[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.
[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 portionof caloric, which then becomes converted in a latent state without producing heat, whilst the glow of the coke radiates caloric with an intensity unimpaired by any demand of this kind.
It is thus that coke, though somewhat more difficult of ignition than common coal, always gives out a more steady, a more lasting, and a more intense heat.
The only inconveniences that attend the use of coke is, that, as it consumes, it leaves much more ashes than common coal, charcoal, or wood; and these much heavier too, which are, therefore, liable to collect in such quantity as to obstruct the free passage of air through the fire; and further, that when the heat isvery intense, these ashes are disposed to melt or vitrify into a tenacious drossy substance, which clogs the grate, the sides of the furnace and the vessels. This last inconvenience is only troublesome, however, when the heat required is very great. In ordinary heats, such as are produced by kitchen or parlour grates, the ashes do not melt, and though they are more copious and heavy than those of charcoal or wood, they do not choke upthe fire, unless the bars of the grate be too close together.
The relative effects of heat produced by coke and coal are as follows:—
Six hundred pounds of pit-coal are capable of evaporating 10 cubic feet of water in 20 hours, and 430lb. of coke are capable of evaporating 17 cubic feet of water in 12 hours and a half.[28]
[28]In order to learn the relative effect of different kinds of fuel, with regard to their capability of producing heat, chemistry teaches that equal quantities of fuel alike expended, will raise the temperature of a given quantity of water through the same number of degrees; whence, by knowing the original quantity and temperature of water, together with the quantity of fuel expended to raise the water to the boiling point, the result sought may be expressed by stating the quantity of water at 30 degrees, which would have been raised 180 degrees by one pound of the fuel employed; or in the form of a rule,Multiply the quantity of water by the number expressing the degrees actually raised; multiply the number of pounds of fuel expended by 180 degrees. Divide the first product by the latter, and the quotient will express the water which would have been raised 180 degrees by one pound of the fuel. Or equal quantities of water may be compleatly evaporated under equal surfaces and circumstances, with the different kinds of fuel, the nature of which is to be examined; the quantities of fuel expended for that purpose give the relative effect of the different kinds of fuel, with regard to their power of producing heat.
[28]In order to learn the relative effect of different kinds of fuel, with regard to their capability of producing heat, chemistry teaches that equal quantities of fuel alike expended, will raise the temperature of a given quantity of water through the same number of degrees; whence, by knowing the original quantity and temperature of water, together with the quantity of fuel expended to raise the water to the boiling point, the result sought may be expressed by stating the quantity of water at 30 degrees, which would have been raised 180 degrees by one pound of the fuel employed; or in the form of a rule,
Multiply the quantity of water by the number expressing the degrees actually raised; multiply the number of pounds of fuel expended by 180 degrees. Divide the first product by the latter, and the quotient will express the water which would have been raised 180 degrees by one pound of the fuel. Or equal quantities of water may be compleatly evaporated under equal surfaces and circumstances, with the different kinds of fuel, the nature of which is to be examined; the quantities of fuel expended for that purpose give the relative effect of the different kinds of fuel, with regard to their power of producing heat.
The Earl of Dundonald has shown that, in the application for burning lime, a quantity of coke uniformly burns a given portion of lime-stone in one-third part of the time that the quantity of coal from which the coke had been made could do.
This effect is to be accounted for from having previously freed the coal, or rather its coke, from the moisture and the tar, which it sends out during combustion, and which condenses on the middle and upper strata of stratified limestone and coal in the lime kiln, and impedes the whole mass of materials from coming into a rapid and compleat ignition; because the greater the quantity of materials, and the sooner the whole is ignited, the better and more economically the lime is burned, both as to coals and time; the saving of which last is a material object, especially at lime-kilns where there is in the summer time a great demand for lime, the coke occasioning the kilns to hold athird more limeat thesame time.
In the art of making bricks, in the smelting of metallic ores, and the drying of malt, the advantages of coke over coal, are sufficiently known.
The following account given by Mr. Davis,[29]shows that the advantages that may be derived in the processes of burning lime, plaster of paris, and bricks, by means of coke, are greater than at first sight might be imagined.
[29]Philosophical Magazine, Vol. 33, p. 435.
[29]Philosophical Magazine, Vol. 33, p. 435.
