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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: 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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