GAS-LIGHT.
PRELIMINARY OBSERVATION.
A new art of procuring artificial light, which consists in burning the
gazeous fluid obtained by distillation from common pit-coal, has of late
engaged the attention of the public, under the name of _gas-light_.
The encouragement that has been given for some years past by the
legislature to this system of lighting, has induced certain individuals
to apply the coal-gas light for the illumination of streets, houses,
roads, and public edifices. And it is sufficiently known that a company
has been incorporated by charter under the name of the “_Gas Light and
Coke Company_,” to apply this new art of procuring light, by way of
experiment, on a large scale, in lighting the streets of the
metropolis.[10]
[10] An Act for granting certain powers and authorities to a company
to be incorporated by charter, called the “Gas Light and Coke
Company,” for making inflammable air for the lighting of the streets
of the metropolis, &c.--Session 1810, 50th Geo. III.
The power and authorities granted to this corporate body are very
restricted and moderate. The individuals composing it have no exclusive
privilege; their charter does not prevent other persons from entering
into competition with them. Their operations are confined to the
metropolis where they are bound to furnish not only a stronger and
better light to such streets and parishes as chuse to be lighted with
gas, but also at a cheaper price than shall be paid for lighting the
said streets with oil in the usual manner. The corporation is not
permitted to traffic in machinery for manufacturing or conveying the gas
into private houses, their capital or joint stock is limited to
200,000_l._ and His Majesty has the power of declaring the gas-light
charter void, if the company fail to fulfil the terms of it.
THEORY OF THE COMBUSTION OF COAL IN ELUCIDATION OF THE NATURE AND
PRODUCTION OF GAS LIGHT.
Pit-coal exists in this island in strata, which, as far as concerns many
hundred generations after us, may be pronounced inexhaustible; and is so
admirably adapted, both for domestic purposes and the uses of the arts,
that it is justly regarded as a most essential constituent of our
national wealth. Like all other bituminous substances, it is composed of
a fixed carbonaceous base or bitumen, united to more or less earthy and
saline matter constituting the ashes left behind when this substance is
burnt. The proportions of these parts differ considerably, in different
kinds of coal; and according to the prevalency of one or other of them,
so the coal is more or less combustible, and possesses the characters
of perfect pit-coal; and by various shades, passes from the most
inflammable canel-coal, into blind, Kilkenny, or stone-coal; and,
lastly, into a variety of earthy or stony substances; which, although
they are inflammable, do not merit the appellation of coal.
Every body knows that when pit-coals are burning in our grates, a flame
more or less luminous issues from them, and that they frequently emit
beautiful streams of flame remarkably bright. But besides the flame,
which is a peculiar gas in the state of combustion, heat expels from
coal an aqueous vapour, loaded with several kinds of ammoniacal salts, a
thick viscid fluid resembling tar, and some gases that are not of a
combustible nature. The consequence of which is, that the flame of a
coal-fire is continually wavering and changing, both in shape, as well
as brilliance and in colour, so that what one moment gave a beautiful
bright light, in the next, perhaps, is obscured by a stream of thick
smoke.
But if coals, instead of being suffered to burn in this way, are
submitted to distillation in close vessels, all its immediate
constituent parts may be collected. The bituminous part is melted out
in the form of tar. There is disengaged at the same time, a large
quantity of an aqueous fluid, contaminated with a portion of oil, and
various ammoniacal salts. A large quantity of carburetted hidrogen, and
other uninflammable gases, make their appearance, and the fixed base of
the coal remains behind in the distillatory apparatus in the form of a
carbonaceous substance, called coke.
All these products may be separately collected in different vessels. The
carburetted hidrogen, or coal-gas, may be freed from the non-inflammable
gases, and afterwards forced in streams out of small appertures, which,
when lighted, may serve as the flame of a candle to illuminate a room or
any other place. It is thus, that from pit-coal a native production of
this country, we may procure a pure, lasting, and copious light; which,
in other cases, must be derived from expensive materials, in part
imported from abroad.
It is chiefly upon the power of collecting the products afforded by
coal, with convenience and cheapness, that the promoters of the
gas-light illumination found their claims to public encouragement. They
conceive that the flame which pit-coal yields, as it is now consumed,
is turned to very little advantage: it is not only confined to one
place, where a red heat is more wanted than a brilliant flame, but it is
obscured, and sometimes entirely smothered, by the quantity of
incombustible materials that ascend along with it and pollute the
atmosphere.
That much inflammable matter is thus lost, is evident from facts that
come under our daily observation. We often see a flame suddenly burst
from the densest smoke, and as suddenly disappear; and if a light be
applied to the little jets that issue from the bituminous parts of the
coal, they will catch fire, and burn with a bright flame. A considerable
quantity of a gazeous fluid, capable of affording light and heat
continually escapes up the chimney, whilst another part is occasionally
ignited, and exhibits the phenomena of the flame and light of the fire.
The theory of the production of gas-light is therefore analogous to the
action of a lamp or candle. The wick of a candle being surrounded by the
flame, is in the same situation of the pit-coal exposed to distillation.
The office of the wick is chiefly to convey tallow, by capillary
attraction, to the place of combustion. As it is decomposed into
carburetted hidrogen gas it is consumed and flies off, another portion
succeeds; and in this way a continued current of tallow and maintenance
of flame are effected. See page 15.
The combustion of oil by means of a lamp depends on similar
circumstances. The tubes formed by the wick serve the same office as a
retort placed in a heated furnace through which the inflammable liquid
is transmitted. The oil is drawn up into these ignited tubes, and is
decomposed into carburetted hidrogen gas, and from the combustion of
this gas the illumination proceeds. See p. 15. What then does the
gas-light system attempt? Nothing more than to generate, by means of
sufficient furnaces and a reservoir of sufficient capacity, desired
quantities of the gas, which is the same material of the flame of
candles or lamps; and then by passing it through pipes to any desired
distance, to exhibit it there at the mouths of the conducting tubes, so
that it may be ignited for any desired purpose. The only difference
between this process and that of an ordinary candle or lamp, consists in
having the furnace at the manufactory, instead of its being in the wick
of the candle or lamp--in having the inflammable material distilled at
the station, instead of its present exhibitions in oil, wax, or tallow,
and then in transmitting the gas to any required distance, and igniting
it at the orifice of the conducting pipe instead of igniting it at the
apex of the wick. The principle is rational, and justified by the
universal mode in which all light is produced. Indeed, this discovery
ranks among the numerous recent applications of chemical science to the
purposes of life, which promise to be of the most general utility.
It is evident from the outline here given of the production and
application of coal-gas, that all the uses of pit-coal are not
exhausted; it will be sufficient to observe, that the complete analysis
of coal, which has been hitherto confined to the laboratory of the
chemist, requiring skill and nicety in the operator, and attended with
great trouble and expence, is now so far simplified, that many chaldrons
of coals may be decomposed by one gas-light apparatus in the space of
six hours, and all the component parts produced in their most useful
shape, at an expence out of all proportion below the value of the
products.
SKETCH OF THE RISE AND PROGRESS OF THE DISCOVERY AND APPLICATION OF
COAL-GAS, AS A SUBSTITUTE FOR PROCURING ARTIFICIAL LIGHT.
To assist the reader in comprehending the nature and object of
substituting coal-gas for tallow or oil, for the purpose of obtaining
light, it may be proper to touch slightly upon the successive
discoveries that have been made as to the decomposition of coal, and the
application of its different ingredients. Such a sketch will add to the
many examples that occur in the history of science and art, showing the
slow progress of mankind in following up known principles, or extracting
from acknowledged facts every possible advantage.
In the Philosophical Transactions of the Royal Society, V. XLI. so long
ago as the year 1739, is recorded a paper, exhibiting an account of some
experiments made by Dr. James Clayton, from which it appears that the
inflammable nature of coal-gas was then already known. Dr. Clayton
having distilled Newcastle coal, obtained, as products of the process,
an aqueous fluid, a black oil, and an inflammable gas, which he caught
in bladders, and by pricking these he was enabled to inflame the gas at
pleasure.
It is further known, that in the beginning of the last century, Dr.
Hales[11] on submitting pit-coal to a chemical examination, found, that
during the ignition of this fossil in close vessels, nearly one-third of
the coal became volatilized in the form of an inflammable vapour. Hence
the discovery of the inflammable nature of coal-gas can no longer be
claimed by any person now living.
[11] Vegetab. Statics, vol. I.
In the year 1767, the Bishop of Llandaff[12] examined the nature of the
vapour and gazeous products evolved during the distillation of pit-coal.
This learned philosopher noticed, that the volatile product is not only
inflammable as it issues from the distillatory vessel, but that it also
retained its inflammability after having been made to pass through
water, and suffered to ascend through two high curved tubes. The solid
matters obtained by this venerable prelate, were, an aqueous ammoniacal
fluid, a tenaceous oil, resembling tar, an ammoniacal liquor, and a
spongy coal, or coke.
[12] Watson’s Chemical Essays, vol. II.
The first discovery and application of the use of coal-gas for the
purpose of illumination is claimed by Mr. Murdoch.
Dr. W. Henry of Manchester, has published the following account[13] of
this discovery.
[13] Thompson’s System of Chemistry, vol. I. p. 52.
