The invention of Gas Lighting had its origin in the earliest times of
history; not, indeed, as we now see it, burning at the end of a pipe
supplied with gas made artificially, and stored in gas-holders, but
blazing from fissures in the ground, supplied from natural sources in
the bowels of the earth. The Greek fire-altars are supposed to have
been supplied with gas, either issuing from bituminous beds, or made
artificially by the priests, by pouring oil on heated stones placed
in cavities beneath. Fountains of naphtha, and fires issuing from the
earth at Ecbatana, in Media, are mentioned by Plutarch in his life of
Alexander, and many other ancient historians record the knowledge of
similar instances of natural gas lighting.
In later times, the inflammable gas issuing into the galleries of coal
mines, and either exploding when mixed with atmospheric air, or blazing
as it issued from fissures in the coal, afforded instances of the
natural production of gas, the ignition of which too frequently proved
fatal to those in the mines.
A remarkable instance of the issue of inflammable gas into the shaft of
a coal mine at Whitehaven, which produced a blaze about 3 feet diameter
and 6 feet long, is noticed in the "Philosophical Transactions" of
1733. The part whence the gas issued was vaulted off, and a tube was
inserted into the cavity and carried to the top of the pit, where it
escaped in undiminished quantity for years, and lighted the country for
a distance of several miles. Many experiments were made with this large
issue of gas, and it was proposed to conduct it in pipes to Whitehaven,
to light the streets of that town, but the proposition was rejected by
the local authorities.
In China, naturally produced gas is used on a large scale, and was so
long before the knowledge of its application was acquired by Europeans.
Beds of coal, lying at a great depth, are frequently pierced by the
borers for salt water, and from these wells the inflammable gas springs
up. It sometimes appears as a jet of fire from 20 to 30 feet high; and,
in the neighbourhood of Thsee-Lieon-Teing, the salt works were formerly
heated and lighted by means of these fountains of fire. Bamboo pipes
carry the gas from the spring to the places where it is intended to be
consumed. These canes are terminated by tubes of pipe-clay, to prevent
their being burnt, and other bamboo canes conduct the gas intended
for lighting the streets, and into large apartments and kitchens.
Thus Nature presents in these positions a complete establishment of
gas-light works.[9]
Though the production of illuminating gas from natural sources had
been thus long known, the idea of distilling it artificially from
coal, for the purpose of illumination, did not occur until the end of
the last century. Dr. Clayton, indeed, nearly arrived at the practical
application of carburretted hydrogen, in 1737, for he instituted
experiments to prove that coal contains gas, nearly similar to that of
the "fire damp" in coal mines, and that it burns with a bright flame.
At that time, however, the nature of gases was so imperfectly known,
that he was unable to do more than discover that coal possesses the
property of giving out, when heated, gas that will burn with a bright
light.
In the "Philosophical Transactions" of 1739, Dr. Clayton thus
describes the effect of the "spirit of coal," obtained by destructive
distillation in an iron retort. "I kept this spirit," he says, "in
bladders for a considerable time, and endeavoured several ways to
condense it, but in vain; and when I had a mind to divert strangers or
friends, I have frequently taken one of these bladders, and pierced
a hole in it with a pin, and, compressing gently the bladder near
the flame of a candle till it once took fire, it would then continue
flaming till all the spirit was compressed out of the bladder; which
was the more surprising, because no one could discern any difference in
the appearance between these bladders and those which were filled with
common air."
The first known application of coal gas to illumination was made, in
1792, by Mr. William Murdoch, engineer at the Soho manufactory, to
whose great ingenuity the world is also indebted for the invention of
the first plan of a steam locomotive engine.[10] He was at that time
occupied in superintending the fitting up of steam engines for the
Cornish mines, and his attention having been directed to the properties
of gas issuing from coal, he instituted a series of experiments on
carburretted hydrogen, the practical result of which was the lighting
of his house and offices, at Redruth, with coal gas. The mines at which
Mr. Murdoch worked being some miles distant from his house, he was in
the constant practice of filling a bladder with coal gas, in the neck
of which he fixed a metallic tube with a small orifice, through which
the gas issued. The lighted gas issuing through the tube served as a
lantern to light his way; and as he thus proceeded along the road with
the light issuing from the bladder, the country people looked upon him
as a wizard.
