180 General Description.
the troke alone performs the united function ofcylinder, piston, beam, crank, and fly-wheel; thusensuring a decided superiority over the recipro-cating engine.
• The advantages resulting from the use of steamengines have, in some cases, been considered asfully equipoised by the smoke and noxious effluviawhich proceed from their capacious vomitories;and this, in large manufacturing towns, is indeedan evil of some importance, to obviate which avariety of contrivances have been suggested.
The first attempt at consuming smoke, appearsto have been made by M. Dalesme, a French en-gineer, who exhibited a contrivance of this de-scription at the Fair of St. Germain’s in 1685.* In1785 Mr. Watt obtained a patent for the construc-tion of an economical furnace, which not only con-sumed the smoke, but employed it as an usefulauxiliary in increasing the heat. To understandthis it will be necessary to observe, that the densesmoke which is usually discharged at the top ofthe chimney, is in fact, so much good fuel, whichrequires but a sufficient supply of oxygen to renderit fit for combustion.
Mr. Watt accomplished this in his early enginesby stopping up every avenue to the chimney, ex-cept such as might be left in the interstices of theignited fuel, and the smoke from the fresh coal was