“In the year 1792, at which time Mr. Murdoch resided at Redruth, in
Cornwall, he commenced a series of experiments upon the quantity and
quality of the gases contained in different substances. In the course of
these he remarked, that the gas obtained by distillation from coal,
peat, wood, and other inflammable substances, burnt with great
brilliancy upon being set fire to; and it occurred to him, that by
confining and conducting it through tubes, it might be employed as an
economical substitute for lamps and candles. The distillation was
performed in iron retorts, and the gas conducted through tinned iron and
copper tubes to the distance of 70 feet. At this termination, as well as
at intermediate points, the gas was set fire to, as it passed through
apertures of different diameters and forms, purposely varied with a view
of ascertaining which would answer best. In some the gas issued through
a number of small holes like the head of a watering pan; in others it
was thrown out in thin long sheets; and again in others in circular
ones, upon the principle of Argand’s lamp. Bags of leather and of
varnished silk, bladders, and vessels of tinned iron, were filled with
the gas, which was set fire to, and carried about from room to room,
with a view of ascertaining how far it could be made to answer the
purpose of a moveable or transferable light. Trials were likewise made
of the different quantities and qualities of gas produced by coals of
various descriptions, such as the Swansea, Haverfordwest, Newcastle,
Shropshire, Staffordshire, and some kinds of Scotch coals.
“Mr. Murdoch’s constant occupations prevented his giving farther
attention to the subject at that time; but he again availed himself of a
moment of leisure to repeat his experiments upon coal and peat at Old
Cumnock, in Ayrshire, in 1797; and it may be proper to notice that both
these, and the former ones, were exhibited to numerous spectators, who,
if necessary, can attest them. In 1798, he constructed an apparatus at
Soho Foundry, which was applied during many successive nights to the
lighting of the building; when the experiments upon different apertures
were repeated and extended upon a large scale. Various methods were also
practised of washing and purifying the air, to get rid of the smoke and
smell. These experiments were continued, with occasional interruptions,
until the epoch of the peace in the spring of 1802, when the
illumination of the Soho manufactory afforded an opportunity of making a
public display of the new lights; and they were made to constitute a
principal feature in that exhibition.”
In the year 1803 and 1804, Mr. Winsor exhibited at the Lyceum in London
the general nature of this new mode of illumination though the
machinery for procuring, and the manner of purifying the gas, he kept a
secret. He exhibited the mode of conducting the gas through the house,
and a number of devices for chandeliers, lamps, and burners, by which it
might be applied. Among these he proposed long flexible tubes suspended
from the ceiling, or wall of the room, and at the end communicating with
burners or lamps of different kinds. This gentleman showed also by
experiment, that the flame of the gas-light, produced no smoke; that it
was not so dangerous as the flame of candles or lamps; that it could not
produce sparks; and that it was not so readily extinguished by gusts of
wind or torrents of rain.
Mr. WINSOR’s display of gas-lights took place more than two years before
Mr. MURDOCH’s priority of right was heard of.
In stating these facts I do not mean to say that Mr. MURDOCH derived the
hint of applying the coal-gas from the previous exhibition of Mr.
WINSOR, because it is quite within the bounds of probability that the
ideas of Mr. MURDOCH may have arisen totally independent of all
acquaintance with Mr. WINSOR’s.
The claims of invention, or the determination of the right of priority,
concerns the public only so far as the honour and estimation of any
useful discovery conferred on the inventor may induce other individuals
to devote their talents to similar pursuits; by means of which, more
discoveries may be made, and the subject of human invention become
extended, or rendered more useful. For as the mere benefits which
mankind may derive from any particular discovery, they are certainly
more indebted to the person who first applied the discovery to actual
practice, than to him who first made it, and merely illustrated it by
barren experiments. Mr. WINSOR certainly pressed on the mind of the
public with unremitted perseverance and diligence the extensive
application of gas-light in the year 1802, but he made no new discovery
with regard to the composition of coal; he did not even invent the mode
of conducting the gas through tubes; and if he has pointed out the
particulars of the process, he has made a very important, though not the
most brilliant improvement in this line of business. Mr. WINSOR’s
publications are, perhaps, but ill adapted to promote his cause; and the
exaggerated calculation which the sanguine mind of a discoverer is
naturally disposed to indulge in, have, to superficial observers, thrown
an air of ridicule and improbability on the whole scheme of lighting
with gas.
It may, however, be safely affirmed, that if the same facts had come
forward, under the sanction of some great name in the chemical or
philosophical world, the public incredulity would long since have been
subdued; and the plan, which for many years has been struggling for
existence, would have been eagerly adopted as a national object.
On the 18th of May, 1804, Mr. FREDERICK ALBERT WINSOR, took out a patent
for combining the saving and purifying of the inflammable gas (for
producing light and heat), the ammonia, tar, and other products of
pit-coal, with the manufacture of a superior kind of coke (see
Repertory, 2d Series, v. 172). And, lately, the same gentleman has taken
out a second patent, for further improvements in these processes.
In the year 1805, Mr. NORTHERN, of Leeds, also directed the attention
of the public to the application of coal-gas, as a substitute for tallow
light, as will be seen by the following extract of the Monthly Magazine
for April, 1805.
“I distilled in a retort, 50 ounces of pit-coal in a red heat, which
gave 6 ounces of a liquid matter covered with oil, more or less fluid as
the heat was increased or diminished. About 26 ounces of cinder remained
in the retort; the rest came over in the form of air, as it was
collected in the pneumatic apparatus. I mixed part of it with
atmospherical air, and fired it with the electric spark with a tolerable
explosion, which proves it to be hydrogene.--Whether any of the other
gases were mixed with it, I did not then determine. In the receiver I
found a fluid of an acid taste, with a great quantity of oil, and, at
the bottom, a substance resembling tar.
“The apparatus I make use of for producing light is a refiner’s
crucible, the top of which (after filling with coal) I close with a
metal cover, luted with clay or other luting, so as to prevent the
escape of the gas; a metal pipe is soldered into the cover, bent so as
to come under the shelf in the pneumatic trough, over which I place a
jar with a stop-cock and a small tube; the jar being previously filled
with water, the crucible I place on the common or other fire as is most
convenient; and as the heat increases in it, the gas is forced rapidly
through the water into the jar, and regularly displaces it. I then open
the cock and put fire to the gas, which makes its escape through the
small tube, and immediately a most beautiful flame ensues, perfectly
free from smoke or smell of any kind. A larger light, but not so vivid
or clear, will be produced without passing the gas through water, but
attended with a smoke somewhat greater than that of a lamp charged with
common oil.
“I have great hopes that some active mechanic or chemist will, in the
end, hit on a plan to produce light for large factories, and other
purposes, at a much less expence, by the above or similar means, than is
at present produced from oil.”
Soon afterwards, Mr. SAMUEL CLEGG[14] of Manchester, Engineer,
communicated an account of his method of lighting up manufactories with
gas-light to the Society of Arts, for which he received the silver
medal.
[14] This gentleman is at present engineer to the Gas-Light Company.
Since that time, the application of gas-light has spread rapidly, and
numerous manufactories and other establishments have been lighted by
coal-gas.
In France, the application of gas-lights to economical purposes, was
pointed out long before it was publicly introduced into this country. M.
LE BON had a house fitted up in Paris, in the winter of 1802, so as to
be entirely illuminated by gas-lights, which was seen by thousands with
admiration; and had a _brevet d’invention_ (patent) granted to him by
the French government, for the art of producing light from wood, ignited
in close vessels.
Many other attempts have been made to derive advantage from the
different ingredients of coal; but they are too obscure to merit
particular enumeration.
In the year 1808, Mr. MURDOCH presented to the Royal Society his account
of the application of gas-light, and was complimented with Count
ROMFORD’s medal for the same.
The following statement is taken from Mr. MURDOCH’s paper.
“The whole of the rooms of the cotton mill of Mr. LEE, at Manchester,
which is I believe the most extensive in the United Kingdom, as well as
its counting-houses and store-rooms, and the adjacent dwelling house of
Mr. LEE, are lighted with the gas from coal. The total quantity of light
used during the hours of burning has been ascertained, by a comparison
of shadows, (_see page 23_) to be about equal to the light which 2500
mould candles, of six to the pound, would give; each of the candles with
which the comparison was made consuming at the rate of 4-10ths of an
ounce (175 grains) of tallow per hour.
“The gas-burners are of two kinds: the one is upon the principle of the
Argand lamp, and resembles it in appearance; the other is a small curved
tube with a conical end, having three circular apertures or
perforations, of about a thirtieth of an inch in diameter, one at the
point of the cone, and two lateral ones, through which the gas issues,
forming three divergent jets of flame, somewhat like a fleur-de-lis. The
shape and general appearance of this tube has procured it, among the
workmen, the name of the cockspur burner.
“The number of burners employed in all the buildings amounts to 271
Argand, and 653 cockspurs, each of the former giving a light equal to
that of four candles of the description above-mentioned; and each of the
latter a light equal to two and a quarter of the same candles; making
therefore the total of the gas-light a little more than equal to that of
2500 candles, six to the pound. When thus regulated, the whole of the
above burners require an hourly supply of 1250 cubic feet of the gas
produced from cannel-coal; the superior quality and quantity of the gas
produced from that material having given it a decided preference in this
situation over every other coal, notwithstanding its higher price.
“The time during which the gas-light is used may, upon an average of the
whole year, be stated at least at two hours per day of 24 hours. In some
mills, where there is over work, it will be three hours; and in the few
where night work is still continued nearly 12 hours. But taking two
hours per day as the common average throughout the year, the consumption
in Messrs. Philips and Lee’s mill will be 1250 × 2 = 2500 cubic feet of
gas per day; to produce which 700 weight of cannel-coal is required in
the retort. The price of the best Wiggan cannel-coal (the sort used) is
13½_d._ per cwt. (22_s._ 6_d._ per ton) delivered at the mill, or say
about eight shillings for the seven hundred weight. Multiplying by the
number of working days in the year (313,) the annual consumption of coal
will be 110 tons, and its cost 125_l._
“About one-third of the above quantity, or say forty tons of good common
coal, value ten shillings per ton, is required for fuel to heat the
retorts, the annual amount of which is 20_l._
“The 110 tons of cannel-coal, when distilled, produce about 70 tons of
good coke, which is sold upon the spot at 1_s._ 4_d._ per cwt. and will
therefore amount annually to the sum of 93_l._
“The quantity of tar produced from each ton of cannel-coal is from 11 to
12 ale gallons, making a total annual produce of about 1250 ale gallons,
which not having been yet sold, it cannot yet be determined its value.