The gas was generated by Mr. Murdoch in an iron retort, and collected
in a common gasometer, from which it was conducted in pipes to the
rooms to be lighted. He also, in an early stage of the invention,
contrived a means for making the gas portable, by compressing it into
strong vessels; a plan which, a few years since, was adopted by the
Portable Gas Company in London.
Mr. Murdoch having proved the practicability of illumination by gas
generated from coal, he continued his experiments to facilitate the
manufacture of the gas on a large scale, and for its more perfect
purification. The first public display of its illuminating power was
made at the rejoicings for the peace of Amiens, in 1802, on which
occasion part of the work-shops of Messrs. Boulton and Watt, at Soho,
was brilliantly illuminated with coal gas by Mr. Murdoch. In 1805,
Messrs. Phillips and Lee, of Manchester, had their extensive cotton
mill fitted up with gas apparatus, under the superintendence of Mr.
Murdoch, and the quantity of light given out by the burners in all
parts of the cotton mill was equal to that of 3,000 candles.[11]
Notwithstanding these eminently successful trials of gas lighting,
the prejudice against innovation prevented, for several years, the
extensive adoption of the plan. As every establishment using gas had
to make it, and as the apparatus was costly and imperfectly managed,
the expense in the first instance, the trouble, and the noxious
smell, presented great obstacles to the introduction of that mode of
illumination. The popular notion, also, that streams of flame were
rushing along the pipes produced an impression that gas lighting must
be very dangerous, which it required time to disprove. It was not,
therefore, till several years after the advantages and economy of gas
had been practically established, that a public company was formed
for laying down pipes to light the streets, and to convey the gas into
houses for lighting shops.
The person to whom the world is chiefly indebted for the practical
application of gas lighting is Mr. Winsor, who had been a merchant in
London. Being very sanguine as to the advantages to be derived from
gas lighting, and possessing an ardent temperament which no opposition
could quench, he undertook to introduce it to public notice, and to
form a company for lighting the whole of England with gas. He hired
the old Lyceum Theatre, which he lighted with coal gas, and he there
delivered lectures and exhibited experiments to show the benefits that
would arise from the universal use of gas light, and coke fuel. He
published an extravagant prospectus of a company to be formed, with the
following title:--"A National Light and Heat Company, for providing our
streets and houses with light and heat, on similar principles as they
are now (1816) supplied with water. Demonstrated by the patentee at No.
97, Pall Mall, where it is proved, by positive experiments and decisive
calculation, that the destruction of smoke would open unto the empire
of Great Britain new and unparalleled sources of inexhaustible wealth
at this most portentous crisis of Europe. The serious perusal of this
publication, and an attentive observation of the decisive experiments,
will carry conviction to every mind."
In this prospectus Mr. Winsor attempted to make it appear that by
adopting his plan there would be "a grand balance of profit for the
whole realm of £115,000,000," and each shareholder of the company was
promised, "at the lowest calculation, £570 for every £5 deposit." He
entertained the notion of making the use of gas and coke compulsory, by
levying a tax on all who obstinately refused to adopt what would be so
much to their own advantage. This tax, he said, "cannot be oppressive
in the least, because it falls on the obstinate only, who shall resist
the use of a far superior, cheaper, and safer fuel." Not content with
the language of prose, Mr. Winsor vented his thoughts and feelings in
numerous poetical effusions. The flights of his Muse, however, were not
into the regions of sublimity, as may be perceived by the following
specimen:--
"Must Britons be condemned for ever to wallow
In filthy soot, noxious smoke, train oil, and tallow,
And their poisonous fumes for ever to swallow?
For with sparky soot, snuffs and vapours, men have constant
strife,--
Those who are not burned to death are smothered during life."
Mr. Winsor's absurd statements--in the truth of which he potently
believed--and the wild, random manner of making them known, excited
much ridicule and opposition. Among his opponents was Mr. Nicholson,
the editor of the _Chemical Review_, who not only challenged Mr.
