PART II. (continued 2)

The oil and ammoniacal water which distil over do not mix, so that they may be easily separated by decantation. The oil is a yellowish inferior kind of oil of turpentine, which is very useful in painting ships, for making varnishes, and other coarse out-door work.

Two hundred pounds of tar produce, upon an average, fifty-three pounds of essential oil.

If the coal-tar is wanted to be converted into pitch, without obtaining the oil which it is capable of furnishing, the evaporation of it may be performed in a common boiler; but as it is extremely liable to boil over, the greatest precaution is necessary in conducting the evaporation. A boiler constructed on the following plan is very convenient for the conversion of coal-tar into pitch. The contrivance consists in adding a spout, or rim, to the common boiler, into which the tar spreads itself as it rises, and by this means becomes cooled, and the boiling over is checked.

Kettle for boiling Tar.

1000lb. of coal-tar produce, upon an average, from 460 to 480lb. of pitch. A subsequent fusion, with a gentle heat, converts the coal-pitch into a substance possessing all the characters of asphaltum.

Ammoniacal Fluid.—The properties of the ammoniacal liquor, which accompanies the tar, and which is deposited in the tar-cistern, has not yet been fully investigated. It is employed already in the manufacture of muriate of ammonia (sal ammoniac). One chaldron of coal affords from 220 to 240lb. of this ammoniacal fluid, which is composed chiefly of sulphate, and carbonate of ammonia.—Such are the products obtainable from coal.

However certain the practicability of extending the new lights to the dwelling houses of every town and village is, it cannot be expected that such an event should take place speedily and generally. To eradicate prejudice, and to alter established habits, is a work which nothing but time can effect; because prejudice is the effect of habit, and can seldom be eradicated from the minds of such individuals as consider the ready occurrence of a proposition as a test of its truth. To establish a new philosophical theory has, in every instance, required time sufficient to educate an entire generation of men. The rejection of the Aristotelian philosophy—the adoption of experimental research—the substitution of the doctrine of gravitation instead of that of vortices, and the rejection of phlogiston by modern chemists, are sufficiently illustrative of this assertion. New arts, and new practices, are still more difficult to be introduced. The new art of bleaching need merely be mentioned to prove this assertion. The new grammar—the new rudiments of science—the new stile—or the new instrument, however superior to the old in simplicity, facility, and truth, must be less valuable to the ordinary teacher or artisan, whose memory is familiarized with the precepts of the latter, and whose only ambition is to earn his subsistence with the least possible exertion.

The slowness with which improvements of every kind, make their way into common use, and especially such discoveries as are most calculated to be of an extended or general utility is very remarkable, and forms a striking contrast to the extreme avidity with which those unmeaning changes are adopted, which folly and caprice are continually sending forth into the world under the auspices of fashion.

On the first view of the subject it appears very extraordinary, that any person should neglect, or refuse to avail himself of a proposed invention, or improvement, which is evidently calculated to economise his labour, and to encrease his comforts; but when we reflect on the power of habit, and consider how difficult it is for a person even to perceive the disadvantages or imperfections of former modes to which he has been accustomed from his early youth, our surprize will be diminished, or vanish altogether.

Many other circumstances, besides prejudice, are unfavourable to the introduction of new and useful discoveries. Among these jealousy, malice, envy, and revenge, have too often their share in obstructing the progress of real improvement, and in preventing the adoption of plans evidently calculated to promote the public good.

A plan like the present, which proposes not only to trench upon domestic habits, but to give an entire new direction to a portion of the skill and capital of the country, must necessarily encounter the most strenuous opposition. It is thus that some individuals have mustered all their strength against the introduction of this new art. An endeavour has been made to move the public opinion by dismal forebodings of the Greenland trade, and the subsequent loss of a nursery of British seamen. This objection is nothing more than the common clamour that is always set up against every new means of abridging labour, to which had the public listened, an interdict would have been laid upon the spinning and threshing machines, the steam engine, and a thousand other improvements in machinery.

Indeed such clamour scarcely ever fails to be made when the extension of machinery and the abridgement of labour or the application of inanimate powers are considered. On such occasions, it is stated by certain humane but mistaken objectors, that the scheme of mechanical and chemical improvement is pointed against the human species—that it tends to drive them out of the system of beneficial employment—that the introduction of machinery is injurious to the labouring class of society, by abridging their work. Two creatures offer themselves for employment and support—a man and a horse. I must invariably prefer the latter, and leave the former to starve. Two other beings—a horse and a steam-engine, are candidates for my favour. My preference to the latter tends to exterminate the species of the former. In both cases it is stated, that the number of intelligent creatures capable of the enjoyment of happiness must be diminished for want of support; and that, on the whole, the sum of the proposed improvement is not only a less proportion of good to society, but a positive accession of misery to the unemployed poor.

On this wide and extended argument, which can in fact be maintained against all improvements whatever in no other way than by insisting that the savage state of man, with all its wants, its ignorance, its ferocity, and its privations, is preferable to the social intercourse of effort and division of labour we are habituated to prefer, it may be sufficient to observe that it includes matter not only for reasoning and induction, but also for experiment. By reference to the matter of fact, though it must be allowed that new improvements, which change the habits of the poor, must at first expose them to a temporary inconvenience and distress, against which, in fairness, it is the duty of society to defend them; yet the invariable result of such improvements is always to better the condition of mankind. A temporary inconvenience to individuals must often be incurred for the sake of general national benefit.

It is to manufactories carried on by machinery and to the abridgment of labour, that this country is indebted for her riches, her independence and pre-eminent station among the nations of the world.

But let us return to the subject.—The progress of the new mode of lighting with coal-gas can never wholly supersede the use of candles and moveable lights. The objection with regard to the Greenland trade is equally futile. This traffic, might with more propriety be called a drain, than a nursery, of the naval force. The nature of the Greenland service requires that the crew should consist chiefly of able-bodied sailors; and being protected men, not subject to the impress law, they are thus rendered useless for national defence. The nursery of British seamen is the coasting trade; and if the gas-light illumination be put in practice to a large extent, it will increase that trade as much as it will diminish the Greenland fishery.

Even on the extreme supposition that it would annihilate the Greenland fisheries altogether, we should have no reason to regret the event. The soundest principles of political economy must condemn the practice of fitting out vessels to navigate the polar seas for oil, if we can extract a superior material for procuring light at a cheaper rate from the produce of our own soil.

Indeed the fisheries will find ample encouragement, and the consequence of lighting our streets with gas can prove injurious only to our continental friends, one of whose staple commodities, tallow, we shall then have less occasion to purchase.

There will be less waste indeed, but a greater consumption of coal. The lower classes of the community are at present very scantily supplied with firing; and nothing but a reduction of price is necessary to increase to a very large amount the whole average quantity of fuel consumed in the country. The lightness of the coke produced in the gas-light manufacture diminishing the expence of land carriage, will facilitate its general diffusion—the comforts of the poor will be materially augmented, and a number of useful operations in agriculture and the arts be carried on, which are now checked and impeded by the price of fuel.