“The interest of the capital expended in the necessary apparatus and
buildings, together with what is considered as an ample allowance for
wear and tear, is stated by Mr. LEE at about 550_l._ per annum, in which
some allowance is made for this apparatus being made upon a scale
adequate to the supply of a still greater quantity of light, than he has
occasion to make use of.
“Mr. LEE is of opinion that the cost of attendance upon candles would be
as much, if not more, than upon the gas apparatus; so that, in forming
the comparison, nothing need be stated upon that score, on either side.
“The economical statement for one year, then, stands thus:
Cost of 110 tons of cannel coal £ 125
Ditto of 40 tons of common ditto, to carbonise 20
----
In all 145
----
Deduct the value of 70 tons of coke 93
The annual expenditure in coal, after deducting the value of the
coke, and without allowing any thing for the tar, is therefore 52
And the interest of capital sunk, and wear and tear of apparatus 550
Making the total expence of the gas apparatus per annum, about 600
“That of candles, to give the same light, would be about 2000_l._ For
each candle, consuming at the rate of 4-10ths of an ounce of tallow per
hour, the 2500 candles burning, upon an average of the year, two hours
per day, would, at one shilling per pound, the present price, amount to
nearly the sum of money above-mentioned.
“If the comparison were made upon an average of three hours per day, as
in most cases, would perhaps be nearer to the truth, and the tear and
wear remaining nearly the same as on the former case, the whole cost
would not exceed 650_l._ while that of the tallow would be 3000_l._”
Mr. ACKERMAN in this metropolis, has shown that the art of gas-light
illumination is not confined to great manufactories, but that its
advantages are equally applicable to those on a moderate scale. The
whole of Mr. ACKERMAN’s establishment, his public library, warehouse,
printing-offices and work-shops, together with his dwelling house, from
the kitchen to the drawing-room, has, for these four years past, been
lighted with gas, to the total exclusion of all other lights. The result
of the whole of this proceeding will be obvious from the following
letter:
To MR. ACCUM.
SIR,
“In answer to your request with regard to my gas-lights, which I now
have in my house, I take this mode of informing you, that I charge two
retorts with 240lbs. of coal, half cannel and half Newcastle, from
which I extract 1000 cubic feet of gas. To obtain this quantity of
gas, when the retorts are cold, I use from 100 to 110lb. of common
coals; but when they are in a working state, that is to say, when they
are once red hot, the carbonising fuel amounts to about 25lb. per
retort. The bulk of gas thus obtained supplies 40 Argand’s lamps, of
the large size, for four hours per night, during the long winter
evenings, together with eight Argand’s lamps and about 22 single
cockspur burners, for three hours per night: in addition to which my
printers employ 16 cockspur burners for ten hours per day to heat
their plates instead of charcoal fire. In the depth of winter we
charge two retorts per day: but, upon an average, we work 365 retorts
in 365 days.
Now 365 retorts containing 120lb. of coal each, make 43800lb. which is
equal to ten chaldrons of Newcastle and eight tons of cannel coal.
10 chaldrons of Newcastle coals, at 65s. make £ 32 10 0
8 tons of cannel coal,[15] (this coal is sold by weight)
at 100s. per ton 40 0 0
7 chaldrons of common coals for carbonising, at 55s. 19 5 0
To wages paid the servant for attending the gas apparatus 30 0 0
Interest of money sunk 30 0 0
The wear and tear of the gas-light apparatus I consider to
be equal to the wear and tear of lamps, candlesticks, &c.
employed for oil, tallow, &c. -----------
Total expence of the gas lights 151 15 0
DEDUCT
23 chaldrons of coke, at 60s. per chaldron 69
Ammoniacal liquor 5
Tar 6
Charcoal employed by the copper-plate printers to
heat their plates, which is now done with the gas-
light flame, cost, annua 25
Two chaldrons of coals _minus_ used as fuel, for
warming the house, since the adoption of the gas-
lights, at 65s. per chaldron 6 10
------ 111 10 0
----------
Nett expences of the gas-lights £ 40 5 0
----------
The lights used in my Establishment, prior to the gas-
lights, amounted annually to 160 0 0
My present system of lighting with gas costs, per ann. 40 5 0
----------
Balance in favor of the gas for one year £ 119 15 0
Such is the simple statement of my present system of lighting, the
brilliancy of which, when contrasted with our former lights, bears the
same comparison to them as a bright summer sun-shine does to a murky
November day: nor are we, as formerly, almost suffocated with the
effluvia of charcoal and fumes of candles and lamps. In addition to
this, the damage sustained by the spilling of oil and tallow upon
prints, drawings, books and paper, &c. amounted annually to upwards of
50l. All the workmen employed in my establishment consider their
gas-lights as the greatest blessing; and I have only to add, that the
light we now enjoy, were it to be produced by means of Argand’s lamps
or candles, would cost at least 350l. per annum.
I am, with respect,
Yours,
Strand, March 13,
1815.
R. ACKERMAN.”
[15] _Although cannel-coal sells at nearly double the price of
Newcastle coal, I use it in preference to the latter, because it
affords a larger portion of gas, and gives a much more brilliant
light._
Another manufacturer who was one of the first that adopted the use of
this method of illumination in the small way, and who gave a statement
of its advantages to the public, is Mr. COOK, a manufacturer of metal
toys, at Birmingham, a clear-headed, prudent man, not apt to be dazzled
by a fanciful speculation, but governed in his transactions by a simple
balance of profit and loss. There is a _naïveté_ in his own account of
the process which will amuse as well as instruct the reader.
“My apparatus is simply a small cast-iron pot, of about eight gallons,
with a cast-iron cover, which I lute to it with sand. Into this pot I
put my coal. I pass the gas through water into the gasometer or
reservoir, which holds about 400 gallons; and, by means of old
gun-barrels, convey it all round my shops. Now, from twenty or
twenty-five pounds of coal, I make perhaps six hundred gallons[16] of
gas; for, when my reservoir is full, we are forced to burn away the
overplus in waste, unless we have work to use it as it is made: but, in
general, we go on making and using it, so that I cannot tell to fifty or
a hundred gallons;--and, in fact, a great deal depends on the coals,
some coals making much more than others. These twenty-five pounds of
coal put into the retort, and say twenty-five pounds more to heat the
retort, which is more than it does take one time with another, but I am
willing to say the utmost, are worth four-pence per day. From this
four-pence we burn eighteen or twenty lights during the winter season.”
[16] A wine-gallon is equal to 231 cubic inches.
Thus are the candles which Mr. COOK used to employ, and which cost him
three shillings a day, entirely superseded. But, besides his expence in
candles, oil and cotton for soldering, used to cost him full 30_l._ a
year; which is entirely saved, as he now does all his soldering by the
gas flame only. For “in all trades in which the blow-pipe is used with
oil and cotton, or where charcoal is employed to produce a moderate
heat, the gas flame will be found much superior, both as to quickness
and neatness in the work: the flame is sharper, and is constantly ready
for use; while, with oil and cotton or charcoal, the workman is always
obliged to wait for his lamp or coal getting up; that is, till it is
sufficiently on fire to do his work. Thus, a great quantity of oil is
always burned away useless; but, with the gas, the moment the stop-cock
is turned, the lamp is ready, and not a moment is lost.” We must refer
to Mr. COOK’s letter for the details of expence, which he gives with
faithful minuteness, and always leaning to the side unfavourable to the
gas. The result of the whole is, that he saves 30_l._ out of the 50_l._
which his lights formerly cost him: and, when we consider that his
calculation allows the gas-lights to burn the whole year, and the
candles only twenty weeks, there can be little doubt, that the savings
in this case follow nearly the same proportion as in the former. If the
apparatus be erected even on a smaller scale, “the saving,” Mr. COOK
assures us, “will still be considerable: for the poor man, who lights
only six candles, or uses one lamp, if the apparatus is put up in the
cheapest way possible, will find it only cost him 10_l._ or 12_l._ which
he will nearly, if not quite, save the first year.”
Mr. ACKERMAN having, in this town, set the example of lighting his
establishment with gas, several other individuals soon followed the
attempt. The following statement will show, that this species of light
may be made use of with the greatest advantage, upon a still smaller
scale, where no great nicety with regard to the apparatus for procuring
gas is required. The following report I have received from Messrs.
LLOYD, of Queen Street, Southwark, thimble manufacturers and
whitesmiths, who have used the gas-light for soldering and other
purposes these five years past.
From 4 pecks or 1 bushel of coals, weighing 69lbs. for
which we now pay (1809) 1s. we produce 4¾ pecks of
coke and ½ peck of coal not carbonised remains in the
distilling pot, which together with the coke weighs
58lbs. 6 oz. value at 1s. per bushel 0 1 4
we procure 6lbs. 4 oz. of tar which we use as pith--it
saves us 0 1 0
----------
0 2 4
Deduct for coal 0 1 0
----------
Profit on coke and tar 0 1 0
----------
The gas yielded by the 4 pecks of coals in the pot, make
42 brilliant lights, which burn 7 hours. To keep 42
tallow candles which were formerly used in the manufactory
burning for the same time, required 7lbs. which at 1s. per
lb. cost 0 7 0
To this, add profits on coke and tar 0 1 0
----------
Gained out of every bushel of coal 0 8 0
----------
“The gas-burners made use of in our manufactory produce jets of flame,
which in our business, where much soldering with the blow-pipe must be
done, have a decided superiority over Argand’s lamps. We are not nice
concerning the quality of the gas--a great part of it is burned from the
gasometer, without allowing it to purify itself in the gasometer,
because our gasometer is not large enough to store up the whole quantity
of gas we want for use.”