“The coke obtained in the gas process is so valuable, that it appears inexplicable that men should not avail themselves of this mode of procuring light, to the almost total exclusion of all other methods now in use. As a landholder, placed among an industrious but wholly illiterate society of men, I have had the more opportunity of trying this species of fuel or coke, which I could not otherwise procure in this sequestered spot, at a tolerably cheap rate, for purposes to which it has not, as far as I know, been hitherto employed. I must tell you that I am my own lime-burner, plaster of paris baker, and brick-maker; and that in these processes of rural economy I have derived the greatest benefits from this species of fuel, which I now prepare at a cheap rate, although I waste almost the whole of the light of the coal gas intentionally. The coal which I employed formerly for the burningof limestone into lime, is a very inferior kind of small coal, called here Welsh culm. The kiln for burning the limestone into lime is a cup-shaped concavity, surrounded with solid brick-work, open at the top, and terminating below by an iron grate. It has a stone door that may be opened and closed for charging and emptying the furnace when required. This furnace I formerly charged with alternate strata or layers of small coal and limestone, the latter being broken previously into pieces not larger than a man’s fist, until the kiln was completely filled. The stone is thus slowly decomposed; the upper part of the charge descends, and when it has arrived at the bottom of the furnace new strata are super-imposed, so as to keep the furnace continually full during a period of 50 hours. The quantity of lime I procured with small coal formerly amounted to 85 bushels. The strata of coal necessary for the production of this quantity of lime require to be four inches thick, and the time necessary for calcination was, as stated already, 50 hours.
“On applying coke instead of coal, the produce of lime may be increased to nearly 30per cent. from the same furnace, and the time required to effect the calcination of this quantity of lime-stone is reduced to 39 hours: it also requiresless attendanceandless labour, and the whole saving, thus accomplished, amounts to more than 50per cent. on the lime-kiln.
“I have lately also employed coke for the burning of bricks. My bricks are burnt in clamps, made of bricks themselves. The place for the fuel, or fire-place, is perpendicular, about three feet high. The flues are formed by gathering or arching the bricks over, so as to leave a space between each of a brick’s breadth; and as the whole of the coal, if this fuel be employed, must, on account of the construction of the pile, be put in at once, the charge of the bricks is not, and never can be, burnt properly throughout; and the interference of the legislature, with regard to the measurement of the clamp, is a sufficient inducement for the manufacturer to allow no more space for coal than he can possibly spare.
“If coke be applied instead of coal, the arches, or empty spaces in the clamp or pile,as well as the strata of the fuel, may be considerably smaller: the heat produced in this case is more uniform and more intense, and a saving of 30 per cent. at least is gained.
“In the baking my own plaster-stone I also employ coke. The calcination of the stone for manure I perform in a common reverberatory furnace, and the men who conduct the process (who are otherwise averse to every thing new) are much pleased with the steadiness of the fire, and little attendance which the process requires, when coke is used instead of coal.
“These are the few facts I wish to state, with regard to the useful application of this species of fuel, which, no doubt, hereafter will become an object of economy of incalculable advantage to individuals, if its nature be better understood than it is at present.”
The quantity of coke obtainable from a given quantity of coal varies according to the nature of the coal employed. One chaldron of Newcastle coal produced, upon an average, in the gas-light manufacture, from one chaldron and a quarter to one chaldron and a half of well formed coke. If the carbonization of the coal has been carried to its utmost point,the coke produced, has a brilliant silvery lustre. Such coke is excellent for metallurgical operations, because it stands the powerful blast of the bellows, but for culinary and other purposes of domestic economy, the carbonization should not be carried so far, because, the coke then produced, kindles more readily and makes a more cheerful fire.
Coal-tar,Oil, andPitch.—Another, valuable product obtainable from pit-coal, is coal-tar.[30]This substance is deposited, in the purification of the coal-gas, in a separate vessel destined to receive it.
[30]In the year 1665, Becher, a German chemist, brought to England his discovery for extracting tar from coal, this distillation he performed in close vessels. It is not mentioned in the records of the time, whether Becher obtained, or rather collected, any other articles than the tar.
[30]In the year 1665, Becher, a German chemist, brought to England his discovery for extracting tar from coal, this distillation he performed in close vessels. It is not mentioned in the records of the time, whether Becher obtained, or rather collected, any other articles than the tar.
The coal-tar is so called from its resembling common tar in its appearance, and most of its qualities.