If any additional want were wanted for the coke it will readily be found in the continental market; coke being much better suited than coal to the habits of most European nations.

The gas-light illumination cannot tend to diminish the coal-trade; on the contrary it will prove beneficial to it; it will contribute to lower the price of the superior kinds of coal, and keep a level which cannot be shaken under any circumstances; it will contribute to prevent combinations which do certainly operate to the prejudice of the public, and do sometimes put this great town at the mercy of particular proprietors in the north, who deal out coal in the way they please. The competition thus produced, it is impossible not to consider as an advantage, which would prevent in future such combinations, and put those in London out of the reach of them.

It is worthy observation, that the annual importation of coal into this Metropolis, is above one million and eighty-eight thousand chaldrons.[31]

It may be objected to the universality of our conclusion, that the price of coals, differing very much in different places, will occasion a variation in the expence of the new mode of illumination. But there are two reasons why this should have less place, because we find, in Mr. Murdoch’s statement, page 69, that of 600l. the estimated yearly expence of lighting the cotton mill, 550l. consist of interest of capital, and tear and wear of apparatus, leaving the cost of coal only 50l. a sum so trifling, when we reflect that it replaces 2000l. worth of candles, that the price of coal, even where it is highest, can but slightly affect the general profits.[32]

2dly, The coal, by yielding the gas and other products,—namely, tar, pitch, ammoniacal liquor, &c. of which we have treated already, is converted into a substance, increased in bulk, and in the power of producing heat, namely, coke; and as a manufactory generally requires heating as well as lighting, there will be a gain both ways. The manufacturer, by distilling his coal, instead of burning it as it comes from the pit, will save his candles and improve his fuel. One effort at the outset, in erecting a proper apparatus, will reduce his annual disbursement, for these two articles of prime necessity, much in the same manner, (though in a far greater degree) as the farmer gains by building a thrashing machine and laying aside the use of the flail.

The principal expence in the pursuit of this branch of civil and domestic economy is therefore the dead capital employed in erecting the machinery destined for preparing and conveying the gas; the floating or live capital is comparatively small. At the same time, were we to offer an advice to the public on this subject, it would be, that no private individual resident in London should attempt to light his premises for the sake of economy with coal-gas by means of his own apparatus, whose annual expence for light does not exceed 60l. because the expence of erecting and attending a small apparatus is almost as great as one constructed on a larger scale would be. For if the quantity of gas wanted is not sufficient to keep the retorts continually in a red-hot or working state, the cost of the gas will be considerably enhanced; because either the empty retorts must be continued red-hot, or the fire must be suffered to go out; and the retorts, when cold, cannot be brought to a working state, that is to say, be made red hot again, but at a considerable expence of fuel, which must be wasted to no purpose. Whereas, if the retorts are constantly kept red hot and in action, one half of the coal necessary to produce a given quantity of gas will then be saved. But when a street, or a small neighbourhood is wanted to be lighted, and the retorts can always be kept in a working state, that is to say, red hot, the operation may be commenced with safety; because the sum required for erecting the apparatus, and the labour attending it, together with the interest of money sunk, will then soon be liquidated by the light which it will afford.

Individuals, therefore, may engage in the distillation of coal, and trade with advantage in the articles produced by that process, and the lighting of cities may be accomplished without the aid of incorporated bodies; and parishes may be lighted by almost as many individuals as there are streets in a parish.

From experiments, made by Mr. Clegg, on the effects produced by a number of gas-lights, of a certain intensity, there is reason to believe that the streets of small towns might be illuminated at a cheaper rate, by means of a tower, or pagoda, furnished with gas-lamps, than can be done in the ordinary way by street lamps: the gas being conducted to the top of the building from the apparatus below, and the light directed down again, upon the objects to be illuminated, by means of reflectors placed at a certain angle. By this contrivance, all the main pipes which convey the gas through the streets, as well as those collateral ones that branch out from them to the street lamps, would be saved, and thus compensate for the expense of the tower.

The most beneficial application of gas-lights unquestionably is in all those situations where a great quantity of light is wanted in a small place: and where light is required to be most diffused, the advantages of this mode of illumination are the least.—Hence, as already stated, the lighting of the parish, or street-lamps only, without lighting shops or houses, can never be accomplished with economy.

We have noticed before the reason why the price of coals can have little effect upon the gas-light; because the very refuse, or small coals, called slack, which pass through the screen at the pit’s mouth, and which cannot be brought into the market—nay, even the sweepings of the pit, which are thrown away, may be employed for the production of coal-gas. It makes no difference in what form the coal is used, and this circumstance may contribute to enable the coal-merchant to furnish coals in larger masses, and as they come from the mine, instead of increasing the bulk by breaking them into a smaller size,[33] which is a practice commonly adhered to. This unquestionably reduces the value of coals; because the quantity of radiant heat generated in the combustion of a given quantity of any kind of fuel depends much upon the management of the fire, or upon the manner in which the fuel is consumed. When the fire burns bright, much radiant heat will be sent off from it; but when it is smothered up, very little will be generated: most of the heat produced will then be expended in giving elasticity to a thick dense vapour, or smoke, which is seen rising from the fire; and the combustion being very incomplete, the carburetted hidrogen gas of the coal being driven up the chimney without being inflamed, the fuel is wasted to little purpose.

Nothing can be more perfectly devoid of common sense, and wasteful and slovenly at the same time, than the manner in which chimney fires, where coals are burnt, are commonly managed by servants. They throw on a load of (perhaps all small) coals at once, through which the flame is hours in making its way; and frequently it is not without much care and trouble that the fire is prevented from going quite out. During this time no heat is communicated to the room; and, what is still worse, the throat of the chimney being occupied merely by a heavy dense vapour, not possessed of any heating power, and, consequently, not having much elasticity, the warm air of the room finds less difficulty in forcing its way up the chimney and escaping, than when the fire burns bright, and the coal-gas is ignited. And it happens not unfrequently, especially in chimnies and fire-places ill-constructed, that this current of warm air from the room which presses into the chimney, crossing upon the current of heavy smoke and aqueous vapour which escapes slowly from the fire, obstructs it in its ascent, and beats it back into the room. Hence it is that chimnies so often smoke when too large a quantity of fresh coals is put upon the fire. So many coals should never be put on the fire at once as to prevent the free passage of the flame between them, or to prevent them becoming quickly heated, so as to give out the carburetted hidrogen gas which they are capable of furnishing, and to cause it to be inflamed, In short, a fire should never be smothered: and when attention is paid to the quantity of coals put on, there is little use for the poker; and this circumstance will contribute much to cleanliness, and the preservation of furniture.