Winsor's estimates, but the validity of his patent, on the ground
that Mr. Murdoch was the original inventor. Mr. Winsor's plans and
calculations were burlesqued in a cleverly written "Heroic Poem,"
published in a quarto volume, which, whilst professing to extol the
virtues of gas and coke, quizzed its hero most unmercifully. The poem
concluded with this address:--
"And when, ah, Winsor!--distant be the day!--
Life's flame no longer shall ignite thy clay,
Thy phosphur nature, active still, and bright,
Above us shall diffuse _post obit_ light.
Perhaps, translated to another sphere,
Thy spirit--like thy light, refined and clear--
Ballooned with purest hydrogen, shall rise,
And add a PATENT PLANET to the skies.
Then some sage Sidrophel, with Herschel eye,
The bright _Winsorium Sidus_ shall descry;
The _Vox Stellarum_ shall record thy name,
And thine outlive another Winsor's fame."
"Though we may smile at Mr. Winsor's extravagant plans and
calculations," observes the _Journal of Gas Lighting_, "we cannot but
admire the enthusiasm with which he pursued his object, and ultimately
succeeded in establishing the first gas company. The lighting of Pall
Mall with gas, in the spring of 1807, gave increased stimulus to the
project, and application was made to Parliament to carry it into
effect. The bill was opposed by Mr. Murdoch and thrown out; but in
the following year (1810) the application was successfully renewed.
The scheme, however, as sanctioned by Parliament, was sadly shorn
of its magnificent proportions; and, instead of a 'Grand National
Light and Heat Company, for Lighting and Heating the Whole Kingdom,'
its operations were limited to London, Westminster, and Southwark;
nor were any special taxes imposed on those who should obstinately
refuse to use the light and burn the coke. The Chartered Gas Company,
established by Mr. Winsor's persevering efforts, has served as the
guiding star to all other gas companies in the world."
The illuminating property of coal gas depends on the quantity of carbon
it contains. Pure hydrogen gas burns with a pale blue flame that gives
scarcely any light, though it possesses intense heating power. If,
however, minute particles of a solid body--powdered charcoal, for
instance--be thrown into the flame, they become white-hot, and the
incandescence of those solid particles produces a brilliant light. The
same effect is caused by the combustion of the carburretted hydrogen
gas, and in a more perfect manner. That gas contains a large portion
of carbon in a state of vapour, and when a light is applied to a jet
of the gas the hydrogen immediately inflames, the carbon is deposited
in the flame, and the minute particles into which it is disseminated
become highly heated and ignite.
There are two distinct states of carbonization in illuminating gas.
The commoner kind--the ordinary coal gas--consists of two measures
of hydrogen mixed with one measure of carbon vapour. The specific
gravity of such gas is about one-half that of atmospheric air, and
it is eight times heavier than pure hydrogen.[12] The best kind of
gas for illumination is obtained from the distillation of oil. It is
called olefiant gas, and contains equal measures of hydrogen gas and
carbon vapour; its specific gravity is 0.985, being about fifteen times
heavier than pure hydrogen.
The _rationale_ of the process of making coal gas consists in expelling
the volatile matters from the coal by heat, in closed vessels or
retorts, and then separating the gas and purifying it on its passage
from the retort to the gas-holder, where it is stored for use.
The retorts are usually made of cast iron, and are about 7 feet long,
14 inches in depth, and the same in width; the shape being that of
an arch. The retorts will hold two hundredweight of coal each, but
they are never filled, because during the process of distillation the
carbonaceous part of the coal expands, and occupies more space than
the original quantity, the proportion of expansion being as one and a
quarter to one. There is a large aperture for the admission of coal
and the extraction of coke, which aperture is covered with a lid, and
screwed to make it air-tight. A tube is inserted into the mouth of the
retort, to carry off the products of the distillation. That tube rises
about twelve feet, and then dips into a large horizontal pipe, one foot
in diameter, called the hydraulic main, in which are collected the
tar and ammoniacal liquor that distil from the coal. Ten or fourteen
retorts are usually set back to back in brickwork, to be heated by one
fire; but the plan has been recently introduced of employing long clay
retorts, which are charged at both ends. These are found to possess
considerable advantage over iron, not only from their lower price, but
from the facility with which the carbonaceous deposit is removed, and
the full charges worked off. Coke is generally burned in the furnaces,
and the heat is continually maintained so as to keep the retorts
red-hot.