Several works have been, at different times, erected both in England and on the continent, to procure from coal a substitute for tar; but they turned out unprofitable speculations. In 1781, the Earl of Dundonald invented a mode of distilling coal in the large way, which enabledhim not only to form coke, but, at the same time, to save and collect the tar. Even this process however, for which a patent was taken out, has gained very little ground. Its object was still too limited; for though some of the ingredients of coal were procured, they were procured at an expense that nearly balanced the profits; and no attention whatever was paid to the coal gas, which constitutes the most important part of coal.
Coal-tar may be used with advantage for painting and securing wood that is exposed to the action of air or water. The wood being warmed, the tar is applied cold, and penetrating into the pores, gives the timber an uncommon degree of hardness and durability.
One chaldron of Newcastle coal produces in the gas-light manufacture from 150 to 180lb of tar, according to the circumstances under which it is produced. Seepage 94.
The tar obtained from Newcastle coal-tar is specifically heavier than that produced from cannel-coal; hence it sinks in water, whereas the latter swims on the surface of that fluid.
To render the tar fit for use, it requires to be evaporated to give it a sufficient consistence.If this process be performed in close vessels, a portion of an essential oil is obtained, which is known to colourmen by the name of oil of tar. To obtain this oil, a common still is filled with the coal-tar, and, being properly luted, the fire is kindled and kept up very moderate, for the tar is very apt to boil up in the early part of the process. The first product that distils over is principally a brown ammoniacal fluid, mixed however with a good deal of oil. As the process advances, and the heat is increased, the quantity of ammoniacal liquor lessens, and that of oil increases, and towards the end of the distillation the product is chiefly oil.
The oil and ammoniacal water which distil over do not mix, so that they may be easily separated by decantation. The oil is a yellowish inferior kind of oil of turpentine, which is very useful in painting ships, for making varnishes, and other coarse out-door work.
Two hundred pounds of tar produce, upon an average, fifty-three pounds of essential oil.
If the coal-tar is wanted to be converted into pitch, without obtaining the oil which it is capable of furnishing, the evaporation of itmay be performed in a common boiler; but as it is extremely liable to boil over, the greatest precaution is necessary in conducting the evaporation. A boiler constructed on the following plan is very convenient for the conversion of coal-tar into pitch. The contrivance consists in adding a spout, or rim, to the common boiler, into which the tar spreads itself as it rises, and by this means becomes cooled, and the boiling over is checked.
Kettle for boiling Tar.
Kettle for boiling Tar.
1000lb. of coal-tar produce, upon an average, from 460 to 480lb. of pitch. A subsequent fusion, with a gentle heat, converts the coal-pitch into a substance possessing all the characters ofasphaltum.
Ammoniacal Fluid.—The properties of the ammoniacal liquor, which accompanies the tar,and which is deposited in the tar-cistern, has not yet been fully investigated. It is employed already in the manufacture of muriate of ammonia (sal ammoniac). One chaldron of coal affords from 220 to 240lb. of this ammoniacal fluid, which is composed chiefly of sulphate, and carbonate of ammonia.—Such are the products obtainable from coal.
However certain the practicability of extending the new lights to the dwelling houses of every town and village is, it cannot be expected that such an event should take place speedily and generally. To eradicate prejudice, and to alter established habits, is a work which nothing but time can effect; because prejudice is the effect of habit, and can seldom be eradicated from the minds of such individuals as consider the ready occurrence of a proposition as a test of its truth. To establish a new philosophical theory has, in every instance, required time sufficient to educate an entire generation of men. The rejection of the Aristotelian philosophy—the adoption of experimental research—the substitution of the doctrine of gravitation instead of that of vortices, and the rejection of phlogiston by modern chemists, aresufficiently illustrative of this assertion. New arts, and new practices, are still more difficult to be introduced. The new art of bleaching need merely be mentioned to prove this assertion. The new grammar—the new rudiments of science—the new stile—or the new instrument, however superior to the old in simplicity, facility, and truth, must be less valuable to the ordinary teacher or artisan, whose memory is familiarized with the precepts of the latter, and whose only ambition is to earn his subsistence with the least possible exertion.
The slowness with which improvements of every kind, make their way into common use, and especially such discoveries as are most calculated to be of an extended or general utility is very remarkable, and forms a striking contrast to the extreme avidity with which those unmeaning changes are adopted, which folly and caprice are continually sending forth into the world under the auspices offashion.