The author of a paper in the Plain Dealer asserts, that, of the various perversions of abilities, there is none that makes a human being more ridiculous, than that of attempting to stir a fire without judgment; to prevent which he lays down the following rules:—1. Stirring of a fire is of use, because it makes a hollow where, the air being rarefied by the adjacent heat, the surrounding air rushes into this hollow, and gives life and support to the fire, and carries the flame with it. 2. Never stir a fire when fresh coals are laid on, particularly when they are very small, because they immediately fall into the hollow place, and therefore ruin the fire. 3. Always keep the bottom bars clear. 4. Never begin to stir the fire at the top, unless when the bottom is quite clear, and the top only wants breaking.

There is one subject more on which it is necessary to speak.—In the present instance, the public has been alarmed by representations that the general adoption of gas-lights would expose us to innumerable accidents, from the inflammable nature of the gas, and the explosion of the apparatus in which it is prepared, or the bursting of the pipes by which it is conveyed. But there is no ground for such fears.

Those who are familiar with the subject will readily allow, that there is no more risk in the action of a gas-light machinery, properly constructed, than there is in the action of a steam-engine, built on just principles.

The manufacture of the coal-gas requires nothing more than what the most ignorant person, with a common degree of care and attention, is competent to perform. The heating of the gas-furnace, the charging of the retorts with coal, the closing them up air-tight, the keeping them red-hot, and discharging them again, are the only operations required in this art; and these, surely, demand no more skill than a few practical lessons can teach to the meanest capacity. The workman is not called upon to exercise his own judgment, because, when the fire is properly managed, the evolution of the gas goes on spontaneously, and without further care, till all the gas is extricated from the coal.

No part of the machinery is liable to be out of order,—there are no cocks to be turned, no valves to be regulated; nor can the operator derange the apparatus but by the most violent efforts. And when the stock of gas is prepared, we may depend on its lighting power as much as we depend on the light to be obtained from a certain number of candles or oil-lamps.

The diversified experiments which have been made by different individuals, unconnected with each other, have sufficiently established the perfect safety of the new lights; and numerous manufactories might be named in which the gas-lights have now been in use for upwards of seven years, where nothing like an accident has occurred, though the apparatus in all of them is entrusted to the most ignorant man.

It would be easy to state the causes which have given rise to some of those accidents that have spread alarm amongst the public; but of this it is not my business to speak at length. It is sufficient, on the present occasion, to state, that those melancholy occurrences which have happened at some gas-light establishments which I have had an opportunity of examining, were totally occasioned by egregious failures committed in the construction of the machinery. Thus, an explosion very lately took place in a manufactory lighted with coal-gas, in consequence of a large quantity of gas escaping into a building, where it mingled with common air, and was set on fire by the approach of a lighted candle. That such an accident could happen, is an evident proof that the machinery was erected by a bungler, unacquainted with the most essential principles of this art; because such an accident might have been effectually prevented, by adapting a waste pipe to the gasometer and gasometer house. By this means, if more gas had been prepared than the gasometer would contain, the superfluous quantity could never have accumulated, but would have been transported out of the building into the open air, in as an effectual manner as the waste-pipe of a water cistern conveys away the superfluous quantity of water, when the cistern is full. Such an expedient did not form part of the machinery.

Other instances might be named, where explosions have been occasioned through egregious mistakes having been committed in the erection of the gas-light machinery, were this a subject on which I meant to treat.

That the coal-gas, when mixed with a certain portion of common air, in close vessels, may be inflamed by the contact of a lighted body, as has been stated, page 98, is a fact sufficiently known. But the means of preventing such an occurrence in the common application of gas-lights, are so simple, easy, and effectual, that it would be ridiculous to dread danger where there is nothing to be apprehended. In speaking thus of the safety of the gas-light illumination, I do not mean to deny that no possible circumstances may occur where the coal-gas may be the cause of accident. It is certain that the gas, when suffered to accumulate in large quantities in close and confined places, where there is no current of air, such as in cellars, vaults, &c. and where it can mix with common air, and remain undisturbed, that it may be liable to take fire when approached by a lighted body; but I do not see how it is probable that such an accumulation of gas should take place in the apartments of dwelling houses. The constant current of air which passes continually through the rooms, is sufficient to prevent the possibility of such an accumulation ever to take place. And with regard to the bursting of the pipes which convey the gas, no accident can possibly happen from that quarter; because the gas which passes through the whole range of pipes sustains a pressure equal to the perpendicular weight of about one inch of water only, and such a weight of course is insufficient to burst iron pipes. Nor could the town when illuminated by gas-lights, be thrown suddenly into darkness, as has been asserted might happen by the fracture of a main pipe, supposing such an event should take place; because the lateral branches, which supply the street-lamps and houses, are supplied by more than one main; and the consequence of a fracture would be only an extinction of the few lamps in the immediate vicinity of the broken pipe, because the rest of the pipes, situated beyond the fracture, would continue to be supplied with gas from the other mains, as will become obvious from the sketch exhibited in the next page.

Main pipe, leading from the Gas-light station or apparatus, situated in Brick Lane, near Old St.[34]

Main pipe, leading from the gaslight apparatus, or station, at Norton Falgate.[35]

Main pipe, leading from the gaslight apparatus, or station, in Westminster.[36]

The black lines represent the gas-light mains, or largest pipes, from which the smaller pipes branch off: they are connected with each other at the places marked A B C; and the dotted lines represent the smaller mains, or collateral branches before-mentioned. The main pipes are all furnished with valves, or cocks, placed at about 100 feet distant from each other. Now let us suppose that a main pipe, in any part of the street marked in the sketch, Pall Mall, should break, it is evident, on mere inspection, that the gas which is passing through the main in the Strand, and which is also connected with the main in the Haymarket, Piccadilly, and Coventry Street, would continue to supply the broken pipe, and the valve nearest to the fracture being shut, would prevent the loss of any considerable quantity of gas, and the few lamps situated between the two valves and the fracture would therefore only become extinguished.

Further, let us suppose a main pipe should break in Piccadilly; in that case, the valve being shut on each side of the fracture, the gas would be supplied from the mains in the Haymarket and St. James’s Street. And the same effect would be produced in any part of the town, supplied with gas-pipes. Besides all this, in the statement thus far given, we have assumed that all the gas-light mains are supplied with gas from one manufacturing station only, but which in reality is not the case. The range of pipes that convey the gas is connected with three gas-light establishments, situated at different parts of the town; and the gas which is supplied from these stations is connected with the whole system of pipes in the streets.[37] If, therefore, one of the manufactories should be annihilated, it would make no difference, because the lights would be amply supplied from the other two manufacturing stations. Hence it is obvious, that the fracture of any of the gas-light mains, or even the total destruction of one or more of the manufactories themselves, would be attended with no serious consequence; and as the system of lighting with gas becomes more extended, the manufactories, or stations for supplying it, will also be multiplied, to give effect and security to the whole.