THEORY OF THE PRODUCTION OF GAS-LIGHT, AND DESCRIPTION OF A PORTABLE
APPARATUS FOR EXHIBITING, IN THE SMALL WAY, THE GENERAL NATURE OF THIS
SPECIES OF LIGHT.
To obtain carburetted hidrogen, or coal-gas, from common pit-coal, and
to apply it for the purposes of illumination, the coal is introduced
into large iron cylinders, called retorts, to the apertures of which
iron pipes are adapted, terminating in a vessel, or vessels, destined to
purify and collect the gas. The retorts charged with coals and made
air-tight, are placed upon the fire, the action of which extricates the
gazeous products from the coals, together with an aqueous ammoniacal
vapour, and a tenaceous bituminous fluid, or tar, &c. The liquid
substances are conveyed into proper vessels, and the gazeous products
are conducted, by means of pipes, under the gasometer, where the gas is
again washed, and remains ready for use. There are also other pipes
leading from the gasometer, which branch out into smaller ramifications,
until they terminate at the places where the lights are wanted. The
extremities of the pipes have small apertures, out of which the gas
issues, and the streams of gas being lighted at those apertures burn
with a clear and steady flame as long as the supply of gas continues.
All the pipes which come from the gasometer are furnished at their
extremities with stop-cocks to regulate the admission of the gas. The
burners are formed in various ways, either a tube ending with a simple
orifice, at which the gas issues in a stream, and if once lighted will
continue to burn with the most steady and regular light imaginable, as
long as the gas is supplied; or two concentric tubes of brass, or
sheet-iron, are placed at a distance of a small fraction of an inch from
each other, and closed at the bottom. The gas which enters between these
cylinders, when lighted, forms an Argand lamp, which is supplied by an
internal and external current of air in the usual manner. Or the two
concentric tubes are closed at the top with a ring having small
perforations, out of which the gas alone can issue, thus forming
small distinct streams of light.
[Illustration]
The gas-apparatus, plate 2, will be found very convenient for
exhibiting, in the small way, the general nature of this new art of
illumination, whilst at the same time it may serve to ascertain, at a
trifling expence, the comparative value of different kinds of coals
intended to be employed for the production of this species of light, as
well as other occasional purposes connected with the gas-light system of
illumination.
It consists of three distinct apparatus:--namely, a portable furnace,
fig. 1, plate 2, by means of which the gas is prepared--fig. 2, a
purifyer, or condenser, which separates and purifies the products
obtained from the coal, so as to render the gas fit for the purpose of
illumination--fig. 3, a gasometer, or reservoir for receiving and
preserving the purified stock of gas, and from which it may be
transferred and distributed as occasion may require. The following
statement will explain more fully the general nature of this portable
chamber apparatus:--_a_, represents a cast iron retort, such as is used
for chemical operations in the small way. This retort rests upon a
tripod of hammered iron, placed upon the bars of the grate of the
chemical furnace. Into this retort the coals are put for furnishing the
gas. It is provided with a solid iron stopper ground air-tight into the
mouth of the retort, and the stopper is secured in its place by an iron
wedge passing over it in the centre; by means of which the mouth of the
retort when charged with coal is readily made air-tight, and the stopper
may easily be removed by knocking out the iron wedge. _b._ is a metal
pipe which conveys all the distillatory products from the retort into
the purifier fig. 2. This tube is bent at right angles at the extremity
where it enters the intermediate vessel fig. 2. The purifier fig. 2, is
divided into three compartments marked _c._ _d._ _e._ The first
compartment is filled with water, and by means of it an air-tight
communication is established with the retort which furnishes the gas.
The second compartment, _d_, contains a solution of caustic pot-ash
composed of about 2 parts of caustic pot-ash and 16 of water, or a
mixture of quick-lime and water of the consistence of very thin cream.
The object of this compartment is to separate the non-inflammable gases
and other products evolved during the distillation of the coal, from the
carburetted hidrogen or coal-gas, so as to render it fit for use. The
third compartment _e_ is left empty to receive the tar and other liquid
products. Into the first compartment _c_, all the gazeous and liquid
products are delivered, as they become evolved during the distillation,
by means of the pipe _b_. The compartment _d_, of the purifier, or
alcali vessel, is furnished with a wide perpendicular pipe, which serves
to make an air-tight communication with the retort, by allowing the tube
_b_, to pass readily through it. From the chamber _c_, the liquid and
gazeous products pass to the tar-chamber, or compartment _e_, by means
of the descending pipe _f_. The tar and other condensible substances are
therefore deposited at _e_, whilst the gazeous products alone ascend
from the tar-chamber _e_, by the pipe _g_, and down again the pipe _h_,
(which is closed at the top) into the compartment _d_, of the vessel or
purifier, fig. 2. The gas being thus made to pass from the compartment
_e_, up into the pipe _g_, and down the pipe _h_, (which is closed at
the top) into the purifier _d_, is brought into contact with the liquor
in that vessel, where it is opposed to a pressure in proportion to the
perpendicular height of the column of liquid which it contains. The
funnel in the compartment _c_, is considerably higher than the purifying
apparatus, it therefore allows the liquid which it contains, when
pressed upon by the gas, to ascend into it, without overflowing the
apparatus, and to descend again as the pressure diminishes--_i_ is
another wide-mouth funnel, by means of which the chamber _d_, is filled
with the alcaline solution, or mixture of lime and water. The carbonic
acid gas and sulphuretted hidrogen, evolved during the distillation of
the coal, are thus made to combine with the alcali or lime, in the
compartment _d_, of the purifier, forming carbonate and hidro-sulphuret
of lime. The carburetted hidrogen, being left more or less pure, is
conveyed through the pipe _k_, into the gasometer, fig. 3. The
communication of the purifier, fig. 2, with the gasometer, is made by
means of the well-known water-valve _l_, placed so that the
communicating tube _k_, may be easily removed at pleasure--_m_, is a
cock for drawing off the tar, &c. _n_, a gauge-cock for ascertaining the
height of the liquid in the chamber _d_. The gasometer, fig. 3, the
object of which is to store up the gas, consists of two principal
parts--namely, a large interior vessel designed to contain the gas, and
an outer cistern or vessel, of rather greater capacity, in which the
former is suspended, designed to contain the water by which the gas is
confined. The interior vessel which contains the gas is suspended by
chains or cords hung over pullies, to which weights are attached, so as
to nearly equipoise it. _o_ is a pipe, which communicates with the
water-valve _l_, and by means of which the gas passes from the purifier,
fig. 2, into the gasometer. The upper end of this pipe is covered, in
the manner of a hood, by a cylindrical vessel _p_, open at bottom, but
partially immersed beneath the surface of the water contained in the
outer cistern of the gasometer, and perforated round near the lower edge
with a number of small holes. The gas displaces the water from this
receiver _p_, and escapes through the small holes, rising in bubbles
through the water, so as to expose a large surface to its action, that
it may be properly washed, &c. After rising through the water the gas
enters the gasometer, which is suspended to move up and down by the
chains, pullies, and balance-weights, _q_. From the centre of the
gasometer a tube, _r_, descends, which includes a pipe, _s_, fixed
perpendicular from the bottom of the cistern. The fixed pipe _r_, forms
a guide to keep the gasometer always perpendicular. _t_ is also an iron
pipe made fast in the centre of the inner vessel, and communicates with
the upright tube, _s_, in the outer vessel. This contrivance obliges the
gas to pass into the pipe _t_, whilst it also serves to keep the
gasometer steady when nearly out of the outer cistern.
When the operation commences, the gasometer is sunk down nearly to a
level with the surface of the water in the outer cistern, and is
consequently filled with water; but as the gas enters, it rises up to
receive it. It is to be noted, that the balance-weights _q_ _q_, should
not be quite so heavy as the gasometer, in order that some pressure may
be exerted, to force the gas out of the burners with a proper jet. The
gas which issues from the retort enters the purifier as stated already,
and ascends the pipe _o_, into the vessel, _p_, from which it displaces
the water, and passes out at the small holes, as before described,
rising through the water into the gasometer, and raising it up: the gas
then passes away to the burners, _u_ _u_. In this manner the process
proceeds until the whole of the volatile products of the coal in the
retort is evaporated. The use of the gasometer is, to equalize the
emission of the gas which comes from the retort more quickly at some
time than others. When this happens, the interior vessel rises up to
receive it, and when the stream from the retort diminishes, the weight
of the gasometer expels its contents. When the process is finished, the
retort is suffered to cool, and its ground stopper is then removed to
replenish it with coal. The residue found in the retort is coke. _v_ _v_
are cocks to let off any liquid that may collect in the pipe _o_ or _t_;
for if the smallest portion of liquid were to obstruct the free passage
of the gas to the burners, the consequence would be, that the lights
would not burn steadily--they would, as it is called, _dance_, or become
extinguished. _x_ is the main stop-cock which communicates with the
burners--these, of course, may be placed as convenience may require. _z_
_z_ are two projecting parts in the top of the gasometer; they are
intended to receive the hood _p_, and the upper extremity of the pipe
_t_, so as to allow the gasometer to be wholly immersed into the
cistern. The wheels or pullies of the gasometer have a groove to allow
the links of the chain to pass freely.
In this apparatus there is no provision made for the unequal pressure
which the gas suffers, accordingly as the gasometer is more or less
immersed in water. It will be observed that, in this apparatus, the
weight of the interior vessel is constantly increasing, in proportion as
it fills with gas, and rises out of the water, and consequently, if a
constant, uniform, counterpoising weight, equal only to that of the
gasometer in the first moment of its rise, be employed, the gas becomes
gradually more and more compressed by that part of the weight of the
gasometer which is not counterpoised, and if its pressure or quantity be
then estimated by the bulk which it occupies, without making allowance
for the increasing pressure, a material error must arise, and this, in
the large way, would give rise to insurmountable difficulties with
regard to the regulation of the size of the flames; which could not be
rendered uniform.