On the first view of the subject it appears very extraordinary, that any person should neglect, or refuse to avail himself of a proposed invention, or improvement, which is evidently calculated to economise his labour,and to encrease his comforts; but when we reflect on the power of habit, and consider how difficult it is for a person even to perceive the disadvantages or imperfections of former modes to which he has been accustomed from his early youth, our surprize will be diminished, or vanish altogether.
Many other circumstances, besides prejudice, are unfavourable to the introduction of new and useful discoveries. Among these jealousy, malice, envy, and revenge, have too often their share in obstructing the progress of real improvement, and in preventing the adoption of plans evidently calculated to promote the public good.
A plan like the present, which proposes not only to trench upon domestic habits, but to give an entire new direction to a portion of the skill and capital of the country, must necessarily encounter the most strenuous opposition. It is thus that some individuals have mustered all their strength against the introduction of this new art. An endeavour has been made to move the public opinion by dismal forebodings of the Greenland trade, and the subsequent loss of a nursery of British seamen. This objectionis nothing more than the common clamour that is always set up against every new means of abridging labour, to which had the public listened, an interdict would have been laid upon the spinning and threshing machines, the steam engine, and a thousand other improvements in machinery.
Indeed such clamour scarcely ever fails to be made when the extension of machinery and the abridgement of labour or the application of inanimate powers are considered. On such occasions, it is stated by certain humane but mistaken objectors, that the scheme of mechanical and chemical improvement is pointed against the human species—that it tends to drive them out of the system of beneficial employment—that the introduction of machinery is injurious to the labouring class of society, by abridging their work. Two creatures offer themselves for employment and support—a man and a horse. I must invariably prefer the latter, and leave the former to starve. Two other beings—a horse and a steam-engine, are candidates for my favour. My preference to the latter tends to exterminate the species of the former. In both cases it is stated, that the number of intelligentcreatures capable of the enjoyment of happiness must be diminished for want of support; and that, on the whole, the sum of the proposed improvement is not only a less proportion of good to society, but a positive accession of misery to the unemployed poor.
On this wide and extended argument, which can in fact be maintained against all improvements whatever in no other way than by insisting that the savage state of man, with all its wants, its ignorance, its ferocity, and its privations, is preferable to the social intercourse of effort and division of labour we are habituated to prefer, it may be sufficient to observe that it includes matter not only for reasoning and induction, but also for experiment. By reference to the matter of fact, though it must be allowed that new improvements, which change the habits of the poor, must at first expose them to a temporary inconvenience and distress, against which, in fairness, it is the duty of society to defend them; yet the invariable result of such improvements is always to better the condition of mankind. A temporary inconvenience to individuals must often be incurred for the sake of general national benefit.
It is to manufactories carried on by machinery and to the abridgment of labour, that this country is indebted for her riches, her independence and pre-eminent station among the nations of the world.
But let us return to the subject.—The progress of the new mode of lighting with coal-gas can never wholly supersede the use of candles and moveable lights. The objection with regard to the Greenland trade is equally futile. This traffic, might with more propriety be called a drain, than a nursery, of the naval force. The nature of the Greenland service requires that the crew should consist chiefly of able-bodied sailors; and being protected men, not subject to the impress law, they are thus rendered useless for national defence. The nursery of British seamen is the coasting trade; and if the gas-light illumination be put in practice to a large extent, it will increase that trade as much as it will diminish the Greenland fishery.
Even on the extreme supposition that it would annihilate the Greenland fisheries altogether, we should have no reason to regret the event. The soundest principles of politicaleconomy must condemn the practice of fitting out vessels to navigate the polar seas for oil, if we can extract a superior material for procuring light at a cheaper rate from the produce of our own soil.
Indeed the fisheries will find ample encouragement, and the consequence of lighting our streets with gas can prove injurious only to our continental friends, one of whose staple commodities, tallow, we shall then have less occasion to purchase.
There will be less waste indeed, but a greater consumption of coal. The lower classes of the community are at present very scantily supplied with firing; and nothing but a reduction of price is necessary to increase to a very large amount the whole average quantity of fuel consumed in the country. The lightness of the coke produced in the gas-light manufacture diminishing the expence of land carriage, will facilitate its general diffusion—the comforts of the poor will be materially augmented, and a number of useful operations in agriculture and the arts be carried on, which are now checked and impeded by the price of fuel.
If any additional want were wanted for thecoke it will readily be found in the continental market; coke being much better suited than coal to the habits of most European nations.