In fact, no danger can arise from the application of gas-lights in any way, but what is common to candle-light, and lamps of all kinds, and is the fault of none of them. Even in this case the gas-lights are less hazardous. There is no risk of those accidents which often happen from the guttering or burning down of candles, or from carelessly snuffing them. The gas-light lamps and burners must necessarily be fixed to one place, and therefore cannot fall, or otherwise become deranged, without being immediately extinguished. Besides, the gas-light flames emit no sparks, nor are any embers detached from them. As a proof of the comparative safety of the gas-lights, it need only be stated, that the Fire-offices engage themselves to insure cotton-mills, and other public works, at a less premium, where gas-lights are used, than in the case of any other lights.[38] The excessive expence of insurance arising from the numerous candles employed in most of the first rate manufactories, and the combustible nature of the structure of the buildings; the great difficulty of retrieving the injury resulting to a well-organised business, from the accidental destruction of the machinery, are objects alone sufficient to furnish the strongest economical, as well as political recommendations, for the adoption of the new lights in all manufactories where work is done by candle-light.

After considering the facts so far detailed, many other advantages, connected with the gas-light illumination, will naturally suggest themselves to the reader. I have endeavoured merely to point out the leading characters of the new lights, as they are at present. Ingenious men may speculate from what has been done to what remains to be effected, which, no doubt, will embrace objects of the greatest utility and most extended national importance. The public attention is awakened to the new properties of coal, and will not rest till they are extensively applied to economical purposes. The consequence will be, a considerable defalcation in the revenue. For, in proportion as the gas-lights are more or less generally adopted in all towns of the country, the consumption of oil and tallow will be diminished, and the impost on those articles become less productive; and when this takes place, Government, no doubt, will share in the profits, by levying a tax on the new lights. The Exchequer will thus have nothing to fear; as one branch of the revenue fails, another, and a more productive one, will supply its place.

Upon the whole, when we reflect that the object of the gas-light illumination is to open a source of national wealth, of which nothing can deprive us, to create, we may almost say, new articles of value, its friends cannot be thought guilty of great presumption, if they look forward with confidence to the successful extension of this new art of civil economy; and if, contrary to all expectations, the effects of jealousy and prejudice should, in some respect or other, continue here and there its influence against this new art of procuring light, a firm perseverance of its application must at length remove that ignorance which alone can give them birth.

TABULAR VIEW,

EXHIBITING

The quantity of Gas, Coke, Tar, Pitch, Essential Oil, and Ammoniacal Liquor, obtainable from a given quantity of Coal; together with an Estimate of the quantity of Coal necessary to produce a quantity of Gas, capable of yielding a Light equal in duration of time and intensity to that produced by Tallow Candles of different kinds.

Cost of Coal. Weight of Coal. Produce of Gas, in cubic feet. - [39]Equal to as many tallow candles, 12 in the pound, burning two hours; or to Candles.

Mini- mum. Maxi- mum. Aver- age. Min. Max. Aver. Min. Max. Aver. 9,516 8,651 11 10 to the pound. to thdo.

One Chal. of Coal, from 25 to 28 cwt. - 40 s to 60 s — 50 s 2,800 to 3,136 — 2,968 8,906 to 11,872 — 10,388 [39] 7,786 6,921 6,556 5,194 10 9 8 7 to thdo. to thdo. to thdo. to thdo.

One Ton 30 s to 48 s — 38 s 6 d 2,240 6,720 to 8,960 — 7,840 4,325 5 to thdo.

One Sack 3 s 4 d to 5 s — 4 s 2 d 233 to 261 — 247 741 to 988 — 814 3,463 4 to thdo.

One Bushel 1 s 2 d to 1 s 8 d — 1 s 5 d 78 to 87 — 82 ¹⁄₂ 247 to 330 — 290 2,595 3 to thdo.

One Peck 3 ¹⁄₂ to 5 d — 4 ¹⁄₄ 19 ¹⁄₂ to 21 ¹⁄₄ — 20 ¹⁄₄ 61 to 82 — 71 ¹⁄₂ 1,730 2 to thdo.

One Pound ¹⁄₄ 1 3 to 4 — 3 ¹⁄₂ 866 1 to thdo.

Coke.—One chaldron of coal, from 25 to 28 cwt. gives 1¹⁄₄ to 1½ chaldron of Coke.

Tar.—One chaldron of coal, from 25 to 28 cwt. gives from 150 to 180lb. of Tar,[39] or 15 to 18 ale gallons, 10lb. each.

Ammoniacal Liquor.—One chaldron of coal, gives from 220 to 240lb. of Ammoniacal Liquor, or 22 to 24 ale gallons.

Tabular View, exhibiting the illuminating power of Coal-Gas, compared with the illuminating power of Tallow Candles of different sizes.

One chaldron of Coal produces, according to weight and quality,

Burning. Candles. 12 to 1lb. 6 to 1lb.

Cubic feet of Gas. Average. 1 hour = 21,000 = 10,500

From 9,000 to 12,000 10,500 2 hours = 10,500 = 5,250

6,000 8,000 7,000 3 ditto = 7,000 = 3,500

4,500 6,000 5,250 4 ditto = 5,250 = 2,625

3,600 4,800 4,400 5 ditto = 4,400 = 2,200

3,000 4,000 3,500 6 ditto = 3,500 = 1,750

2,571 3,428 3,005 7 ditto = 3,005 = 1,502

2,250 3,000 2,625 8 ditto = 2,625 = 1,312

2,000 2,666 2,333 9 ditto = 2,333 = 1,166

1,800 2,100 2,100 10 ditto = 2,100 = 1,050

1,636 2,191 1,913 11 ditto = 1,913 = 956

1,500 2,000 1,750 12 ditto = 1,750 = 875

1,384 1,846 1,615 13 ditto = 1,615 = 807

1,285 1,714 1,499 14 ditto = 1,499 = 749

1,200 1,600 1,400 15 ditto = 1,400 = 700

1,125 1,500 1,312 16 ditto = 1,312 = 656

1,058 1,111 1,234 17 ditto = 1,234 = 617

1,000 1,333 1,166 18 ditto = 1,166 = 583

947 1,263 1,105 19 ditto = 1,105 = 552

900 1,200 1,050 20 ditto = 1,050 = 525

857 1,143 1,000 21 ditto = 1,000 = 500

818 1,095 956 22 ditto = 956 = 478

783 1,044 913 23 ditto = 913 = 456

750 1,000 875 21 ditto = 875 = 437

N. B. If it be required to know, for how many hours one pound, or one peck, or one bushel, or one sack, of coal will produce Gas Light equal to that of a certain number of well-snuffed Tallow Candles, the proportion of each of the average weights of a pound, peck, bushel, or sack, to that of the average weight of a chaldron of coal, is as follows:

1 lb. = 2968th part of a chaldron.

One peck 20 = 148th ditto.

One bushel 82 = 36th ditto.

