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.
[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 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.