The nuisance occasioned by the smoke of coal-fires has formed it subject of complaint from the earliest times in which mineral fuel was extensively used; and tho great increase of steam-engine and other furnaces, consequent on the extension of manufactures, has afforded, of late years, additional ground for attempts to abate the nuisance. Such attempts are important, not only for the purification of the air, but also for the economy of fuel ; since the matter which gives smoke objectionable density and colour is uncousumed fuel in a finely-divided state. It appears, therefore, that if a supply of air could be thrown Into a fire in such a way, as to occasion the combustion of the carbona ceous matter, the result would be that a greater amount of heat would be obtained from a given quantity of fuel, at the same time that the nuisance of smoke would be abated. It may be observed, that the quantity of smoke emitted from furnace-chimneys varies much with the state of the fire, being greatest when a mass of fresh fuel is thrown on, and least when the fire has burned clear or the fuel is fully ignited. Attention to this circumstance, on the part of the stoker, will greatly diminish the nuisance ; because, if he throw on the fresh fuel in a thin layer, it will the sooner become perfectly ignited ; and, by laying it in the fore part of the furnace, the dense smoke arising from it has to pass over that part of the fire which is in a state of more perfect com bustion, and is thereby in a great measure consumed. Many of the contrivances introduced or suggested as smoke-consuming furnaces act on these principles ; arrangements being adopted to insure the right feeding of the fire without much attention on the part of the firemen.
James Watt was one of the first to obtain a patent for a smoke consuming or smoke-preventing apparatus. He caused the smoke of the fresh fuel, in its way to the chimney, to pass, together with a current of fresh air, over fuel which had already ceased to smoke, and was intensely hot ; by which means the smoke, by coming into close contact with the hot fuel, and being mixed with the current of fresh air, was converted into pure flame, free from smoke. Since that time innumerable plans have been brought forward for intro ducing the necessary supply of air to the furnace ; but while many of them accomplish the purification of the smoke as completely as could be desired, many others increase the consumption of fuel or weaken the draught of the furnace. If the air admitted to the furnace be cold, it diminishes the heat of the fire; and if hot, expense is incurred in heating it, whether this be effected by a separate fire or by passing the air in pipes through the chimney. Most railway com panies are required, by their acts of incorporation, to avoid the emission of smoke from their engines; and this is usually done, at great expense, by the use of coke. To lessen this expense, Mr. Chanter devised a plan, consisting in the introduction of a deflector dipping into the burning fuel, which compels the smoke from the crude coal to pass through a mass of burning coke, supplied through a email door, and conducted at once to the back of the furnace. By this means three parts of coal may be used to one of coke, with very little risk of much smoke.
Another mode of destroying smoke is by injecting steam into the furnace. The plan has been tried by several inventors, among others by Mr. Iveson. In his apparatus, the steam is thrown into the fire in several minute jets, from a fan-shaped distributor in the fore part of the furnace. The steam not only destroys the smoke, but also greatly increases the intensity of the fire. Thus the necessity for a large chimney is obviated, it being only necessary to provide a small passage for the escape of the gaseous products of combustion. Experiments on the same furnace, with and without the injection of steam, indicate a saving of fuel to the amount of 33 per cent.; the consumption in five hours being respectively 558 and 812 the. As a drawback from this saving, the plan requires, in a steam-engine furnace, about one tenth of the steam generated, and in other furnaces renders necessary the erection of a small boiler. It is proposed, in high-pressure engines, to make use of the waste steam for the purpose of injection.
Besides the numerous plans for the combustion of smoke, various methods have been tried on a limited scale for conducting it to a dis tance from the buildings in which it is formed, by means of subterra neous channels; and for condensing it by means of a shower of water, so that the sooty matter might be conveyed away by the sewers.