One sack 248 = 12th ditto.

Rule.—Divide with either of the above parts of weight, the number of lights opposite to their hours, and the product will be the number of lights burning for the same number of hours.

Example.—To know how many lights one peck of coal will give for six hours, divide the 148th part in 3,500, opposite to the number of six hours, the product is almost 24 lights. The same rule holds good for any given quantity or number of pounds of coal, in a chaldron, to find how many lights, or candles, 12 to the lb. or 6 to the lb. they will give for a given number of hours.

DESCRIPTION OF THE GAS-LIGHT APPARATUS.

PLATE I.

Exhibits a perspective view of a gas-light apparatus,[40] for lighting factories, or small districts of houses. It consists of the following parts: which may be considered separately.

Fig. 1. The Retort Furnace, for distilling the coals. It is built of brick-work. The bricks which are exposed to the immediate action of the fire, are Welch tumps, or fire-bricks; they are bedded in clay, or Windsor loam.

Fig. 2. The Tar Cistern, to collect the coal-tar, and other condensible products obtained during the distillation of the coals. It is a cast-iron hollow cylinder, closed at the top with a cast-iron cover, which has a very small hole to allow the air to escape as the liquid enters into the vessel.

Fig. 3. The Lime Machine, for purifying the crude coal-gas, and to render it fit for use. The construction of this machine will be explained in plate VII. It is put together of cast-iron plates.

Fig. 4. The Gasometer, for collecting and preserving the purified gas, and for distributing and applying it as occasion may require. It consists of two principal parts—namely, a large interior vessel closed at the top and open at the bottom, made of sheet iron, designed to contain the gas, and an outer cistern or vessel, of rather greater capacity, constructed of cast-iron plates, in which the former vessel is suspended. The latter contains the water by which the gas is confined. The interior vessel which contains the gas is suspended by chains hung over wheels or pullies, to which weights are attached, so as to be just sufficient to balance the weight of the gasometer, all but a small difference, and allowing its slow descent in the manner which is found as nearly adapted as can be to the proper supply of the lamps. The weight of the chains must be equal to the specific gravity of the material of which the gasometer is composed, so as to compensate accurately for the quantity of water which the gasometer displaces, or what is the same, it must be equal to the loss of weight which the gasometer sustains, when immersed in the water; and the counterpoise weight must be equal (or nearly so) to the absolute weight of the gasometer.

The action of these different parts of the apparatus will be obvious from the following explanation:

A, A, are two iron retorts, placed horizontally, and side by side, in the furnace; the mouth of the retorts where the coals are introduced, projects into an arched chamber, situated in front of the furnace, as shewn in the drawing by the broken down brick-work. The object of suffering the mouth of the retorts to project into a separate chamber, is merely to discharge with convenience the red hot coke from the retorts when the process is at an end; the coke being suffered to fall to the bottom of the chamber, where it cools, without becoming troublesome to the operator. It may be removed from this fire-safe chamber by the door represented at the end view of the furnace.

When the operation commences, the inner vessel of the gasometer, fig. 4 is sunk down, to expel the air which it contains to a level with the exterior vessel, or outer cistern, of the gasometer; and, consequently, becomes filled with water. As the distillation of the coal in the retorts proceeds, the liquid and gazeous products evolved from the coals are transmitted by means of the perpendicular syphon pipes B, B, into the horizontal pipe or main condenser C, with which they are connected. The liquid which is distilled, collects in the pipe, or main condenser, C, where it is retained until its quantity has risen so high as to discharge itself into the pipe D, which is connected with the upper part of one of the extremities of the condenser, C. One of the extremities of the pipes, B, B, therefore become immersed into the liquid contained in the main condenser or pipe C, whilst the vaporous or condensible fluid, after having overcome the pressure there opposed to it, is transported into the pipe E, which, after passing in a serpentine direction, E, E, &c. through the exterior vessel or cistern of the gasometer, terminates in the tar-vessel, fig. 2. Thus the vaporous fluids are condensed by passing through the serpentine pipe, E, E, &c. and become deposited in the tar-cistern, fig. 2; whilst the non-condensible or gazeous products are made to proceed by the pipe F, which branches off from the pipe E, into the lime machine, fig. 3. In this apparatus the gas, as it is evolved from the coals, comes into contact with slaked lime and water; the object of which is, to strip it of its sulphuretted hydrogen and carbonic acid gas with which it always abounds, and to render it fit for illumination. This being accomplished, the purified gas is conducted away out of the lime machine by means of the pipe G, into the perpendicular pipe H, which branches up through the bottom of the gasometer cistern. The upper extremity of this pipe is covered, in the manner of a hood, by a cylindrical vessel I, open at bottom, but partially immersed beneath the surface of the water contained in the outer cistern of the gasometer, it is also perforated round near the lower edge with a number of small holes. The gas, as it passes out of the pipe H, displaces the water from the receiver I, and escapes through the small holes, and is thus made to pass through the water in the cistern, in which the hood of the pipe I, is partly immersed, so as to expose a large surface to its action, that it may once more be washed, and deprived of all the foreign gazeous products which might have escaped the action of the lime, whilst it was agitated with this substance in the lime machine, fig. 3. After rising through the water in the gasometer cistern, it enters into the gasometer, which then ascends as the gas accumulates in it.

In this manner the process proceeds, until the whole of the volatile products of the coal in the retort are disengaged. The use of the gasometer is, partly to equalize the evolution of the gas which comes from the retort more quickly at some time than others. When this happens, the vessel rises up to receive it, and when the stream from the retort diminishes, the weight of the gasometer expels its contents, provided the main-cock be open. When the process is finished, the retort is suffered to cool, and its lid is then removed to replenish it with coal. When the main stop-cock is then opened, the gasometer descends, and the gas passes from the gasometer through the pipe K, to the burners, or main pipe, which communicates with the gas burners or lamps. L, is a wooden tub or barrel, containing the mixture of lime and water, for charging the lime machine; and into which the contents of the barrel, L, may be conveyed by the curved pipe M, without admitting common air. N, N, is a water-pipe, to convey fresh water into the gasometer cistern occasionally; because it is essential that the water used for washing and purifying the gas should be changed for fresh as soon as it becomes dirty; and unless this is done, the gas will not be perfectly purified by washing, but produce a disagreeable odour when burnt; the same holds good with regard to the lime machine, the contents of which should be renewed occasionally. This pipe also conveys the necessary water into the barrel, L. O, is a waste-pipe, to convey the water as it becomes impregnated with the impurities of the gas, out of the gasometer cistern. P, is an agitator, to stir up the contents of the lime machine occasionally, Q, Q, are two iron rods, which serve as stays to guide the motion of the gasometer. R, is an index, connected by means of a shaft and pulley with the axis of one of the gasometer wheels. This index is graduated to the capacity of the cubical contents of the gasometer, so as to indicate, by the rising and falling of the gasometer, its relative contents of gas expressed in cubic feet. S, is the waste pipe of the lime machine, to remove the insoluble parts of the lime. T, represents the iron cover, or lid, which is turned on the lathe, and ground air-tight, to close up the mouth of the retort, so as to make readily an air-tight fitting. U is an iron wedge to secure the cover of the retort. The left-hand retort in the design shows the retort closed up, and the cover, or lid of the mouth of it secured by means of the wedge, in its place, so as to render the mouth of the retort perfectly air tight.