Suppose the cistern or exterior vessel full of water, and the gasometer
partly filled with gas and partly with water, it is evident that the
balance-weight may be so adjusted, as to occasion an exact equilibrium,
so that the external air shall not tend to enter into the gasometer nor
the gas to escape from it; and in this case the water will stand exactly
at the same level both within the gasometer and within the outer
cistern. On the contrary, if the balance-weights be diminished, the
gasometer will then press downwards from its own gravity, and the water
will stand lower in the gasometer than it does in the cistern; in this
case, the included air or gas will suffer a degree of compression above
that experienced by the external air, exactly proportioned to the weight
of a column of water, equal to the difference of the external and
internal surfaces of the water.
To compensate for this increasing weight of the gasometer, and render a
scale of equal graduations accurate, some have ingeniously adopted the
plan of a spiral pulley to the chain, which has the effect of gradually
avoiding the evil, but the best way of accomplishing it will be stated
hereafter.
With regard to the philosophy or the production of coal-gas, it proves
that pit-coal contains solid hidrogen, carbon, and oxigen. When the
intensity of the heat has reached a certain degree, a part of the carbon
unites with part of the oxigen and produces carbonic acid, which by
means of caloric is melted into the gazeous state and forms carbonic
acid gas; at the same time, part of the hidrogen of the coal combines
with another portion of carbon and caloric, and forms the carburetted
hidrogen gas, which varies considerably in its constitution, according
to the circumstances under which it is produced; a portion of olifiant
gas, carbonic oxid, hidrogen, and sulphuretted hidrogen, is also
produced during the process. The quantities of these products vary
according to the nature of the coal employed in the process.
Pit-coal is not the only substance which affords carburetted hydrogen;
this gazeous fluid may be obtained in a great variety of ways, and with
very considerable differences in specific gravity and proportion of
ingredients.
It is found plentifully native or ready formed on the surface of
stagnant waters, marshes, wet ditches, &c. through which, if examined
closely, large bubbles will be seen to rise in hot weather, and may be
increased at pleasure by stirring the bottom or mud with a stick.
In close still evenings if a lighted candle is held over the surface,
flashes of blue lambent flame may sometimes be perceived spreading to a
considerable distance. All that is not fabulous concerning the _ignis
fatuus_ is probably derived from this source. This species of gas is
termed for distinction the carburetted hydrogen of marshes. In the
purest form in which it can be collected it is mixed with about 20 per
cent. of azot or nitrogen.
To procure the gas for the purpose of philosophical amusement, fill a
wide-mouthed bottle with the water of the ditch, and keep it inverted
therein with a large funnel in its neck, then with a stick stir the mud
at the bottom just under the funnel, so as to cause the bubbles of air
which rise from the mud to enter into the bottle; when by thus stirring
the mud in various places, the air may be catched in the bottle.
Carburetted hidrogen gas is also given out very abundantly by all kinds
of vegetable matter when subjected to a scorching heat sufficient to
decompose them. When heated in close vessels much more gas is obtained
than when burnt in the open air. If moistened charcoal be put into an
earthen retort and heat be applied till the retort becomes ignited; gas
will be evolved, consisting partly of carbonic acid, and partly of
carburetted hidrogen. A gas of similar properties is obtained by causing
steam to pass through a tube filled with red-hot charcoal; by passing
spirit of wine, or camphor, through red-hot tubes; by distilling oils,
wood, bones, wax and tallow, or any animal or vegetable body whatever.
Indeed it would be endless to enumerate the various sources of this
gazeous fluid. A most curious variety of carburetted hidrogen gas has
been discovered by the associated Dutch chemists (VAN DIEMAN,
TROOSTWYCK, and others) which is procured from ether or alcohol, and has
the remarkable property of generating a heavy oil when in contact with
chlorine gas. Hence it has been termed oily carburetted hidrogen, or
olifiant gas--it consists of carburetted hydrogen, supersaturated with
carbon. The oil generated is heavier than water, whitish, and
semi-transparent. By keeping, it becomes yellow and limpid; its smell is
highly fragrant and penetrating--its taste somewhat sweet--it is partly
soluble in water, imparting to it, its peculiar smell. A portion of this
gas always accompanies the common carburetted hidrogen obtained from
coal, and those sorts of coal that afford the largest quantity of it are
best suited for the production of gas-light.
The nature of carburetted hidrogen obtained from coal varies
considerably according to the conditions under which it is obtained. The
first part is always much heavier than the last, though still lighter
than common air, and holds in solution a portion of oil, for on standing
for some time over water it becomes lighter, and is found to require
less oxygen for saturation than before. The oil which it held suspended,
then becomes precipitated. The average specific gravity of the first and
last gas mixed, which may be taken as an average of the whole specific
gravity is to that of common air as 2 to 3--112lb. of common cannel
coal produce at its _minimum_, from 350 to 360 cubic feet of carburetted
hidrogen gas; but the same quantity of the best Newcastle coal, that is
to say, such as coke, which, when laid on the fire readily undergoes a
kind of semi-fusion, and sends out brilliant streams of flame, produces
upon an average from 300 to 360 cubic feet of this gazeous fluid,
besides a large portion of sulphuretted hidrogen, carbonic oxid and
carbonic acid. Half a cubic foot of this carburetted hidrogen, fresh
prepared, that is to say, holding in solution or suspension, a portion
of the essential oil, which is generated during the evolution of the
gas, is equal in illuminating power to from 170 to 180 grains of tallow,
(being the quantity consumed by a candle six to the pound in one hour.)
Now, one pound avoirdupoise is equal to 7000 grains, and consequently
one pound of candles of six in the pound, burning one at a time in
succession, would last (if we take 175 grains of tallow to be consumed
in an hour) 7000/175 = 40 hours. To produce the same light we must burn
one half of a cubic foot of coal-gas per hour; therefore, one-half
multiplied by forty hours is equal to twenty cubic feet of gas in 40
hours, consequently equal to one pound of candles, six to the pound,
provided they were burnt one after another. One hundred and twelve
pounds of cannel-coal, produce, at its _minimum_, three hundred and
fifty cubic feet of gas; and are equal to three hundred and fifty,
divided by twenty, which last is equivalent to one pound of tallow,
making one hundred and twelve pounds of cannel-coal, equal to 350/20 =
17½lbs. of tallow. Further, one hundred and twelve pounds of
cannel-coal, divided by seventeen and a half of tallow make six and
four-tenths of cannel-coal, equal to one pound of tallow.
With regard to Newcastle coals[17], it may be stated that one chaldron
of Wall’s-End coal may be made to produce in the large way upwards of
11,000 cubic feet of crude gas; which, when properly purified,
diminishes to nearly 10,000 cubic feet.
[17] One chaldron of Newcastle coal weighs from 2850 to upwards of
2978lb.
The production of carburetted hydrogen, both with regard to quantity and
quality from the same kind of coal depends much upon the degree of
temperature employed in the distillatory process. If the tar and oil
produced during the evolution of the gas in its nascent state, be made
to come in contact with the sides of the red hot retorts, or if it be
made to pass through an iron cylinder or other vessel heated red hot, a
large portion becomes decomposed into carburetted hydrogen gas and
olifiant gas, and thus a much larger quantity of gas is produced than
would be obtained without such precaution from the same quantity of
coal.[18]
[18] One pound of coal-tar produces 15 cubic feet of carburetted
hidrogen abounding in olifiant gas.
The distillation of the coal, (if gas be the chief object) should
therefore not be carried on too rapidly. Most of the retorts used in the
large way, are calculated for containing about one hundred weight of
coal, and in general, when previously heated, produce from two and
one-half to three cubic feet of gas, in four hours for each pound of
coal they contain; but when the layer of coals in them does not exceed
four inches in depth, three and one-half to four feet of gas may be
obtained in the same time.
The retorts best calculated for large gas-light works are seven or eight
foot long (without the mouth-piece) and twelve inches in diameter,
tapering down to ten inches--if they are larger the coal which they
contain cannot be heated properly. The advantages that may be derived
from the circumstances before stated are of greater value in the
gas-light manufacture than is often imagined, and the quantity as well
as the quality of the gas is very much influenced by such circumstances.
If coal be distilled with a very low red heat scarcely observable by
daylight, the gas produced gives a feeble light--if the temperature be
increased so that the distillatory vessel is of a dull redness, the
light is more brilliant and of a better colour--if a bright or
cherry-red heat be employed the gas produced, burns with a brilliant
white flame, and if the heat be increased so far that the retort is
almost white hot, and consequently in danger of melting, the gas given
out, has little illuminating power, and burns with a clear blueish
flame;[19] or if the coal abounds in pyrites or sulphuret of iron, as is
sometimes the case with Newcastle coal, a large quantity of sulphuretted
hidrogen is likewise evolved, which although it increases the
illuminating power of the coal-gas, has the capital disadvantage, of
producing an intolerable suffocating odour, when the gas is burnt which
is particularly perceptible in low rooms illuminated with such gas.
[19] It is chiefly a mixture of carbonic oxid, and hydrogen gas.
These observations also apply to the distillation of tar, which when
distilled either in a vaporous or nascent state, during its first
production from coal in the ordinary process, or if it be submitted to a
second distillation, mingled with a fresh portion of pit-coal, a
practice usually had recourse to when this product cannot be disposed of
more advantageously. The best depth of coal in the retort for procuring
excellent gas, and at the same time for yielding the greatest quantity
from the same weight in the shortest possible time, is about six inches.
The brightness of the coal-gas flame is rather diminished when the gas
has been long kept over water, and hence for illumination it should be
used as soon as prepared, but of course properly purified.
