HOTHOUSE FURNACES. 



255 



was also consumed. And a simple but 

 highly ingenious grate, in which the burn- 

 ing fuel was made to consume its own 

 smoke, was one of the many original 

 contrivances of Dr Franklin. Soot is 

 very inflammable ; and when we reflect 

 that one pound weight of it gives as much, 

 if not more heat, than a pound of coal, 

 we need not be surprised at the increas- 

 ing anxiety for the construction of fire- 

 flues and furnaces that will consume their 

 own smoke. 



One of the simplest and most success- 

 ful appears to be one mentioned in a 

 report to the " Liverpool Health of Towns 

 Advocate," the invention of Mr Wye 

 Williams, and kindly furnished to us by 

 John Sutherland, Esq., M.D., of that 

 town. " It consists in placing a per- 

 forated iron plate, several feet square," 

 but of course proportioned to the size of 

 the furnace, " immediately behind the 

 fire-bridge in the bed of the flue. The 

 air is admitted into a space below this 

 plate, and is diffused by passing through 

 the apertures. The gases and carbona- 

 ceous vapours become immediately 

 ignited when the air is admitted, and no 

 smoke is produced. The annexed sketch, 

 fig. 341, will show the plan : a the boiler, 



Fig. 341. 



d 



b the fire-place, c the flue, d the chimney, 

 e the ash-pit, / the fire-bridge, g the 

 diffusion- plate, through which the air 

 passes before it plays upon the hot gases ; 

 h a space into which the air is intro- 

 duced from without, the quantity being 

 regulated by a valve. This plan requires 

 no other management than to keep the 

 fire-bars always covered with fuel ; and 

 the size of the diffusion-plate must be 

 ascertained by trial, and also the quantity 

 of air to be admitted. Of course this 

 should be no more than sufficient to 



effect the combustion, otherwise the 

 boiler is cooled down." Mr Joseph 

 Williams of Liverpool has effected an 

 important improvement on this plan, by 

 introducing hot-air into the space h, by 

 making it pass through hollow bars or 

 tubes placed near the fire, instead of 

 admitting it directly from the atmosphere. 

 The waste in fuel alone in furnaces where 

 the smoke is not consumed is enormous — 

 amounting to nearly one-third of all the 

 coal used. The experiments of Mr Henry 

 Holdsworth of Manchester have shown 

 that, in the front flue of a furnace of 

 common construction, the thermometer 

 seldom rose above 1100°, and often fell 

 below 900°, the mean being 975° ; while 

 in the same furnace, while consuming its 

 smoke, the mean temperature was 1160°, 

 ranging between 1400° and 1000°. The 

 quantity of water evaporated by a pound 

 of coal was one-half greater than when 

 the smoke was not consumed. 



The perfect combustion of coal in a 

 furnace fire requires that the gases gene- 

 rated during the process of burning should 

 be brought in contact with an adequate 

 supply of fresh air, so as to furnish oxy- 

 gen for the conversion of the whole of 

 the carbon into carbonic acid gas, which 

 is invisible. If from any cause the sup- 

 ply of air be inadequate to effect this 

 object, the carbon is disposed of in the 

 form of smoke ; and every atom thrown 

 in this state into the atmosphere is not 

 only a source of nuisance, but is also the 

 cause of a direct pecuniary loss to the 

 proprietor of the furnace. 



Witty' s or Chanters smoke-consuming fur- 

 nace, of which the annexed fig. 342 is a 

 sketch, has been hitherto more extensively 

 used in gardens than any other ; and, 

 when proper attention is paid to its work- 

 ing, it answers extremely well. Exclusion 



Fig. 342. 



of air, excepting when made to pass di- 

 rectly through the fire from the ash-pit, is 