As atmospheric air cannot gain access to the coal in the retorts, the
gases expelled do not inflame, nor can the parts that are not volatile
be consumed without a supply of air. It is entirely a process of
distillation, in which all the products can be collected. The volatile
parts are carried off by the pipe, and the solid carbonaceous matter,
or coke, is left in the retort.
The first effect of heat on coal, after it is put into the retort,
is to expel the moisture, which, in combination with the air, issues
in the form of steam. Tar then distils, with some portions of gas,
consisting of hydrogen and ammonia. When the retort has attained a
bright cherry-red heat, the disengagement of the carburretted hydrogen
is most active; and it is found that the more quickly the coal is
heated, the greater is the quantity of illuminating gas generated.
The production of coal gas, and the development of its properties at
different stages of distillation, may be readily shown by means of
a common tobacco pipe. Fill the bowl of the pipe with small pieces
of coal, cover it over with a lump of clay, and then put it into a
hot fire, with the stalk of the pipe projecting through the bars.
Presently steam will be seen to issue from the pipe, and afterwards
smoke, and, if a light be applied, a jet of flame will issue forth, the
brilliancy of which will increase as the bowl of the pipe becomes more
heated, until the best part of the gas has been distilled from the coal.
The gas is mingled with various volatile products as it issues from
the retort, and requires to be purified before it is fitted for
illumination. The most abundant matter that passes over with it is tar.
The vapour of that substance, however, condenses when cooled, and it
may thus be separated from the gas very effectually. For that purpose
the gas, after having deposited a large portion of the tar in the
hydraulic main, is made to traverse through a number of vertical pipes,
and in passing through them a further quantity of tar, accompanied by
ammoniacal liquor, is deposited, and collected in a reservoir at the
bottom. The next process is the purification of the gas from carbonic
acid and sulphuretted hydrogen. This is commonly done by passing it
through water and lime; the combination of the carbonic acid with the
lime being facilitated by agitation. The method of purifying by lime
was introduced by Mr. Clegg; and by a later process, oxide of iron is
used to absorb the sulphuretted hydrogen. The gas, when purified, is
conveyed to the gas-holder, whence it is forced by pressure into the
mains and pipes.
An apparatus for generating coal gas on a small scale for private
establishments, remote from sources of ordinary supply, is represented
in the accompanying woodcut. The retort, A, is fitted in a small
furnace. The coal is put in at F, and the products of distillation pass
through the bent pipe, E. The more liquid portions of the tar pass at
once through the tube, B, into the receiver, G; and as the gas passes
along the bent tube, C, it becomes cooled, and a further deposit of tar
and ammoniacal liquor is made. The gas is then conveyed along another
tube into the purifier, H, filled with lime and water, and it thence
passes into the gas-holder. Tubes are inserted into the latter for
conveying the gas to the burners.
[Illustration]
The quantity and the quality of the gas yielded by coal differ
materially according to the kind employed. One ton of good Newcastle
coal will yield 9,500 cubic feet of gas, which, when burnt in the
best manner, gives a light equal to that of 422 lbs. of spermaceti
candles. One ton of Wigan cannel coal yields 10,000 cubic feet, and
gives a light equal to 747 lbs. of spermaceti candles.[13] The price,
in London, of good gas from Newcastle coal, is 4s. 6d. per thousand
cubic feet, which gives a light equal to 74½ lbs. of spermaceti, and
equal to 89 lbs. of mould candles; therefore, when the latter are 8d.
a pound, the burning of gas is twelve times more economical than the
burning of candles. In Liverpool, gas from cannel coal is supplied at
the low price of 3s. 9d. per thousand feet; and that gas gives at least
one-third more light than the ordinary London gas.
The cleanliness of gas, as compared with candles or oil, is a
further recommendation; and for the purpose of lighting streets,
shops, factories, public buildings, and halls, it presents important
advantages; but it is not well adapted for small sitting rooms, because
the heat of the flame makes it unpleasant and injurious to the eyes
when near, and, unless very pure, it deteriorates the air of closed
apartments. In many parts of the country, however, where coals are
cheap, and the price of gas is consequently less than in London, it is
introduced into every room of nearly all private houses.