The quantity of gas taken up by water is affected by temperature,
because the temperature increases its elasticity; the quantity of gas
absorbed, diminishes as the temperature increases, and increases as the
temperature diminishes. ½7 part of its own bulk of pure coal-gas is
absorbed by the water over which it is confined in the gazometer.
The chemical constitution of this gazeous fluid is best ascertained by
burning it in a vessel of oxygen gas, over lime-water in a pneumatic
reservoir, by means of a bladder and bent brass pipe. Two products are
then obtained, viz. water and carbonic acid. That water is produced, may
be shown by burning a very small stream of the gas in a long
funnel-shaped tube open at both ends. The formation of carbonic acid is
evinced, by the copious precipitation of the lime-water in the foregoing
experiment.
If carburetted hydrogen be mixed with a sufficient quantity of oxygen
gas or common air and fired by the electric spark, or by any other
method, an explosion takes place more or less violent according to the
quantity of carbonaceous matter condensed in the hydrocarbonat; and the
remaining gas consists of carbonic acid, together with any unconsumed
gas, or excess of oxygen, whilst the water condenses in drops on the
sides of the vessel. A few cubic inches of the mixed airs is as much as
can be conveniently managed at a single explosion; and when any portion
of olefiant gas is present, even this quantity will endanger very thick
glass jars. A very vivid red flame appears at the moment of the
explosion, and a great enlargement takes place in an instant, after
which the bulk is suddenly reduced to much less than the original
quantity. When the carbonic acid is absorbed by lime-water, if the
gasses have been properly proportioned, no gazeous residue is left,
except accidental impurities. Though carburetted hydrogen gas, is
sometimes naturally produced in coal-mines, and occasionally mixes with
common air, producing dreadful explosions, yet when coal-gas is mixed
with common air, it does not explode unless the gas be to the air as 1
to 10 nearly. Such are the leading chemical habitudes of this gazeous
product. The varieties of carburetted hydrogen gas all agree in being
inflammable; but they possess this property in various degrees, as is
evinced by the variable brightness of the flame which they yield when
set on fire.
“Messrs. SOBOLEWSKY and HORRER, of St. Petersburgh, have employed wood
for the purpose of producing carburetted hydrogen gas. The pyroligneous
acid obtained in this operation, when freed from the empyreumatic oil
with which it is mixed, becomes acetous acid, and is applicable to all
the uses of vinegar. A cubic cord of wood equal to 2.133 French metres
(a metre being rather more than an English yard), yields 255 Paris
pounds of charcoal, and 70 buckets of acid. The latter gives 30 pounds
of tar, after the extraction of it 50 buckets of good vinegar remain.
The same quantity of wood furnishes 50,000 cubic feet of gas, sufficient
for the supply of 4000 lamps for five hours.”[20]
[20] See Repository of Arts, Vol. XI. No. 36, p. 341.
UTILITY OF THE GAS-LIGHT ILLUMINATION, WITH REGARD TO PUBLIC AND PRIVATE
ECONOMY.
From what has been stated in the preceding pages it becomes obvious,
that a substance yielding an artificial light may be obtained from
common coal in immense quantities. The attempt to derive advantage from
so valuable a discovery is surely no idle speculation. Let us therefore
now consider to what objects of public and private utility this mode of
procuring light may be applied with effect. It is obvious that coal-gas
may be preserved in a reservoir for any length of time and that it may
be conveyed by means of tubes to any distance flowing equably and
regularly like water. Those, indeed, who have not seen the contrivance
will find it difficult to imagine with what ease it is managed. The gas
may be distributed through an infinity of ramifications of tubes with
the utmost facility. Near the termination of each of the tubes through
which it flows, it is confined by a valve or stop-cock, upon turning
which, when required to be lighted, it flows out in an equable stream
and ascends by its specific levity. There is nothing to indicate its
presence; no noise at the opening of the stop-cock or valve--no
disturbance in the transparency of the atmosphere--it instantly bursts
on the approach of a lighted taper, into a brilliant, noiseless, steady
and beautiful flame. Its purity is attested by its not blacking or
soiling in the least degree the metallic orifice from which it issues,
nor even a sheet of white paper, or polished surface brought in contact
with it. There is no escape of combustible matter unconsumed, which is
so great a nuisance in all our common lights. The products of the
combustion are water and carbonic acid gas[21]. The accurate and elegant
experiments of Dr. W. HENRY have shewn in the most satisfactory manner,
that considerably less carbonic acid is produced by the flame of
coal-gas, than by that of oil, tallow, or wax[22], which sufficiently
refutes the absurd notions that have been circulated respecting the
pernicious effects of gas-lights. But if the gas from Newcastle coal is
badly prepared, or not deprived of the portion of sulphuretted hydrogen,
which it usually contains, it then emits fiery sparks and produces a
portion of sulphureous acid by virtue of the union of the oxygen of the
air with the sulphur dissolved in the gas, the consequence of which is,
a suffocating odour, which is particularly observable in the higher
stratum of the air of apartments in which the gas is burnt. Such gas
likewise tarnishes all metallic bodies--it discolours the paintings
effected with metallic oxids, and always produces a suffocating odour
very noxious to health. It is freed from the sulphuretted hydrogen and
may be rendered fit for illumination by passing it repeatedly through
very dilute solutions of sub-acetate of lead, green sulphate of iron,
quicklime and water, or hyper-oxymuriate of lime.
[21] The water (which passes off in imperceptible vapour) is generated
by part of the oxygen of the air uniting with part of the hydrogen,
which forms the great bulk of the coal-gas: and the carbonic acid gas
is produced by the union of another portion of the oxygen uniting with
the smaller portion of carbon, which is the other component part of
the coal-gas.
[22] 100 Cubic inches of carburetted hydrogen from coal, require for
burning 220 cubic inches of oxygen and produce 100 cubic inches of
carbonic acid--100 cubic inches of the same gas obtained from wax,
require for burning 280 cubic inches of oxygen and produce 137 cubic
inches of carbonic acid--100 cubic inches of the same gas procured
from lamp-oil, require 190 cubic inches of oxygen for burning, and
produce 124 cubic inches of carbonic acid.
The following lines relating to the salubrity of the gas-light
illumination are copied from Mr. Lee’s evidence in the House of
Commons, when examined on that subject.
Question--“Is the health of your manufacturers at all affected by the
use of gas?--Answer--Not in the least, or I would not have adopted it.
I believe I explained to the Committee, that I used the gas-lights in
my own house first.”
Q. “You have not seen the smallest alteration in the health of your
workmen?--A. Not in the least, for had I seen it, it would have been a
fatal objection to it.”
Q. “And you say the same in regard to the use of the gas-lights in
your own family?--A. Certainly I do.”
As to the brilliancy of the flame, an appeal may be made to every one
who has witnessed the gas-light illumination, whether it be not superior
to the best wax candle-light, or the light of Argand’s lamps.
It may be described as a rich compact flame, burning with a white and
agreeable light. It is also perfectly steady, when the flame is limited
to a moderate size: in large masses, it is subject to that undulation
which is common to it with all flames of certain dimensions, and is
caused by the agitation of the surrounding atmosphere. The gas flame is
entirely free from smell. The coal-gas itself certainly has a
disagreeable foetid odour before it is burnt, so has the vapour of wax,
oil, and tallow, as it comes from a lamp or candle newly blown out. This
concession proves nothing against the flame of gas which is perfectly
inodorous, a white handkerchief, passed repeatedly through it and
applied to the nose, excites no odour.
Another peculiar advantage of the gas flame is, that it may be applied
in any direction we please, as there is nothing to spill and the gas is
propelled by a certain force which is always the same, it will burn
equally well in an almost horizontal as in an upright position; and we
can thus obviate two great objections to all our artificial lights, that
their least luminous end is directed downwards where the light is
generally most wanted, and that a shade is cast below by the stand or
support of the combustible matter.
The size, shape and intensity of the gas-flame may be regulated by
simply turning a stop-cock which supplies the gas to the burner. It may
at command be made to burn with an intensity sufficient to illuminate
every corner of a room, or so low and dim as barely to be perceived. It
is unnecessary to point out how valuable such lights may be in
nurseries, stables, warehouses, in the chambers of the sick, &c.
From the facility with which the gas-flame can be conveyed in any
direction, from the diversified application, size and shape which the
flame can be made to assume, there is no other kind of light so well
calculated for being made the subject of splendid illuminations.
Where lustres are required in the middle of a room, the best mode of
conducting the gas to the chandelier, is to pass the gas-pipe through
the ceiling from the room above, immediately over the lustre. This can
be easily done without injury to the apartment.
Where side-lights and chandeliers are required the tubes need never
appear in sight, but may be concealed in the wall or floor of the
house. When transparencies are wanted as decorations for halls, lobbies,
&c. more than light, recesses may be filled with different coloured
_media_, or paintings, and any intensity of light may be thrown on the
object.
If a number of minute holes are made in the end of a gas pipe, it forms
as many _jets de feu_, which have a very brilliant appearance; these may
sometimes be placed in the focus of a parabolic reflector. In cases
where the light is required to be thrown to a distance, other burners
are constructed upon the same principle as the Argand lamp, forming a
cylinder of flame, and admitting a current of air both to the inside and
outside.
On comparing the flame of a gas-light with the flame of a candle
whatever its size may be, it appears just as yellow and dull as the
flame of a common lamp appears when compared with that of a lamp of
Argand. The beautiful whiteness of gas-light never fails to excite the
surprize and admiration of those who behold it for the first time.
A large edifice or manufactory lighted by gas, contrasted with one of
the same kind lighted by candles or lamps, resembles a street on the
night of a general illumination, compared with the glimmering light of
its ordinary parish lamps.