In 1819, a committee of the House of Commons was appointed " to inquire how far it may be practicable to compel persons who use steam-engines and furnaces in their different works to erect them in a manner less prejudicial to public health and comfort." The committee,
iu their Report, noticed, among other plans, that of Mr. Steel, in which the fuel was supplied in a constant stream, by means of an inclined hopper ; the quantity of coal supplied in a given time, and the size of the pieces, being regulated by a grooved roller. The fuel was distri buted over the bed of the furnace by the motion of the grate itself, which was of a circular form, and turned on a central pivot. Tho committee, after much investigation, reported that efficient means for destroying smoke had been "satisfactorily and effectually obtained." An act of parliament was passed to enforce the use of smoke-consuming apparatus ; but it was very little attended to, and the smoky condition of our great towns increased quite as rapidly as the increase of popu lation and manufactures. After many years had passed, the Commons appointed another committee of inquiry in 1843. This committee examined a large number of scientific and practical men, among whom were Dr. Faraday, Dr. Arnott, Professor Brandt), Dr. Ure, Admiral Parry, Dr. Reid, Mr. Jukes, Mr. Solly, Mr. Muntz, and Mr. I louldsworth. Nearly all concurred in opinion that smoke may be nearly prevented, either by existing methods or by apparatus easy to devise. Voluntary associations had been formed in many largo manufacturing towns, including Leeds, Bradford, and Manchester, to put down the nuisance. In numerous factories there was a positive saving of fuel effected by the avoidance of smoke ; but most of the manufacturers declared that the apparatus hitherto employed had not fulfilled the promises made. The committee recommended an act of parliament, but none was passed at that time. In 184 I, before the Health of Towns Commission, Mr. Thee. Cnbitt (than whom few men were more thoroughly versed in the philo sophy of house-building) advocated smoke-prevention very energeti cally, as being practically attainable, morally obligatory, and financially profitable. Another committee sat in 1845, followed by an attempt to pass a smoke-prevention act ; but this was frustrated by certain influential manufacturers, who did not like the trouble attending the adoption of new apparatus. When the Health of Towns' Act was passed, clauses were introduced which empowered town-councils to attack the smoke nuisance in their own way, and within the limits of their own towns ; and many places availed themselves of this power. After other minor attempts at legislation, acts were passed in 1853, 1856, and 1857, rendering it compulsory to adopt smoke-preventing contrivances. Two of these acts related to the metropolis and one to Scotland. Certain trades were exempted from the operation of the statutes, and certain dates were named on which the penalties for non observance would begin to be enforced. Not only furnaces employed in trades and manufactures, but also steam-boats working above London Bridge, were brought within the scope of the acts relating to the metro polis. The police received certain powers in relation to this matter, and the provisions of the acts were sought`to be enforced by penalties.
Improvements have resulted from these legislative enactments ; but the evil is still far from being removed. There seem to be difficulties attending the enforcement of the law. Those manufacturers, whose furnaces are arranged on the old plan, protest against the expense necessary for adapting the smoke-preventing apparatus ; and they are not slow to declare that the several inventions fail in some or other of the requisite conditions. On the other hand, the statements are most clear and positive that the evil can be prevented, and that a saving iu fuel rewards those who resolutely make the attempt. Printers, woollen spinners, builders, metal-founders, button-makers, sugar-refiners, steam corn-millers, porter brewers—all have placed upon record the declara tion that gain as well as cleanliness results from the adoption of smoke-preventing apparatus.
We shall make no attempt to describe the numerous forms of appa ratus patented within the last few years. All of them belong to one or other of two classes. They attempt either smoke-consumption, by supplying the heated smoke, at a particular spot, with fresh air enough to kindle and consume it ; or smoke-prevention, by so supplying fuel that it may ignite without forming smoke at all. Jukes' apparatus belongs to the latter class.
The inventions of Dr. Arnott would call for some attention here, were it not for the fact that his ingenious stoves and ventilating appa ratus had better be described under WARMING AND VENTILATION, in connection with many other kinds of apparatus for similar purposes.