THE "VOSHUXPTWN OF -SMOKE." 329 



Therefore, when the coal gas and the air are brought to> 

 getlier oneja the other, or both, must be heated up to a 

 certain point in order that the combustion be complete. If 

 cold there is no combustion; if insufficiently heated, there 

 is imperfect combustion, however well the supplies may be 

 regulated. 



A very simple experiment that anybody may make illus- 

 trates this. When an ordinary open fire is burning brightly 

 and clearly without flame, throw a few small pieces of raw 

 coal into the midst of the glowing coals. They will flame 

 fiercely, but without smoking. Then throw a heap of coal 

 or one large lump on a similar fire. Now you will have 

 dense volumes of smoke, and little or no flame, simply be- 

 cause the cooling action of the large bulk of coal in the 

 course of distillation brings the temperature of its gases 

 below that required for their complete combustion. 



This simple experiment supplies a most important prac- 

 tical lesson, as well as a philosophical example. The best 

 of all smoke-abatement machines is an intelligent and con- 

 scientious stoker, and every contrivance for smoke abate- 

 ment must, in order to be efficient, either be fed by such a 

 stoker or provided with some automatic arrangement by 

 which the apparatus itself does the work of such a stoker 

 by supplying the fresh fuel just when and where it is 

 wanted. 



Cornish experience is very instructive in this respect. 

 The engines that pump the water from the mines do a 

 definitely measurable amount of work, and are made to 

 register this. The stoker is a skilled workman, and prizes 

 are given to thoso who obtain the largest amount of ." duty" 

 from given engines per ton of coal consumed. Instead of 

 pitching his coal in anyhow, cramming his fire-hole, and 

 then sitting down to sleep or smoke in company with his 

 chimney, the Cornish, or other good fireman, feeds little 

 and often, and deftly sprinkles the contents of his shovel 

 just where the fire is the brightest and the hottest, and 

 the bars are the least thickly covered. The result is re- 

 markable. A colliery proprietor of South Staffordshire 

 was visiting Cornwall, and went with friend to see his 

 works. On approaching the engine-house and seeing a 