The intensity of one of the parish gas-light lamps, now exhibited in the
streets of this metropolis, will bear ample testimony of this assertion;
the light of the parish gas-lamps, is to the intensity of the parish oil
lamps as 1 to 12.
One of the most obvious applications of the gas-light illumination
unquestionably consists in lighting streets, shops and houses; and let
it be observed that as this is found safe and economical, it proves all
that the most ardent friends of the gas-light system can desire. For in
contending with the common mode of lighting the streets and shops, the
new lights must beat out of the market the cheapest of all artificial
lights; and as it has succeeded in doing this it shews in the most
satisfactory point of view, the prodigious advantages of gas-lights when
compared with the materials of tallow and oil.
The original expence of laying the pipes for conveying the gas, together
with the cost of the machinery, is all that is required; the preparation
of the gas being itself a lucrative process, no doubt will pay all its
expences besides the interest of capital, and leave a surplus of profit.
Indeed the application of the coal-gas, as a substitute for tallow and
oil, to illuminate houses, shops, &c. is no longer problematical, a
considerable extent of this capital, together with numerous shops and
houses being already supplied with this species of light.[23]
[23] The Liberty of Norton Falgate, as far as Bishopgate-street, is
lighted with gas-light, from the Chartered Company’s station at Norton
Falgate; and gas-light pipes are laid from that station as far as the
west end of Cheapside, and in all the streets north of that great
thoroughfare.
In the West end of the Town, the main pipes for supplying the streets
and houses with light from the Gas-Light Company, extend through the
most eligible parts; from their Establishment in Peter-street,
Westminster, along the line from Pall Mall to Temple-bar, compleatly
surrounding the parish of St. Martin’s in the Field. Main pipes are
also placed in the Hay-market, Coventry-street, Long-Acre, St.
Martin’s-lane; and in the principal parts of the parishes of St. James
and St. Ann.
In the East end of the metropolis, the gas-light _mains_ extend from
Cornhill to St. Paul’s, Wood-street, Fore-street, &c.--Consent has
also been given to the incorporated Gas-Light Company for laying their
pipes in the parish of St. Stephen’s in the Field; St. Paul
Covent-garden; St. Mary-le-Strand; St. Clement Danes; St. George’s,
Bloomsbury; St. Giles’s in the Fields; St. Andrew’s, Holborn, above
the bars; part of the parish of St. Mary-la-bonne; besides several
other districts, comprehending the whole of the city and suburbs of
Westminster.
Enough therefore, has been done to prove the possibility of lighting
houses, and streets, with gas, which would have been regarded twenty
years ago as an extravagant paradox.[24]
[24] I am informed by Mr. CLEGG, the engineer of the Chartered
Gas-Light Company, under whose direction the new system of lighting is
carried on, that the total length of pipe laid down, as mains, in the
streets of London amounts already to nearly 15 miles.
In the Eastern part of London, the same Company is engaged to lay
their pipes in the principal parts of Whitechapel, Spitalfields, St.
Luke’s, and the adjoining neighbourhood.
One part of the city of London, extending from Temple-bar to the West
end of Cheapside; from Newgate-street to Holborn Bars, together with
the intervening streets, is also provided with pipes laid down by
another gas-light association, who have opened a new Establishment in
Water-lane, Fleet-street, but are unconnected with the Chartered
Company. A third company is projected in Southwark, and a fourth in
the Eastern district of London, creating by a rivalry of interest,
that laudable competition which always proves beneficial to the public
at large, and which cannot fail to accelerate the progress of this new
art of procuring light.
The Church of St. John the Evangelist in this metropolis has been
illuminated with gas-lights for upwards of two years: the lights
employed in this edifice is equal to 360 tallow candles eight to the
pound. The avenues to the House of Lords and House of Commons,
Westminster-hall, Westminster-bridge; the house and offices of the
Speaker of the House of Commons, the Mansion-house, and many other
places, deserve to be named, as having already adopted this species of
illumination.
Another advantageous application of the gas-light must be the supplying
of light-houses.
From the splendour and distinguishing forms which the gas-light flame is
capable of assuming, no light is better calculated for signal-lights
than this. By means of one single furnace as much gas might readily be
procured as would furnish a flame of sufficient intensity, during the
longest winter night, exceeding in brilliancy or intensity of light any
light-house in Britain or elsewhere.
If every light-house round this island were possessed of a gas-light
furnace, one-half part of the enormous expence which they at present
require would furnish a much more brilliant light. The cheapness of this
light and its efficacy for the purpose, would soon multiply the number
of light-houses, and thus most essentially contribute to the security of
navigation on our coast. The gas may be made to issue from tubes by long
narrow slips, and a surface of flame produced of any given dimensions,
and free from all smoke that would obscure the reflectors.
The ease with which the largest gas-light flame is instantly
extinguished by shutting the stop-cock, and the readiness with which a
long line of gas catches fire by applying a lighted taper to one
extremity, are properties that cannot fail to recommend it for the
purposes of telegraphic communications by night. Another application of
the gas unquestionably might be the lighting of barracks, arsenals,
dock-yards, and other establishments where much light is wanted in a
small place.
The annual expence of lighting the barracks of Great Britain is said to
fall little short of 50,000l. a small part of which on the new plan,
would supply them with a much purer and safer light.
The uses of the gas-lights already enumerated must of themselves,
justify us in attaching great importance to the discovery, and if
reduced to practice all over the kingdom, would employ a large capital
in a way the most advantageous and productive. But the utility of this
light will be almost indefinitely increased to the use of private
families. That such an application is practicable, in all towns of Great
Britain, is obvious, from what has been done already, and that it would
be highly economical and ornamental, there can be little doubt.
By means of gas we may have a pure and agreeable light at command in
every room of our house, just as we have the command of water, with this
singular advantage, that these lights may burn for hours within an inch
of the most combustible substance without danger, because they neither
can burn down like a candle nor emit sparks. These properties make the
gas-lights a most desirable light on board our ships of war, where
severe regulations are necessary to prevent danger from fire, which
after all are frequently evaded. The gas-light might be used in the
store-rooms, and even in the powder magazine, and the captain would
completely command the supply of light by the possession of the key
which opens and shuts the stop-cock. A small apparatus which may be
erected at a trifling expence would be sufficient for that purpose.
In shops, counting-houses, and public offices, the advantages are a
white light, nearly equal to day-light, a warmth which almost supersedes
the use of fires, a total absence of smoke, smell, and vapour, and great
economy of labour.
The heat produced by gas-lights must be observed by every one who has
had an opportunity of attending to it in the most superficial manner,
and the reason why gas-lights produce more heat than oil or candle-light
will not appear strange to our chemical readers (and who is there now
that does not know something of chemistry?) when it is considered that
the gas-light flame condenses more air than the flame of oil and tallow,
and consequently must produce more heat.
The flame of gas may be produced in so large a surface, as to be applied
to heat the most spacious apartments as well as to light them.
If the gas is made to issue by a circular rim of about twelve inches
diameter; it forms a sort of an Argand lamp on a great scale, and it is
manifest that a circumference of three feet of flame will heat the air
very rapidly, and with such uniformity that we need no longer be exposed
to the partial heating occasioned by the strong draft of a large fire. A
lamp of this description in the centre of a large room, with a very
small fire to secure a gradual renewal of the air would enable us to
enjoy the most healthful and agreeable temperature.
From trials made on this subject, I am enabled to state, that three
Argand’s lamps, consuming five cubic feet of gas per hour, are
sufficient to keep a room 10 feet square at a temperature of 55° Fahr.
when the air without doors has a temperature of freezing.[25]
[25] Mr. DALTON’s method of ascertaining the comparative quantity or
effects of heat evolved during the combustion of different inflammable
gases, and other substances capable of burning with flame, as stated
in his System of Chemistry, vol. I. p. 76, deserves to be recommended
to those who are more immediately interested in this subject. The
process, which is simple, easy, and accurate, is as follows:
Take a bladder of any size, (let us suppose for the sake of
illustration, the bladder to hold or to be equal in capacity to 30,000
grains of water,) and having furnished it with a stop-cock and a small
jet pipe, fill it with the combustible gas the heating power of which
is to be tried. Take also a tinned iron vessel with a concave bottom
of the same capacity, pour into it as much water as will make the
vessel and water together equal to the above stated bulk of water in
the bladder, viz. 30,000 grains. This being done, set fire to the gas
at the orifice of the pipe, and bring the point of the flame under the
bottom of the tinned vessel, and suffer it to burn there, by squeezing
the bladder till the whole of the gas is consumed. The increase of
temperature of the water in the tinned vessel being carefully noticed
before and after the experiment, gives very accurately the heating
power of the given bulk of the inflammable gas.
It was thus proved that--
Olefiant gas raises an equal volume of water 14°
Carburetted hidrogen, or coal gas 10
Carbonic oxid 4
Hidrogen 5
Spermaceti oil 10 grains burnt in a lamp raised
30,000 grains of water 5
Tallow 5
Wax 5,75
Oil of turpentine 3
Spirit of wine 2
In all processes of the arts where a moderate heat is wanted the
gas-light flame will be found very advantageous--even on a large scale
this flame may be used with profit. It possesses advantages which cannot
be obtained from flaming fuel, where much nicety is required; because no
fuel can be managed like the flame of coal-gas. For it is well known,
that when too little air be given to flaming fuel it produces no flame,
but sooty vapour; and if too much air be admitted to make those vapours
break out into flame, the heat is often too violent. It is a fact, that
flame, when produced in great quantity, and made to burn violently, by
mixing with a proper portion of fresh air, driving it on the subject,
and throwing it into whirls and eddies, thereby mixing the air with
every part of the hot vapour, produces a very intense heat.
The great power of a gas-flame does not appear when we try small
quantities of it, and allow it to burn quietly, because the air is
not intimately brought into contact with it, but acts only on the
outside; and the quantity of burning matter in the surface of a small
flame is too minute to produce much effect.
