54 ANNUAL OF SCIENTIFIC DISCOVERY. 



founded on the observation, that, during wet weather, the rain as it descends 

 carries with it the sooty particles of the smoke ejected by chimneys, the 

 humidity of the atmosphere causing the particles to cohere, and ultimately to 

 fall, partly by their own weight, and partly by their imbibing a portion of 

 the water with which the air is impregnated. The farther the body of smoke 

 recedes from the chimney, the more it becomes cleared, or washed, of these 

 particles. 



He proposes to eifect this cleansing process by means of the same 

 agent, namely, water, before the smoke shall ascend the chimney ; and the 

 modus operandi is as follows : To introduce into the main flue behind the 

 boiler, where such an arrangement exists, or at a convenient height in the 

 chimney stalk, where no such flue is used, a jet of water, say the spare 

 water hot from the engine. This jet to be allowed to fall upon the blades of 

 a fan made to revolve rapidly and break the water completely into a fine 

 spray or dense mist, filling entirely for yards in length, or height, as the 

 case may require the chamber through which the smoke must pass as it 

 rushes from the furnace. By this process of washing, every particle of soot 

 would imbibe moisture sufficient to cause it to descend to the bottom, and 

 there be carried off by a small aperture. Others of the component parts of 

 the smoke would undergo a chemical change by its passage through the 

 broken water, which would hold them in suspension or solution, and carry 

 them off by the drain. The objection which would naturally be started, on 

 a superficial glance at the proposal, that the introduction of such machinery 

 into the flue or chimney would lessen the draught and impede the progress 

 of the smoke, might be met by the fact that the water introduced, being hot, 

 would not lower the temperature, while the motion of the fan, the blades of 

 which should be formed on the principle of the screw propeller, with the 

 front of the screw turned in the direction of the furnace, would really accele- 

 rate rather than retard the draught. The jet of water coming in contact 

 again and again with the blades of the screw would also, by this form of fan, 

 be reduced to a spray of the requisite consistency. 



An apparatus for the consumption of smoke, patented by Mr. Woodcock, 

 of London, consists in the admission of heated air, to promote combustion, 

 at a point where an inverted bridge forces the unconsumed smoke dow,n upon 

 the red fire. The smoke is thus brought into contact with the fire, and sup- 

 plied with the requisite amount of oxygen, in a heated state, to facilitate its 

 combustion. The precise arrangement varies with the length of the boiler 

 and other circumstances, sometimes an extra inverted bridge, iron plate af- 

 fixed to the top of the flue, being attached. The heated air is introduced 

 through a sort of hollow bridge, the front of which is of brick, and the back 

 of perforated plate iron. The supply reaches it either under the furnace, in 

 the ordinary way, or through a tube on cither side of the furnace. 



In some experiments recently made at Manchester, England, with this ap- 

 paratus, the steam in the boiler was allowed to subside considerably below 

 the ordinary pressure, in order that the fires might be supplied with coal more 

 freely, and also to show whether, and in what proportion, an increase of 

 steam could be generated. When the steam was reduced to thirty pounds 