The gas-light illumination cannot tend to diminish the coal-trade; on the contrary it will prove beneficial to it; it will contribute to lower the price of the superior kinds of coal, and keep a level which cannot be shaken under any circumstances; it will contribute to prevent combinations which do certainly operate to the prejudice of the public, and do sometimes put this great town at the mercy of particular proprietors in the north, who deal out coal in the way they please. The competition thus produced, it is impossible not to consider as an advantage, which would prevent in future such combinations, and put those in London out of the reach of them.
It is worthy observation, that the annual importation of coal into this Metropolis, is above one million and eighty-eight thousand chaldrons.[31]
[31]To give an idea how long there is a probability of Great Britain being applied with coal from the rivers Tyne and Wear only, it must be observed,1st. That the Seams of coal which are now worked at Newcastle and Sunderland, are equal to a seam or bed of 15 miles by 20 miles.2dly. That this seam, on an average, is at least four feet and a half thick.3dly, That 1-6th part of the above extent is sufficient for pillars to support the roofs of the mines, &c.And,4thly, It appears, by experiments, that a cubic yard of coal weighs 1 ton, or 20 cwt.London ChaldronsThe total consumption of coal from the rivers Tyne and Wear known from the register to be2,300,000The number of tons in the above quantity taking the London chaldron at 27 cwt. is3,100,000Now a ton weight of coal is estimated to occupy in the earth the space of one cubic yard.The number of cubic yards in the square mile is3,097,600The beds or seams of coal are, on an average, 4 feet and a half in thickness, which increases the above number of cubic yards in the square mile by half the number of square yards to1,548,800And hence the square mile of the beds or seams of coal we are describing contains, of cubic yards and tons of coal4,645,000A deduction of 1-6th for pillars to support the mine, &c.800,000The number of tons per square mile5,445,000We have already mentioned the length and breadth of the seams of coal to be equal to 20 miles by 15, making an area of 300 square miles, and consequently a source of consumption for 375 years.
[31]To give an idea how long there is a probability of Great Britain being applied with coal from the rivers Tyne and Wear only, it must be observed,
1st. That the Seams of coal which are now worked at Newcastle and Sunderland, are equal to a seam or bed of 15 miles by 20 miles.
2dly. That this seam, on an average, is at least four feet and a half thick.
3dly, That 1-6th part of the above extent is sufficient for pillars to support the roofs of the mines, &c.
And,4thly, It appears, by experiments, that a cubic yard of coal weighs 1 ton, or 20 cwt.
We have already mentioned the length and breadth of the seams of coal to be equal to 20 miles by 15, making an area of 300 square miles, and consequently a source of consumption for 375 years.
It may be objected to the universality of our conclusion, that the price of coals, differing very much in different places, will occasion a variation in the expence of the new mode ofillumination. But there are two reasons why this should have less place, because we find, in Mr. Murdoch’s statement,page 69, that of 600l. the estimated yearly expence of lighting the cotton mill, 550l. consist of interest of capital, and tear and wear of apparatus, leaving the cost of coal only 50l. a sum so trifling, when we reflect that it replaces 2000l. worth of candles, that the price of coal, even where it is highest, can but slightly affect the general profits.[32]
[32]See, also, Mr. Ackermann’s statement,page 71.
[32]See, also, Mr. Ackermann’s statement,page 71.
2dly, The coal, by yielding the gas and other products,—namely, tar, pitch, ammoniacal liquor, &c. of which we have treated already, is converted into a substance, increased in bulk, and in the power of producing heat, namely, coke; and as a manufactory generally requires heating as well as lighting, there will be a gain both ways. The manufacturer, by distilling his coal, instead of burning it as it comes from the pit, will save his candles and improve his fuel. One effort at the outset, in erecting a proper apparatus, will reduce his annual disbursement, for these two articles of prime necessity,much in the same manner, (though in a far greater degree) as the farmer gains by building a thrashing machine and laying aside the use of the flail.