There is a safety valve attached to this gasometer which could not be represented in the drawing; and the object of which is, to convey away any portion of gas that might happen to be produced by a careless operator, when the gasometer is full, and which is thus prevented from accumulating in the place where the gasometer is erected. It is represented in the right-hand corner of plate VII. where fig. 1 shows the edge of the gasometer; 2, the surface of the water in the inside of the gasometer; 3, the surface of the water in the outside of the gasometer, or in the cistern; 4, a pipe issuing from the lower edge of the gasometer, and surrounded at its upper extremity with a cup marked 5; 6, the waste pipe, the mouth of which is immersed in water. It is obvious that, when the gasometer is full, if an additional quantity of gas should be attempted to be put into it, it will be transported by means of the pipe 4, into the waste-pipe 6; the upper extremity of which reaches out of the building, and there communicates with the open air.

PLATE II.

Represents a Portable experimental Gas Apparatus for exhibiting, in the small way, the general nature of the gas-light illumination.—It is described page 79.

PLATES III. IV. V.

Show designs of various kinds of Gas Lamps, Chandeliers, Candelabras, &c.—See pages 114, 118, 140.

PLATE VI.

Fig. 1. Exhibits a design of the gasometer framing, or skeleton, which serves to give stability and strength to the gasometer. It consists of wooden frame work, marked A, A, A, interlaced with iron rods, B, B, B, &c. The whole framing is so disposed that it will float in the cistern horizontally, and therefore keep the gasometer perfectly steady and level with the surface of the water.

The rest of the sketches represent various kinds of gas pipes employed as mains for conveying the gas, and the methods of connecting them.

Fig. 2. Represents a longitudinal section of a Spigot and Faucet Pipe. These kinds of pipes are applicable in most cases as mains for conveying gas. A, is called the spigot, and B, the faucet. They are joined together, and made air tight, by iron cement, the composition of which is as follows:

Take two ounces of sal ammoniac, one ounce of flowers of sulphur, and sixteen ounces of cast iron filings or borings. Mix all well together, by rubbing them in a mortar, and keep the powder dry.

When the cement is wanted for use, take one part of the above powder, and twenty parts of clean iron borings or filings, and blend them intimately by grinding them in a mortar. Wet the compound with water, and when brought to a convenient consistence, apply it to the joints with a wooden or blunt iron spatula.

By a play of affinities, which those who are at all acquainted with chemistry will be at no loss to comprehend, a degree of action and re-action takes place among the ingredients, and between them and the iron surfaces, which at last causes the whole to unite as one mass. In fact, after a time, the mixture and the surfaces of the flanches become a species of pyrites (holding a very large proportion of iron,) all the parts of which cohere strongly together.

The inner parts of the faucet ought to be no larger in diameter than just to fit the spigot. This supports the pipe, independently of the cement, and prevents the risk of hurting the joint from any external stress. The inner faucet is commonly made about 2¹⁄₂ inches deep, and has the spigot inserted 1¹⁄₂ inch into it. The practice of some workmen, is to make the outer faucet, or that which contains the cement, six inches deep, for all pipes above six inches diameter; and to make the faucets of all pipes below six inches, the same depth as the diameter of the pipes. It is usual to make the space for the cement, all round the spigot, from 1 to 1¹⁄₂ inch; that width is required, in order that the cement may be firmly driven into the joint. When the space is very narrow, this cannot be done. On the other hand, when too wide, there is a waste of cement, and a risk of injury from unequal expansion.

Fig. 3. Exhibits a profile view of these kinds of pipes when joined together. The spigot and faucet pipes are liable to burst from the great expansion of the spigot, and the risk of this accident is increased by increasing the space between the spigot and faucet, which requires to be filled with cement.

Fig. 4. Represents a longitudinal section of two flanch pipes, and the modes of connecting them. A and B, show the parts of the pipes; and C and D, the flanches. These pipes are also joined together, and rendered air-tight, by interposing between the flanches rope-yarn, hemp, or some other pliable material, and iron cement, and then screwing up the faces of them by means of the bolts and screw nuts.

Fig. 5. Profile view of the same kind of pipes connected together, A and B, the pipes; C and D, the flanches; E and F, the bolts.

Fig. 6. Represents the method of joining spigot and faucet pipes when they are to have a turn or angle. This method is convenient when the place where the turn required to be made is previously known, and the pipes cast accordingly.

Fig. 7. Exhibits the method of connecting spigot and faucet pipes when they have a round turn. A and B, the junctures of the pipes.

Fig. 8. Represents a longitudinal section of the mode of joining pipes by means of what is called a thimble joint. The junctures of the pipes to be connected, are made air tight, as mentioned already, by iron cement. A, the thimble or small cylinder, with projecting edges, which unites the pipes B, C.

Fig. 9. A thimble joint made in two parts, which is sometimes convenient to join pipes. The parts are joined together by screw bolts, and nuts, in the usual manner.

Fig. 10. Section of the same.

Fig. 11. Represents a profile view of what is called the saddle joint. It is employed for taking off a branch-pipe. The branch has a piece A B, formed on its end, and fits round one-half of the outside of the pipe from which it is to proceed. C, is called the saddle, which fits round the other half of the pipe. The parts are secured together by screw bolts, and iron cement. By this method a branch may be formed on any part of a gas-pipe, by cutting a hole there, and applying the branch to that place. Where there is much risk of the inequality of expansion, the joints at certain places, should be secured by a soft stuffing of hemp and tallow; but in most cases the joints may be made with iron cement. Lead is frequently used for making the joints of gas pipes instead of iron cement, though cheaper and more easy of repair. The galvanic action which takes place between the lead and iron, soon renders the joints leaky, and the danger is increased by the unequal expansion of the two metals.

Fig. 12. Section of the saddle-joint.

Before the gas is suffered to enter into the pipe, they should be proved to be sound, by the usual process of forcing water into them: The pipes serving as mains, are placed perfectly solid, so that they cannot give way; their course should be rectilinear, having a descent of about 1 inch in 9 or 10 feet, to allow the water of condensation which may be deposited from the gas by a change of temperature to collect readily at the lowermost part.

Fig. 13. Shows a reservoir for collecting the water of condensation which might accumulate in the pipes. It consists of a receptacle, A, in which the water may pass; B, a branch-pipe closed at the top, by means of which the water may be removed, by drawing it out with a syringe. This receptacle is placed in those situations where pipes incline towards each other.