The best kind of gas made from mineral substances is produced by the
distillation of a bituminous shale, called Boghead coal, which was
discovered a few years since in Scotland. One ton of this material
yields 15,000 cubic feet of gas, which is equal in illuminating power
to 1,930 lbs. of sperm candles. Boghead coal is now commonly used
for mixing its gas with that of inferior quality, to bring up the
illuminating power to the required standard.
Olefiant gas, made from oil, burns with a brighter and purer light
than common coal gas, but it is more costly. It is made nearly in the
same manner, by distillation in retorts; the principal difference
consisting in the degree and regulation of the temperature. A dull red
heat is the best, and in order to keep the oil exposed to the action
of an invariable heat, it is admitted gradually into the retorts, into
which pieces of brick or coke are inserted to increase the heating
surface. One pound of common oil yields about 15 feet of olefiant gas.
The same kind of gas may also be obtained in smaller quantities by the
distillation of tar, rosin, or pitch. Twelve cubic feet of gas may be
obtained from one pound of tar, and ten from the same weight of rosin.
The brilliancy of gas-light depends, in some measure, on the kind of
burner employed. To obtain a steady light, an argand burner is usually
adopted; the gas being allowed to escape through a number of minute
holes pierced in a hollow ring of metal, which admits a current of
air through the middle. To increase the supply of air, the burner is
covered with a glass chimney, which, if not too long, adds to the
brilliancy of the flame; but a very long chimney produces so strong a
current of air, as to cool the flame, and diminish the light. A plan
is sometimes adopted of placing a small metal disc a short distance
above the jets, so as to spread the flame. By this means the brightness
is increased, by exposing the flame more directly to the current of
air; and the metal disc, by becoming heated, also tends to aid the
combustion of the carbon.
One of the problems to be solved on the original formation of gas works
was the size of pipes, and the amount of pressure required to force the
gas to the various burners. It was at first supposed that the friction
against the pipes would oppose so much resistance to the passage of the
gas, that it could not be transmitted to great distances. It was found,
however, that the perpendicular pressure of a few inches of water was
quite sufficient to force the gas through the mains and small pipes of
an extensive range of streets. A bold attempt was made at Birmingham,
in 1826, to bring gas from the collieries, at a distance of ten miles
from the town. The plan was laughed at by many as impracticable, but it
was attended with complete success. The gas being made near the mouth
of the coal-pit, the cost of conveyance was saved by the additional
outlay in the first instance. It must be observed, however, that it
is extremely difficult in practice to avoid the escape of gas at the
junctions of the pipes; and by increasing the length of the gas mains,
the greater will be the leakage. The loss from this cause, in some gas
works, exceeds 20 per cent. of the gas manufactured.
The volume of gas discharged from a pipe is directly proportional to
the square of its diameter, and inversely as the square of its length.
Thus, if a pipe required to discharge 250 cubic feet of gas in an hour,
at a distance of 200 feet, must have an internal diameter of 1 inch;
to discharge 2,000 feet in an hour, at a distance of 1,000 feet, would
require a diameter of 4·47 inches. The same quantity discharged at
double the distance would require a pipe 5·32 inches in diameter; at a
distance of 4,000 feet the diameter must be increased to 6·13 inches;
and at a distance of 6,000 feet the diameter should be 7 inches.
On the first introduction of gas-light, the companies who supplied
it charged a fixed sum for each burner of a given size. This mode of
charging was, however, very unsatisfactory, for the size of the burner
is a very uncertain indication of the quantity of gas consumed. Persons
using gas desired to pay for the quantity they actually burned; and
to enable them to do this, a special contrivance was invented by Mr.
Clegg, the engineer of the Chartered Gas Company, called a gas-meter.
That instrument measures, with sufficient accuracy for practical
purposes, the volume of gas that passes through it to the burners, and
thus each consumer of gas now pays only for the number of cubic feet
consumed.
The accompanying diagrams represent sections of a gas meter, as seen
in front and edgewise. The outer case of the instrument, which is a
flat cylinder made of sheet iron, is indicated by the letters _c_, _c_.
Inside it there revolves another cylinder, made also of thin sheet
iron, and divided into four compartments, marked _d_, _d_, _d_, _d_.
