IT is comparatively easy to get rid of smoke, if the consumption of fuel and production of steam be disregarded. A few perforations in the door or bridge will attain the object; but the effect of this continuous admission of air above the fuel will be to diminish the supply of steam from twenty-five to thirty per cent, as many can testify to their cost.
The superiority of Mr. Prideaux's invention consists in this; that it only admits a full supply of air immediately after coaling; lessens the supply as less is required from the fuel becoming coked; and, finally shuts it off altogether, when, from this operation being complete, no more is desirable; burning in fact all the smoke by the admission, on the average, of only one-fifth part the quantity of air above the fuel, which would enter on the principle of continuous supply.
Another feature of this invention worthy of notice is the coolness (we may say, without exaggeration, coldness), of the furnace-door. During the time of the action of the valve, the face of the door is reduced to the temperature of the entering stream of air; and it rarely rises above this in the intervals when it is closed, so extraordinary is the effect of the peculiar arrangement of plates in the interior (presenting a surface of 8000 square inches) in arresting the passage of heat.
A large body of evidence leads to the conclusion that the saving is never less than 10 per cent in Cornish boilers, and 15 per cent in brick furnaces; on which supposition it is clear that, irrespective of the question of smoke, the adoption of the invention becomes a matter of economy.
In no case, however, does the introduction of this invention offer such great advantages as in that of steam-vessels, from the confined character of the stoke-hole. Mr. Fairbairn, at a recent meeting of the Institute of Mechanical Engineers, after remarking " that it would, doubtless, be an advantageous addition to any boiler, however well constructed for burning the smoke, by making the process more complete and certain in its effects," proceeded to observed, " that the apparatus appeared particularly applicable to marine boilers, where the heat of the, stoke-hole was ordinarily very objectionable, and interfered seriously with the duties of the men; and he was surprised it had not been taken up by the marine authorities on that account, as well as for effecting the consumption of smoke. Those valves that he had seen at worn certainly kept quite cool and in very complete order, and had not been injured at all by the heat."
The invention is already introduced on the Tyne, the Clyde, and the Mersey, and, by this time, in all probability, in the Danish navy In short, the invention of Mr. Prideaux bids fair to become as uniform an appendage to the furnace as the generator is to the steam-engine.
There was some dispute over the Prideaux machine door and valve's viability in real use. The book The Combustion of Coal and the Prevention of Smoke argues that the furnace need a gradually increasing amount of air after a recharge of coal not a gradually decreasing supply etc.
Sources: The New York Journal 1856, The Combustion of Coal and the Prevention of Smoke:...by Charles Wye Williams 1854