PLATE VII.

Exhibits a perpendicular section of a gas-light apparatus, calculated for lighting towns, or large districts of streets and houses.

Fig. 1. The Retort Furnace. The retorts are placed over each other in one or more rows; so that a certain number of them may be heated by separate fire-places. A, A, shows two of the retorts placed horizontally above each other; B, the fire-place; C, the flue which causes the fire to circulate round the retorts so as to heat them equally in every part; D, the opening of the flue where the fire passes into the chimney; E, the ash-pit; F, a chamber in front of the retort furnace, into which the orifice or mouth of the retorts project; G, G, the doors of the chamber, to enable the workmen to charge and discharge the retorts; H, a funnel shaped hole at the floor of the chamber F, through which the red hot coke as it is discharged from the retorts passes into the arched vault I; K, the syphon tube; L, the horizontal condenser[41]—the action of both of these pipes have been already explained, p. 168; M, main pipe, which conveys the liquid substances from the condenser, to the tar cistern, fig. 3, and which conducts also the gazeous products into the lime machine, fig. 2; N N, shows that part of the pipe which is interposed between the tar cistern, fig. 3, and the condensing pipe M,—it passes in a serpentine direction along the inner sides of the gasometer cistern, and, like the so-called worm in a distillatory apparatus, condenses the products which escape in a vaporous state from the condenser L; O, shows the place where the serpentine pipe N N, passes again out of the gasometer cistern, and its communication with the lime machine, fig. 2, and tar chamber, fig. 3. The action of the lime machine is as follows: The liquid products evolved from the coal, having been deposited in the tar cistern, fig. 3, by means of the serpentine pipe N, N, the gazeous products which accompany it, are conveyed by means of the pipe P, which branches out from the pipe O, into the interior receptacle of the lime machine marked Q, which consists of a vessel open at the bottom, and closed at the top, where it communicates with the pipe O. As the gas accumulates in the interior part Q, of the lime machine, it is made to pass through the liquid which it contains, namely, slaked lime and water; and escapes through appertures made in the horizontal partitions R, R, R, R, into the outer vessel, S, of the lime machine and from thence it is conducted away by the pipe T, T, T, into the additional washing apparatus, of the gasometer; fig. 4, the construction of this apparatus, greatly resembles the lime machine, fig. 2, namely, V, is a water pipe, proceeding from a cistern U, placed 3 or 4 feet above the orifice of the pipe V; T, T, is the gas-pipe, covered with a hood, marked W, and immersed in a small cistern, having horizontal perforated shelves, like those in the lime machine—they fit close to the hood. The gas which enters the hood W, meets with a shower of water delivered by the pipe V. The gas, as it passes through the holes in the horizontal partitions, is, therefore, again washed and thoroughly purified from foreign gases which may have escaped the action of the lime machine; Y, is a waste pipe, the lower extremity of which is sealed by being immersed in water,—it serves to carry away the water delivered by the pipe V, as it has been acted on by the gas. The summary action of this gas apparatus is, therefore, as follows: The liquid products obtained from the coal during the distillation are first deposited in the main condenser L, by means of the pipe K, and from whence they cannot escape until a quantity of tar has accumulated in it to a certain height, and by this means, one of the extremities of the pipes K, K, becomes immersed and hermetically sealed by the liquid which the condenser L, contains. The liquid products, after having accumulated to a certain height in the condenser, overflow the perpendicular portion which it contains, and discharge themselves into the pipe M, from whence they are transported into the tar cistern, fig. 3, by means of the system of pipes N, N, O, whilst the gazeous products are made to pass by means of the branch pipe P, into the lime machine, fig. 2. From this part of the apparatus the gas passes through the pipe T, T, T, into the additional or smaller washing apparatus placed upon a tressel in the cistern of the gasometer, where it is again exposed a second time to the action of a current of fresh water; and from this vessel the gas ascends into the gasometer. The gasometer is furnished with a pipe A, closed at the top, and fixed in one corner of the gasometer, but open at the bottom; it includes another pipe marked B, which communicates with the main pipe leading to the burners, or place where the gas is wanted. The pipe A, which slides over the pipe B, is perforated at the top, the gas passes through these perforations and is thus made to enter into the pipe B, and disposed of as mentioned. C, C, is a tube of safety adapted to the gasometer; its lower extremity remains sealed by the water in the cistern so long as the gasometer is not overcharged with gas; but, if more gas should be made to enter the gasometer than it is destined to receive, this pipe then delivers the gas into the funnel-shaped tube D, which reaches through the roof of the gasometer house, and thus the superfluous quantity of gas is conveyed away into the open air.

The cylindrical vessel P, of fig. 3, surrounding the orifice of the pipe O, which delivers the tar into the tar cistern, fig. 3, serves to keep this pipe constantly immersed into a portion of tar, so that the contents of the cistern may be drawn off by the cock without admitting air into any part of the apparatus. The tar cistern has a small hole at the top, to allow the air which it encloses to escape, as it becomes filled with tar and ammoniacal liquor. The main condenser L, is placed, as shown in the drawing, higher than the level of the water in the gasometer cistern, to allow a free descent of the distillatory liquids as they pass from this vessel along into the pipes M, N, O, &c. The cistern of the gasometer, as well as the lime machine, and tar cistern, are constructed of cast iron plates, bolted and cemented together with iron cement. The gasometer is made of sheet iron plates rivetted together—E, E, are two iron stays—G, G, are friction wheels.

METHOD of correcting the relative pressure of the Gasometer, so as to cause the gas which it contains to be uniformly of an equal density.[42]

We have mentioned already that the pressure of the gas in the gasometer should be invariable, for it is obvious that the weight of the gasometer is constantly increasing in proportion as it fills with gas, and rises out of the water—see p. 88, and 167. To render its pressure uniform, we first take the absolute weight of that part of the gasometer which becomes immersed in the water, and knowing the specific weight of the substance of which it is composed, we divide its absolute weight by the specific weight of the substance of which it is composed; and this being done, we make part of the chain, (measured at right angles from the axis of the wheels over which it passes downwards towards the top of the gasometer,) which is equal to the length of that part of the gasometer which becomes immersed in water, equal in weight to the specific gravity of the substance of which the gasometer is composed. For example, let us suppose that the part of the gasometer which becomes immersed in water weighs 861 lb. and that it is composed of sheet iron, the specific gravity of which, in round numbers, we will take to be 7. It is then evident, that the part of the chain of the gasometer measured downward from the axis of the wheel over which it passes, and which is equal in length to the height of the gasometer, must be loaded with a weight of, or must itself weigh, 123lb. for this would be the weight of the water displaced by the gasometer; or let us suppose the gasometer to be made of sheet copper, the specific weight of which (omitting decimals) is 8; and that the absolute weight of the gasometer is 1792lbs. then the chain of the gasometer equal in length to the height of the gasometer, immersed into the water must weigh 224lb. for this would be the weight of the quantity of water which the gasometer displaces. This being accomplished by then adding or diminishing the absolute or balance weight of the gasometer, any desired uniform pressure may be effected, and the same bulk of gas will always be of the same specific gravity.

