It remains further to be observed that the coal, by yielding gas and other products, namely, tar, pitch, and ammoniacal liquor, is not entirely lost. It produces, besides light, an excellent fuel, namely, coke; and as a manufactory, or workshop, generally requires heating as well as lighting, there is a gain both ways. The manufacturer, by distilling his coal instead of burning it as it comes from the pit, saves his candles and improves his fuel. One effort at the outset in erecting a gas apparatus, will reduce his annual disbursement for those two articles of prime necessity, much in the same manner, though in a greater degree, as the farmer gains by building a thrashing machine and laying aside the use of the flail.
The coal is so far from being reduced in consequence of the gas-light process, to an useless mass, that in many places immense quantities are reduced to the state of coke for the purpose of rendering the coal a better fuel than it was in its natural state; for coke gives a strong and lasting heat. It is equally valuable for kitchen and parlour fires, and still more as a necessary requisite in some important branches of manufacture, so that in whatever quantity coke may be produced, it can never want a good market. The demand for coke in this capital, since the establishment of the gas-light works, has prodigiously increased. Numerous taverns, offices, and public establishments, which heretofore burnt coal, now use coke to the total exclusion of coal; and in almost every manufactory, which requires both extensive lighting and heating, gas and coke are now the means jointly employed. A coke fire emits a very uniform and intense heat; it produces no sparks, and burns free from soot and smoke; it requires no trouble in managing, and to those who have the misfortune of being plagued with a smoaky chimney, affords the only certain cure.
Another valuable product is the tar which is deposited during the production of the gas, this tar when rectified by a slight evaporation, has become an article of commerce. Large establishments, both of coal tar, coal oil, and pitch, are in full action, and the commodities which they furnish have become in great demand. The ammoniacal liquor which the gas-light process affords, has of late given rise to very important branches of chemical manufacture, carried on upon a large scale. But as the gas is at present supposed to be the only object in view, for the sake of the light which it yields, the other products being only accidentally connected with its extraction, let us leave the idea of profit on them out of the question, and with the utmost latitude of concession, require them only to stand as in part for a portion of the coal employed in the process, we have still the gas, an article which performs the functions of the oil, the tallow, or the wax for which it is substituted; and to the price of which we have no need to call the attention of those who make use of them. There remains only to be opposed on the other side, the expence of the apparatus by which the gas is to be prepared, and the lights maintained. From the materials and the workmanship, with the interest of the capital sunk, the expence in the first instance, must be very considerable. But where the quantity of light must be great, even from cheap substances, or where, with a less quantity of light, the substances from which it is derived must be of the costliest kind; such is in either case the enormous expence of these materials, that by superseding them and making every reasonable allowance to the engineer who erects the gas apparatus, the sum it costs, both principal and interest, is soon liquidated, leaving at last a total saving, excepting the expence of accidental repairs, which, from the durability of the materials employed, seldom exceeds a trifling sum.
The principal expence in the pursuit of this new branch of civil and domestic economy, is therefore, the dead capital employed in erecting the machinery for obtaining and conveying the gas. The floating capital, after the first cost incurred in erecting the apparatus, is comparatively small; even if usurious interest is allowed for the first cost of the apparatus, and its deterioration, the saving must always be considerable, especially if the number of lights furnished are comparatively in a small place.
At the same time were we to offer 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 forty pounds. But when a street, or small neighbourhood is required to be lighted the operation may be commenced with safety; the sum required for erecting the apparatus, and the labour attending the process, together with the interest of money sunk, will then soon be liquidated by the light and other products.
Individuals have accordingly engaged successfully in the distillation of coal, and trade with advantage in the articles produced by the process.
In like manner may the lighting of cities 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.
The supplying of light to the street or parish lamps alone, of any district of street lamps only, can never be undertaken with economy in this capital, nor indeed in any other; for the money sunk in furnishing the mains or pipes only, must always greatly exceed what any revenue from the lighting of the streets alone can compensate.
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 profit of this mode of illumination is the least. Hence, the lighting of the parish, or street-lamps alone, without lighting shops or houses, can never be done with economy.
It may be objected to the universality of our conclusion that the price of coal differing very much in different places will occasion a variation in the expence of the new mode of lighting.