The principal expence in the pursuit of this branch of civil and domestic economy is therefore the dead capital employed in erecting the machinery destined for preparing and conveying the gas; the floating or live capital is comparatively small. At the same time, were we to offer an advice to the public on this subject, it would be, that no private individual resident in London should attempt to light his premises for the sake of economy with coal-gas by means of his own apparatus, whose annual expence for light does not exceed 60l. because the expence of erecting and attending a small apparatus is almost as great as one constructed on a larger scale would be. For if the quantity of gas wanted is not sufficient to keep the retorts continually in a red-hot or working state, the cost of the gas will be considerably enhanced; because either the empty retorts must be continued red-hot, or the fire must be suffered to go out; and the retorts, when cold, cannot bebrought to a working state, that is to say, be made red hot again, but at a considerable expence of fuel, which must be wasted to no purpose. Whereas, if the retorts are constantly kept red hot and in action, one half of the coal necessary to produce a given quantity of gas will then be saved. But when a street, or a small neighbourhood is wanted to be lighted, and the retorts can always be kept in a working state, that is to say, red hot, the operation may be commenced with safety; because the sum required for erecting the apparatus, and the labour attending it, together with the interest of money sunk, will then soon be liquidated by the light which it will afford.
Individuals, therefore, may engage in the distillation of coal, and trade with advantage in the articles produced by that process, and the lighting of cities may be accomplished without the aid of incorporated bodies; and parishes may be lighted by almost as many individuals as there are streets in a parish.
From experiments, made by Mr.Clegg, on the effects produced by a number of gas-lights, of a certain intensity, there is reason to believethat the streets of small towns might be illuminated at a cheaper rate, by means of a tower, or pagoda, furnished with gas-lamps, than can be done in the ordinary way by street lamps: the gas being conducted to the top of the building from the apparatus below, and the light directed down again, upon the objects to be illuminated, by means of reflectors placed at a certain angle. By this contrivance, all the main pipes which convey the gas through the streets, as well as those collateral ones that branch out from them to the street lamps, would be saved, and thus compensate for the expense of the tower.
The most beneficial application of gas-lights unquestionably is in all those situations where a great quantity of light is wanted in a small place: and where light is required to be most diffused, the advantages of this mode of illumination are the least.—Hence, as already stated, the lighting of the parish, or street-lamps only, without lighting shops or houses, can never be accomplished with economy.
We have noticed before the reason why the price of coals can have little effect upon the gas-light; because the very refuse, or smallcoals, called slack, which pass through the screen at the pit’s mouth, and which cannot be brought into the market—nay, even the sweepings of the pit, which are thrown away, may be employed for the production of coal-gas. It makes no difference in what form the coal is used, and this circumstance may contribute to enable the coal-merchant to furnish coals in larger masses, and as they come from the mine, instead of increasing the bulk by breaking them into a smaller size,[33]which is a practice commonlyadhered to. This unquestionably reduces the value of coals; because the quantity of radiant heat generated in the combustion of a given quantity of any kind of fuel depends much upon the management of the fire, or upon the manner in which the fuel is consumed. When the fire burns bright, much radiant heat will be sent off from it; but whenit is smothered up, very little will be generated: most of the heat produced will then be expended in giving elasticity to a thick dense vapour, or smoke, which is seen rising from the fire; and the combustion being very incomplete, the carburetted hidrogen gas of the coal being driven up the chimney without being inflamed, the fuel is wasted to little purpose.
[33]It is not generally apprehended, how very wasteful the use of small coals is in the ordinary open fire-grates. Necessity makes us use the poker very much, particularly, when the coals are small; and habit prevails even when they are large. By the constant stirring of the fire almost the whole of the small coal passes through the bars; and consequently a great deal goes to the dust-hole without being burnt at all. To prove this, we need only take a shovel full of ashes and put them into a pail, and then pouring water over them, which being gently run off, will carry away nearly all the light and burnt parts: and leave an astonishing quantity of bright unburnt coal, which has escaped from the fire-place, in consequence of being small.When the grate of the fire-place is large, and the small coals are thrown behind; or when we can have patience enough to bear the cold for an hour or two, or contrive to have the fire lighted a long time before we want it, the small coal may be of some use, but the fire made with it is never strong, nor so bright; and does not burn so long as a fire made with large or round coals: it often requires the help of the poker, and produces a great quantity of breeze.The loss in the use of small coals is more considerable to the poor, who cannot keep large fires. When they want their breakfast or dinner, the time they can spare is limited; and to have their water sooner boiling, or their meals quicker ready; they must make use of the poker, and lose a great deal of coal. This fact is so evident, that any body who wishes to make the experiment before recommended, will find that much more bright coal goes to the dust-hole of the poor man, than to the dust-hole of a rich family, where, the fire-place being large, the small coal has more chance of burning.The loss is still greater to the poor, in consequence of the inferior sorts of coal which are sold to them. If it is the light sort, it burns too quick, and they consume double the quantity; if the strong sort, it burns too slow, and is nearly as wasteful; for a great quantity of it then goes to the dust-hole without having been lighted at all.An incorrect opinion is often entertained, that the real quantity of coal contained in a sack is lessened by separating or screening the small from the round coals; but we must recollect, that any compact body occupies less space than is required to contain the same matter, reduced to smaller irregular pieces, or to powder.—Now the screening only takes away the finest dusty part of the coals, and admits more small pieces of round coals to be filled into the sack.