DIRECTIONS TO WORKMEN ATTENDING THE GAS-LIGHT APPARATUS[43].

Particular care must be taken to make the joints of the mouth-pieces of the retorts perfectly air tight, which may be done in the following manner:—Take some common clay, dry, pulverize, and sift it, then add as much water as will make it into the consistency of treacle; make the mouth-piece and the lid of the retort clean, lay this luting thinly over the turned part of the lid, press the lid so luted gently to the mouth-piece, and then secure it moderately, by means of the iron wedge: if the workman observes this rule, he will never fail to make good joints; but if, on the other hand, the operator is careless and neglects to remove the old luting, &c. from the turned or smooth part of the mouth of the retort, and thereby cause a bad joint, the consequence will be the loss of a considerable quantity of gas, and a very disagreeable smell and smoke.

The bridge or row of bricks of the flue C, of the retorts, should never be made hotter than a bright red, which may be regulated by the door of the ash-pit being kept close shut when the fire is getting too hot. If the operator neglects this, and suffers the fire-bricks to arrive at a bright white heat the retorts will soon be destroyed, and bad gas be produced.

The gasometer should be well examined, at least once a week, to see if it leaks, by the following method, viz. Let the main stop-cock be shut, then make a mark on the gasometer at the water’s edge when it is full or nearly of gas, there being no gas coming from the retorts at the time, and if the mark sinks in the water, the gasometer leaks; to find out the place, walk slowly round it, and you may perceive the leak by the smell, apply a lighted candle to the part suspected, and if there be gas issuing from it, it will take fire, and perhaps appear like a small blue flame—blow it out, and mark the place: thus proceed round the gasometer till you have found all the places; if you perceive a smell, and yet cannot produce a flame in the part suspected, take a brush with a little thin white-lead paint, and lay it on the part where you think the leak is, and, if it be there, the gas which escapes from the leak, will immediately turn the paint brown. After the sides of the gasometer have been well examined, and secured by dipping a piece of cloth about the size of a shilling, into some melted pitch, tempered with a little bees-wax and tar, apply the cloth whilst hot to the place with the end of your finger, rubbing it till it is quite cold; next examine the top of the gasometer in the same manner,—when it is about two feet high in the cistern, it will then be better to get at. The water in the cistern should always be kept within 3 or four inches of the top, if suffered to sink much lower without replenishing, the gas will not pass through a sufficient quantity of water, and oily particles will be apt to condense in the pipes, to their great detriment.

The only thing to be observed in the place lighted is, that the lamps and pipes are not suffered to be touched on any pretence whatever, but by the person entrusted with their care. When a lamp is not wanted, it must be completely shut off from the pipe which supplies it, by a stop-cock provided for the purpose, and not opened again but when a flame is held over it; not a lighted candle, as the tallow is liable to drop into the lamps; lighted paper is better.

ESTIMATE OF THE PRICE OF A GAS-LIGHT APPARATUS, IF ERECTED IN LONDON,

Capable of affording, every 24 hours, Light equal to 40,000 Tallow Candles, six in the pound, burning one hour.

£. s.

Gasometer, to contain 10,000 cubic feet of gas 236 0

Wheel-work, regulating chain, ballance-weight for ditto, with wooden framing 160 11

Wrought iron cistern for gasometer—36 feet wide, 24 feet long and 16 feet deep 500 0

(It would weigh about 16 tons.)

Wooden framing built around it, to secure ditto 150 0

Condenser, cistern and communicating pipes 126 0

Lime machine, made of cast iron plates 82 0

Gasometer-house, built of frame-work and weather-boarded 250 0

Twenty-four retorts set in brick-work, with furnaces for ditto, compleat 336 0

Sundries 100 0

£ 1940 11

A gas-light apparatus complete for work, capable of affording every twenty-four hours a quantity of light equal to 1,400 Argand’s Lamps, each lamp equal in intensity to six candles, six in the pound, burning for five hours, will cost 3,500l. if erected in this metropolis.

LONDON Price List of the most essential articles[44] employed in the erection of a Gas-Light apparatus.

Sheet-iron pipes brazed.

s. d.

¹⁄₄ inch in diameter 0 4 a foot - in 15 to 18 feet lengths.

³⁄₈ ditto 0 4 ditto

¹⁄₂ ditto 0 5 ditto

⁵⁄₈ ditto 0 6 ditto

³⁄₄ ditto 0 6 ¹⁄₂ ditto

⁷⁄₈ ditto 7 ditto

1 inch, ditto 0 7 ¹⁄₂ ditto

1 ¹⁄₄ ditto 0 9 ditto

1 ¹⁄₂ ditto 0 10 ¹⁄₂ ditto

1 ³⁄₄ ditto 0 11 ditto

2 inch, ditto 1 1 ¹⁄₂ ditto

2 ¹⁄₄ ditto 1 4 ditto

2 ¹⁄₂ ditto 1 5 ditto

3 inch, ditto 1 6 ¹⁄₂ ditto

Copper pipes brazed ¹⁄₄ inch 0 4 per foot

Ditto, ditto, ditto ³⁄₈ inch 0 5 ¹⁄₂ ditto

Gas-light cockspur burners with stop-cock 2s 6d to 3s 6d

Argand’s lamps, with glass-holders, from 3s to 4s 6d

Cast-iron retorts, weighing 7 cwt. at 15s 6d per cwt £5 8 6

Mouth-piece for ditto, compleat 1 14 8

Cast-iron door frames for retort furnace 1 0 0

Furnace bars 10s. per cwt.

Sheet iron for gazometer (No. 23) 24s. per cwt.

Gazometer chains, 5d per lb.

Ballance weights [Plates] for gazometer, 9l 10s per ton.

Cast-iron cistern plates

----------------------- smaller size for lime machine, 18l per ton.

----------------------- middling size for tar cistern, 16l ditto

----------------------- largest size for gazometer cistern 14l ditto

Cast-iron flanch pipes 2 - inch diameter, at 5s per yd. in 6 feet lengths

ditto 3 ditto 6s ditto 6 ditto

ditto 4 ditto 8s 6d ditto 9 ditto

ditto 5 ditto 10s ditto 9 ditto

ditto 6 ditto 12s ditto 9 ditto

ditto 7 ditto 13s 6d ditto 9 ditto

ditto 8 - 11l. 5s. per ton 9 ditto

ditto 9

ditto 10

ditto 11

¹⁄₂ inch nuts, screws and washers to put iron pipes together 7d. per lb

⁵⁄₈ ditto 7d. ditto

³⁄₄ ditto 6d. ditto

English bar-iron 13l. per ton

Best, ditto 18l. ditto

FINIS.

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