This interior cylinder readily revolves on an axis, _g_, _g_, shown in
the section of the instrument as seen edgewise. The gas enters from
the street pipe through the opening, _a_, and it is forced out to the
burners through the pipe, _b_, the latter being seen in the narrow
section only. In that diagram, also, there is shown a cog-wheel, _h_,
fixed on to the axis, and a small outer case, in which that wheel
rotates. Water is poured into that external case until the gas-meter is
rather more than half filled, the level of the water being shown at _i_.
[Illustration]
The action of the instrument will be readily understood by examining
the two sections. The gas, on entering the tube, _a_, presses against
the upper surface of the compartment that happens to be then above it,
and tends to turn the inner cylinder round. This pressure forces the
gas through the opening, _b_, to the burner; and as the compartment
then in communication with that opening is emptied of the gas it
contains, in the direction of the arrow, it is gradually forced under
the level of the water, and the other compartment, which has in the
meantime been filling with gas, continues the supply. Thus, supposing
each division of the inner revolving cylinder to hold 108 cubic
inches, a complete revolution would indicate that the fourth part of a
cubic foot had passed through the pipe, _b_, to the burners. Several
cog-wheels, arranged like clock-work mechanism, are connected with
the wheel, _g_, and by this means the number of cubic feet of gas
consumed is indicated by hands fixed to the wheels, and pointing to the
corresponding figures on a series of dials.
Some inconvenience and irregularity having been experienced in the
use of the wet meter, the correctness of which, it is evident, may be
affected by variations in the height of the water level, dry meters
have been constructed for measuring gas, by causing it to pass through
a small expanding chamber, similar in principle to a pair of bellows.
The objection to these instruments is that the leather, or other
flexible substance that forms the sides of the expanding chambers,
becomes rigid by use, and the valves are liable to get out of order;
but in the last improvement of the instrument, by Mr. Croll, these
objections are stated to be effectually removed.
Numerous attempts have been made to produce illuminating gas from other
substances than coal, but without advantage. The plan that promised the
most success was the production of hydrogen gas by the decomposition
of water, which was passed over heated coke in retorts, and by that
means the oxygen of the water, combined with the incandescent coke and
the hydrogen, was set free. The gas thus collected possessed little
illuminating power, but it was afterwards mixed with the rich gas from
cannel coal, and raised to the requisite illuminating standard. It was
found, however, in practice, that the compound gas thus formed was more
costly than ordinary coal gas, and the plan has been discontinued.
Another method of giving illuminating power to water gas was to
surround the flame with platinum gauze, which was rendered incandescent
by the heat, and became highly luminous. But it required twice the
quantity of gas burned in this manner to produce a light equal to that
of carburretted hydrogen, and the combustion of so much hydrogen gas
produced an amount of vapour and heat that were very unpleasant. That
mode of gas illumination, called the "Gillard light," from the name
of the inventor, was also found more costly than the ordinary mode of
lighting with coal gas, which has now no rival to compete with it in
economical illumination.
No Act of Parliament is now required, as originally proposed by
Mr. Winsor, to enforce the burning of coal gas. Its advantages, in
point of economy, cleanliness, and even of safety, are sufficiently
understood to spread the use of coal gas to every part of the kingdom.
In the metropolis alone there are twelve gas companies, who receive
for the sale of gas an average of £100,000 per annum each, thus making
the sum paid for gas lighting in London £1,200,000, and it has been
estimated as high as £2,000,000. Taking the average price to be 4s.
6d. per thousand cubic feet, the quantity of gas consumed amounts
to 5,300,000,000 cubic feet; and if we add to that quantity 20 per
cent. for leakage through the mains and pipes, the quantity of gas
manufactured in the metropolitian gas works is upwards of 6,000,000,000
cubic feet in a year. It may, perhaps, give a clearer notion of this
immense quantity to say, that a gas-holder, capable of containing it,
would require to be one mile in diameter, and the height of St. Paul's
Cathedral. The light produced by burning such a volume of gas would
be equal to that of 150,000 tons of mould candles, which would cost
£13,000,000. The quantity of coals requisite for the production of the
gas manufactured annually in London is upwards of 600,000 tons.