[33]It is not generally apprehended, how very wasteful the use of small coals is in the ordinary open fire-grates. Necessity makes us use the poker very much, particularly, when the coals are small; and habit prevails even when they are large. By the constant stirring of the fire almost the whole of the small coal passes through the bars; and consequently a great deal goes to the dust-hole without being burnt at all. To prove this, we need only take a shovel full of ashes and put them into a pail, and then pouring water over them, which being gently run off, will carry away nearly all the light and burnt parts: and leave an astonishing quantity of bright unburnt coal, which has escaped from the fire-place, in consequence of being small.
When the grate of the fire-place is large, and the small coals are thrown behind; or when we can have patience enough to bear the cold for an hour or two, or contrive to have the fire lighted a long time before we want it, the small coal may be of some use, but the fire made with it is never strong, nor so bright; and does not burn so long as a fire made with large or round coals: it often requires the help of the poker, and produces a great quantity of breeze.
The loss in the use of small coals is more considerable to the poor, who cannot keep large fires. When they want their breakfast or dinner, the time they can spare is limited; and to have their water sooner boiling, or their meals quicker ready; they must make use of the poker, and lose a great deal of coal. This fact is so evident, that any body who wishes to make the experiment before recommended, will find that much more bright coal goes to the dust-hole of the poor man, than to the dust-hole of a rich family, where, the fire-place being large, the small coal has more chance of burning.
The loss is still greater to the poor, in consequence of the inferior sorts of coal which are sold to them. If it is the light sort, it burns too quick, and they consume double the quantity; if the strong sort, it burns too slow, and is nearly as wasteful; for a great quantity of it then goes to the dust-hole without having been lighted at all.
An incorrect opinion is often entertained, that the real quantity of coal contained in a sack is lessened by separating or screening the small from the round coals; but we must recollect, that any compact body occupies less space than is required to contain the same matter, reduced to smaller irregular pieces, or to powder.—Now the screening only takes away the finest dusty part of the coals, and admits more small pieces of round coals to be filled into the sack.
Nothing can be more perfectly devoid of common sense, and wasteful and slovenly at the same time, than the manner in which chimney fires, where coals are burnt, are commonly managed by servants. They throw on a load of (perhaps all small) coals at once, through which the flame is hours in making its way; and frequently it is not without much care and trouble that the fire is prevented from going quite out. During this time no heat is communicated to the room; and, what is still worse, the throat of the chimney being occupied merely by a heavy dense vapour, not possessed of any heating power, and, consequently, not having much elasticity, the warm air of the room finds less difficulty in forcing its way up the chimney and escaping,than when the fire burns bright, and the coal-gas is ignited. And it happens not unfrequently, especially in chimnies and fire-places ill-constructed, that this current of warm air from the room which presses into the chimney, crossing upon the current of heavy smoke and aqueous vapour which escapes slowly from the fire, obstructs it in its ascent, and beats it back into the room. Hence it is that chimnies so often smoke when too large a quantity of fresh coals is put upon the fire. So many coals should never be put on the fire at once as to prevent the free passage of the flame between them, or to prevent them becoming quickly heated, so as to give out the carburetted hidrogen gas which they are capable of furnishing, and to cause it to be inflamed, In short, a fire should never be smothered: and when attention is paid to the quantity of coals put on, there is little use for the poker; and this circumstance will contribute much to cleanliness, and the preservation of furniture.
The author of a paper in the Plain Dealer asserts, that, of the various perversions of abilities, there is none that makes a human being more ridiculous, than that of attemptingto stir a fire without judgment; to prevent which he lays down the following rules:—1. Stirring of a fire is of use, because it makes a hollow where, the air being rarefied by the adjacent heat, the surrounding air rushes into this hollow, and gives life and support to the fire, and carries the flame with it. 2. Never stir a fire when fresh coals are laid on, particularly when they are very small, because they immediately fall into the hollow place, and therefore ruin the fire. 3. Always keep the bottom bars clear. 4. Never begin to stir the fire at the top, unless when the bottom is quite clear, and the top only wants breaking.
