coal would yield 24 quarts. Soot then consists chiefly of unburnt charcoal.

Take out of the fire, a piece of charcoal about an inch or half an inch long, well lighted at one end. You may hold it in your fingers, and even excite by blowing, the lighted end, without being burnt. Charcoal therefore is a very bad conductor of heat. Take a piece of iron or brass, a foot long, and holding it at one end, thrust the other into the fire. Long before it approaches a red heat, your fingers will be burnt. Metals therefore are very good conductors of heat. Hence, when we suffer soot to accumu. late at the bottom of our boilers, we exchange a very good for a very bad conductor of heat; and we must employ more fuel, for the purpose of communicating the same heat to the water. Hence it is a point of economy to consume the smoke under the boiler of a steam engine.

The method of consuming the smoke of furnaces, depends upon two principles: 1st. the vivid, well-lighted coals, are pushed forward, and the half lighted coals are not thrown upon or beyond them promiscuously, but placed at that part of the fire, where the body of vivid coals commences: hence the smoke arising from the half-lighted, can be made to pass over the lighted coals. But the smoke would rise up, if it were not, 2ly. that a current of air is admitted, and directed downward, so as to drive the rising smoke upon and over the surface of the red hot coals, where it is burnt and consumed as fuel.

Suppose the door frame of the fire place, shuts against a platform, not level with the fire as usually is the case, but raised above the burning fuel, &c. slanting downward from the inside of the door toward the fire; so that the coals can be easily pushed inward to any part of the fire ; if then, there be a slit of an inch wide for instance, across the door, a current of air will pass through that slit over the fire in addition to the current of air that passes upwards

through the bars and among the fuel. By means of a piece of sheet iron placed slanting over the slit withinside, this current of air through the slit in the door, can be directed so as to drive the smoke of the fresh coals, down upon the burning coals, and there it will be consumed.

The three following methods, which can be well under stood from the plates, have long been in use in England, and therefore can be employed for the purpose of consuming smoke as well here as there.

In the year 1791, the steam engines on Watt's construction at Manchester, consumed the smoke: the public complained that no method was adopted by the owners of other steam engines, and by the dyers in and near that town, to produce the same effect in their furnacefires. I applied to Boulton and Watt, and obtained permission for any person to use their patent in this respect, whether connected with one of their engines or not. Of course the smoke of the furnaces was consumed gene. rally, on paying a moderate premium for the use of the invention.

Several furnaces however were erected from time to time, and steam engines already put up previous to the improvements of Boulton and Watt, were worked with furnaces, which were not built on a construction necessary to consume the smoke. In the Monthly Magazine for 1796, the reader will find an account of six owners of steam engines and furnaces at Manchester, who were indicted at the quarter sessions for a nuisance, inasmuch as they did not use means to consume the smoke of their furnaces they were convicted, and fined one hundred pounds sterling each; and the conviction was acquiesced in. I have no hesitation in saying that the neglect of employing such means, is just as much a nuisance in this country as in that. I now publish in a manner not to be mistaken, the methods of producing this effect; one or

other of which is in common use in Great-Britain, and either of which will answer the purpose. A steam engine of the power of a dozen horses, need not, and ought not, to send forth so much smoke as a common sitting room fire: the method of producing this effect, is not a tax upon the owner, but an advantage; for he consumes his fuel more perfectly, and none goes to waste. If steam engines continue to be erected in large towns, without having this improvement attached to them, instead of being as they might be, blessings to the neighbourhood, they will make our towns uninhabitable; and I would earnestly recommend that the legal question of nuisance should be settled, by an indictment brought against the offenders.

Specification of the Patent granted to Mr. JAMES WATT, of Birmingham, in the County of Warwick, Engineer; for certain newly-improved Methods of constructing Furnaces or Fire-places, for heating, boiling, or evaporating of water, and other Liquids; which are applicable to steam-engines and other purposes; and also for heating, melting, and smelting, of Metals, and their Ores; whereby greater effects are produced from the Fuel, and the smoke is in a great measure prevented, or consumed.

Dated, June 14, 1785.

TO all to whom these presents shall come, &c. Now KNOW YE, that, in compliance with the said proviso, and in pursuance of the said statute, I the said James Watt, do hereby declare, that the following is a particular description of the nature of my said invention, and in what manner the same is to be performed; that is to say, my said newly-improved methods of constructing furnaces or fire-places consist in causing the smoke or flame of the

fresh fuel, in its way to the flues or chimney, to pass, together with a current of fresh air, through, over, or among, fuel which has already ceased to smoke, or which is converted into cokes, charcoal, or cinders, and which is intensely hot; by which means the smoke and grosser parts of the flame, by coming into close contact with, or by being brought near unto, the said intensely hot fuel, and by being mixed with the current of fresh or unburnt air, are consumed, or converted into heat, or into pure flame free from smoke. I put this in practice, first, by stopping up every avenue or passage to the chimney or flues, except such as are left in the interstices of the fuel, by placing the fresh fuel above, or nearer to, the external air than that which is already converted into cokes or charcoal; and by constructing the fire-places in such manner that the flame, and the air which animates the fire, must pass downwards, or laterally, or horizontally, through the burning fuel, and pass from the lower part, or internal end or side, of the fire-place, to the flues or chimney. In some cases, after the flame has past through the burning fuel, I cause it to pass through a very hot funnel, flue, or oven, before it comes to the bottom of the boiler, or to the part of the furnace where it is proposed to melt metal, or perform other office, by which means the smoke is still more effectually consumed. In other cases, I cause the flame to pass immediately from the fire-place into the space under a boiler, or into the bed of a melting or other furnace. The drawing Figure 1 (Plate I.) shews a section of a fireengine boiler, and its furnace or fire-place, which I have chosen for an example of the application of this new method to the heating and evaporating of water. AA is the boiler, which may be made of any form suitable to its use. BB is a flue, surrounding the boiler as usual. Cis the uptake, or passage from the space under the boiler to the flues. DD is a funnel or flue for the flame to

come from the fire-place to the boiler. EE is a place to contain the ashes; and F is a door to take them out at, which must be kept continually shut during the time of working. G H is the fire-place: the fresh fuel is put in at G, and gradually comes down as the fuel below consumes. The part at H is very hot, being filled with the cokes or coals which have ceased to smoke. I is an opening or openings, to admit fresh air, and regulate the fire. K is a door into the space under the boiler; which, being opened, admits air, and stops the draught of the chimney when the operation is wanted to cease. Figure the second is a section of the same fire-place in the other direction; in which M M is the back of the fireplace; L the brick arch on which the fuel lies; and E the ash-hole. Figure 3 is an outside view of the same fire-place, shewing the air-holes I I, and the ash-hole door F; and Figure 4 is a plan of the same, with part of the boiler seating, taken in the line Z Z of Figure 1. The dotted lines represent the flues, and the darts point out the direction of the flame. The fire is first kindled upon the brick arch L, (Fig 1.) and when well lighted, more fuel is gradually added until it is filled up to G; and care is taken to leave proper interstices for the air to pass, either among the fuel, or between the fuel and the front wall N; and as much air is admitted at II as can be done without causing the smoke to ascend perpendicularly from G, which it will do if too much air is admitted at II. The dimensions of this fire-place are shewn by the scale, and are properly adjusted for burning about eighty-four pounds weight of coals in an hour; where greater or less quantities are required to be burnt, the furnaces must be enlarged or diminished accordingly; or, if much greater, more furnaces than one must be employed. Figure the fifth represents this new fire-place as applied to a furnace for melting iron and other metals, and constructVol. II.

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