[Illustration]
But when the flame is produced in large quantity and is freely brought
forward into contact and agitated with air, its power to heat bodies is
immensely increased. It is therefore peculiarly proper for heating large
quantities of matter to a violent degree, especially if the contact of
solid fuel with such matter is inconvenient.
As the gas-flame may be made to assume any shape and intensity, and as
there is nothing to spill, it may be exhibited under such variety of
forms and designs, as cannot fail to give rise to the most tasteful
ornamental illumination.
PLATES III. IV. and V. exhibit such designs of different kinds of
gas-lamps, chandeliers, lustres, candelabras, &c. as are already in use
in this Metropolis.
PLATE III. fig. 1, represents a _Rod Lamp_. The gas passes through the
rod _a_, to the Argand burner, which is surrounded by a cylindrical
chimney, _c_, swelling out at the lower extremity. The construction of
the Argand burner we have mentioned already, _p._ 78.
In all the gas-light burners, constructed on Argand’s plan, care should
be taken that the flame be in contact with the air on all sides, and
that the current of air be directed towards the upper extremity of the
flame. This may be effected by causing a current of air to rise up
perpendicular from the bottom of the chimney glass, and to pass out
again through the contracted part, or upper extremity of the chimney;
but no other current of air should ever be permitted to come near the
gas-flame, or enter the glass chimney which covers or defends the light;
for if more air be permitted to mix with the flame than is sufficient
for the compleat combustion of the coal-gas, it necessarily diminishes
the heat, and consequently reduces the quantity of light.
Fig. 2. _A Rod Gas Lamp, with branches._ The gas passes through the
hollow rod, _a_, and part of the hollow branch, _b_, to the burner of
the lamp. The cylindrical shaped glass, _c_, exhibited in this figure,
is not so well adapted for the compleat combustion of coal-gas, as the
belly-shaped chimney, _c_, represented in fig. 1, 3, 5, 6, because the
ascending current of fresh air is not turned out of its perpendicular
course, and thrown immediately in a concentrated state, into the upper
part of the flame where the combustion of the gas is less perfect. The
exterior current of air which enters at the bottom into the lamp, rises
merely with a velocity proportioned to the length of the cylinder, and
to the rarefaction of the air in the same, but without being propelled
to the apex of the flame, as it should do, and is made to do, in the
bellied glass adapted to the lamp, fig. 1.
Fig. 3. _A Bracket Lamp._ _a_, the tube which conveys the gas to the
burner; _b_, the stop-cock of the tube.
Fig. 4. _A Pendent Rod Lamp_; in which the gas is supposed to come from
a pipe above, through the ceiling, into the pipe, _a_, to supply the
burners. The tulip-shaped chimney, _b_, of this lamp, is likewise ill
adapted for gas-light burners.
Fig. 5. _A pendent double-bracket Lamp._ The gas passing through the
perpendicular tube, _a_, into the brackets, _b_ _b_; _c_ shows the
Argand burner.
Fig. 6. _A swing Bracket Lamp._ _a_, the gas-pipe with its stop-cock;
_b_, a brass ball, communicating with the pipe, _a_; _c_, the conducting
tube, ground air-tight into the ball, _b_, and communicating with the
burner of the lamp, so as to allow it to have an horizontal motion.
Fig. 7. Shews the construction of the ball _b_, and pipe, _c_, of the
lamp, fig. 6.
Fig. 8. _A Swing Cockspur Lamp_, constructed upon the same plan as fig.
6. These two lamps are very convenient for desks in counting-houses, &c.
Fig. 9. A stop-cock with ball and socket, which, when adapted to a
gas-light pipe, allows it to have an universal motion, so that the light
may be turned in any direction.
Fig. 10. Section of the stop-cock, with ball and socket.
Fig. 11. Shows the ball and socket, fig. 9, in perspective.
[Illustration]
PLATE IV,[26] fig. 1. _A Candelabrum_; the gas pipe ascending from
the floor of the apartment, through the column _a_, and terminating in
the burner of the lamp.
[26] The gas-lamps exhibited in this plate, are employed in the
library, counting-house, warehouse, and offices of Mr. ACKERMAN, and,
by whose permission, they are copied on this occasion.
Fig. 2. _A fancy pendent Cockspur Lamp._ The gas being transmitted to
the burners, _c_ _c_, by means of the pipe, _a_.
Fig. 3. _A Pedestal Argand Lamp._ _a_, the pipe and stop-cock, which
transmits to, and shuts off the gas from the burner of the lamp.
Fig. 4. _A Pedestal Cockspur Lamp._ _a_, the stop-cock and gas-pipe.
Fig. 5. _A fancy bracket Cockspur Lamp_, intended merely to show that
the coal-gas, as it passes to the burner, is perfectly devoid of colour,
and invisible. _a_ is a glass vessel furnished at its orifice with a
brass cap, _c_, and perforated ball, out of which the gas-flame
proceeds. _b_, the pipe which conveys the gas into the glass vessel,
_a_.
Fig. 6. _A Bracket Argand Lamp._ _a_ and _b_, the gas pipe communicating
with the burner.
Fig. 7 and 8. _A Horizontal Bracket Lamp._ _a_, the gas pipe, supposed
to be concealed in the ceiling. _b_, the communicating pipe, which,
together with _c_, branches out at right angles at _d_ _d_. _e_ _e_, are
the burners of the lamp.
PLATE V. fig. 1. _A Candelabrum_, into which the gas-pipe ascends from
the floor of the apartment, the lateral branches communicating with the
central tube.
Fig. 2. _An Arabesque Chandelier._ The gas enters from the ceiling of
the room into the rope-shaped pipe, _a_, from which it proceeds through
one of the arched ribs, _b_ _b_, into the horizontal hoop, or pipe, _c_.
Fig. 3. _A Roman Chandelier._ The gas enters through the inflexible
hollow chain, _a_, into the central tube, _b_, from whence the burners
are supplied by the lateral branches, _c_ _c_.
Fig. 4. _A Gothic Chandelier._ The gas is transmitted to the burners
through the rope, _a_, which includes a tube, and the communication with
the burners is established through the lateral branches.
Fig. 5. _A Pedestal Figure Lamp._ The gas is here made to pass by means
of a pipe through the body of the figure into the lattice-work
_plateau_, constructed of hollow and perforated brass tubes.
[Illustration]
Fig. 6. _A Pedestal Vase Lamp._ The gas-tube enters through one of the
claw-feet of the altar-shaped pedestal, into the glass vase, _a_, at
the bottom of which it joins the tubes communicating with the metallic
corn-ears, _b_, at the upper extremities of which it forms _jets de
feu_.
Fig. 7. _A Girandole._ The gas enters through the bracket, _a_, and is
conveyed to the burners by the descending tubes, _b_ _b_.
Fig. 8. _A Candelabrum_, having a central pipe, through which the gas is
conducted to the burner at the top.
OTHER PRODUCTS OBTAINABLE FROM COAL: NAMELY, COKE, TAR, ESSENTIAL OIL,
&c.
Having thus far considered the nature of coal-gas as a substitute for
the lights now in use, it will be necessary to attend more particularly
to some other products which are obtained during the production of this
species of light: namely, coke, tar, ammoniacal liquor, &c.
_Coke._--The substance called coke, which constitutes the skeleton of
the coal, or its carbonaceous base, is left behind in the retort, after
all the evaporable products have been expelled from the coal by
heat.--See page 85.
It is sufficiently known, that coke is a more valuable fuel than the
coal from which it is obtained.
Hence, immense quantities are prepared in the large way, but the gazeous
and other substances are lost in the process employed for carbonizing
the coal.[27] In the manufacture of coal-gas, the coke comes from the
retort, enlarged in size, and greatly diminished in weight, when
compared with the original coal. In whatever state the coal may be when
introduced into the retort, the coke is uniformly taken out in large
masses, so that the refuse coal, or dust, and sweepings of the pit,
which are now thrown away, may be employed and converted into an
excellent fuel. Coke is decidedly superior to coal for all domestic, and
more especially for culinary purposes; the heat which it throws out
being more uniform, more intense, and more durable. No flame, indeed,
accompanies it, and it seldom needs the application of the poker,--that
specific for the _ennui_ of Englishmen; but these deficiences are more
than balanced by the valuable property of emitting no sparks, of giving
more heat, and burning free from dust and smoke.
[27] The preparation of coke is as follows:--A quantity of large coal
is placed on the ground in a round heap, of from 12 to 15 feet in
diameter, and about two feet in height; as many as possible of the
large pieces are placed on their ends, to form passages for the air;
above them are thrown the smaller pieces and coal dust, and in the
midst of this circular heap, is left, a vacancy of a foot wide where a
few faggots are deposited to kindle it. Four or five apertures of this
kind are formed round the ring, particularly on the side exposed to
the wind; there is, however, seldom occasion to light it with wood,
for other masses being generally on fire, the workmen most frequently
use a few shovels of coal already burning, which acts more rapidly
than wood, and soon kindles the surrounding pile; as the fire spreads,
the mass increases in bulk, puffs up, becomes spongy and light, cakes
into one body, and at length loses its volatile parts, and emits no
more smoke. It then acquires an uniform red colour, inclining a little
to white, in which state it begins to break into gaps and chinks, and
assumes the appearance of the under part of a mushroom; at this moment
the heap must be quickly covered with ashes, of which there is always
a sufficient provision around the numerous fires, where the coke is
prepared.
That coke must give out more heat during its combustion than coal, will
at once become obvious, when we consider that the quantity of matter
which, in the combustion of coal is changed from a solid to a state of
elastic fluidity, must necessarily carry off a portion of caloric,
which then becomes converted in a latent state without producing heat,
whilst the glow of the coke radiates caloric with an intensity
unimpaired by any demand of this kind.