There is one subject more on which it is necessary to speak.—In the present instance, the public has been alarmed by representations that the general adoption of gas-lights would expose us to innumerable accidents, from the inflammable nature of the gas, and the explosion of the apparatus in which it is prepared, or the bursting of the pipes by which it is conveyed. But there is no ground for such fears.
Those who are familiar with the subject will readily allow, that there is no more riskin the action of a gas-light machinery, properly constructed, than there is in the action of a steam-engine, built on just principles.
The manufacture of the coal-gas requires nothing more than what the most ignorant person, with a common degree of care and attention, is competent to perform. The heating of the gas-furnace, the charging of the retorts with coal, the closing them up air-tight, the keeping them red-hot, and discharging them again, are the only operations required in this art; and these, surely, demand no more skill than a few practical lessons can teach to the meanest capacity. The workman is not called upon to exercise his own judgment, because, when the fire is properly managed, the evolution of the gas goes on spontaneously, and without further care, till all the gas is extricated from the coal.
No part of the machinery is liable to be out of order,—there are no cocks to be turned, no valves to be regulated; nor can the operator derange the apparatus but by the most violent efforts. And when the stock of gas is prepared, we may depend on its lighting power as muchas we depend on the light to be obtained from a certain number of candles or oil-lamps.
The diversified experiments which have been made by different individuals, unconnected with each other, have sufficiently established the perfect safety of the new lights; and numerous manufactories might be named in which the gas-lights have now been in use for upwards of seven years, where nothing like an accident has occurred, though the apparatus in all of them is entrusted to the most ignorant man.
It would be easy to state the causes which have given rise to some of those accidents that have spread alarm amongst the public; but of this it is not my business to speak at length. It is sufficient, on the present occasion, to state, that those melancholy occurrences which have happened at some gas-light establishments which I have had an opportunity of examining, were totally occasioned by egregious failures committed in the construction of the machinery. Thus, an explosion very lately took place in a manufactory lighted with coal-gas, in consequence of a large quantity of gas escaping into abuilding, where it mingled with common air, and was set on fire by the approach of a lighted candle. That such an accident could happen, is an evident proof that the machinery was erected by a bungler, unacquainted with the most essential principles of this art; because such an accident might have been effectually prevented, by adapting a waste pipe to the gasometer and gasometer house. By this means, if more gas had been prepared than the gasometer would contain, the superfluous quantity could never have accumulated, but would have been transported out of the building into the open air, in as an effectual manner as the waste-pipe of a water cistern conveys away the superfluous quantity of water, when the cistern is full. Such an expedient did not form part of the machinery.
Other instances might be named, where explosions have been occasioned through egregious mistakes having been committed in the erection of the gas-light machinery, were this a subject on which I meant to treat.
That the coal-gas, when mixed with a certain portion of common air, in close vessels, may be inflamed by the contact of a lightedbody, as has been stated,page 98, is a fact sufficiently known. But the means of preventing such an occurrence in the common application of gas-lights, are so simple, easy, and effectual, that it would be ridiculous to dread danger where there is nothing to be apprehended. In speaking thus of the safety of the gas-light illumination, I do not mean to deny that no possible circumstances may occur where the coal-gas may be the cause of accident. It is certain that the gas, when suffered to accumulate in large quantities in close and confined places, where there is no current of air, such as in cellars, vaults, &c. and where it can mix with common air, and remain undisturbed, that it may be liable to take fire when approached by a lighted body; but I do not see how it is probable that such an accumulation of gas should take place in the apartments of dwelling houses. The constant current of air which passes continually through the rooms, is sufficient to prevent the possibility of such an accumulation ever to take place. And with regard to the bursting of the pipes which convey the gas, no accident can possibly happen from that quarter; because thegas which passes through the whole range of pipes sustains a pressure equal to the perpendicular weight of about one inch of water only, and such a weight of course is insufficient to burst iron pipes. Nor could the town when illuminated by gas-lights, be thrown suddenly into darkness, as has been asserted might happen by the fracture of a main pipe, supposing such an event should take place; because the lateral branches, which supply the street-lamps and houses, are supplied by more than one main; and the consequence of a fracture would be only an extinction of the few lamps in the immediate vicinity of the broken pipe, because the rest of the pipes, situated beyond the fracture, would continue to be supplied with gas from the other mains, as will become obvious from the sketch exhibited in the next page.