg EBook of A Practical Treatise on Gas-light, by 
+Fredrick Accum
+
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+</pre>
+
+</body>
+</html>
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@@ -0,0 +1,4961 @@
+Project Gutenberg's A Practical Treatise on Gas-light, by Fredrick Accum
+
+This eBook is for the use of anyone anywhere at no cost and with
+almost no restrictions whatsoever.  You may copy it, give it away or
+re-use it under the terms of the Project Gutenberg License included
+with this eBook or online at www.gutenberg.org
+
+
+Title: 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.
+
+Author: Fredrick Accum
+
+Release Date: January 2, 2014 [EBook #44567]
+
+Language: English
+
+Character set encoding: ASCII
+
+*** START OF THIS PROJECT GUTENBERG EBOOK A PRACTICAL TREATISE ON GAS-LIGHT ***
+
+
+
+
+Produced by Chris Curnow, Harry Lame and the Online
+Distributed Proofreading Team at http://www.pgdp.net (This
+file was produced from images generously made available
+by The Internet Archive)
+
+
+
+
+
+
+
+Transcriber's notes
+
+Italics in the original work are transcribed between _underscores_;
+small-capitals have been transcribed as all capitals. [::] represents
+the proportion symbol.
+
+More transcriber's notes and a list of corrections made may be found at
+the end of this text.
+
+
+[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 COLOURED 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 coloured
+_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 faggots 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
+
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