obtained in the Combustion of Fuel. 349 



effect in a satisfactory manner, and in accounting for it 

 we shall explain a circumstance on which it is probable 

 that the great increase of the heat of an open fire where 

 these balls are used may in some measure depend. 

 The small particles of coal and of cinder which in a 

 common fire fall through the bottom of the grate and 

 escape combustion, when these balls are used can hardly 

 fail to fall and lodge on some of them ; and as they 

 are intensely hot, these small bodies which alight upon 

 them in their fall are soon heated red-hot, and disposed 

 to take fire and burn ; and as fresh air from below the 

 grate is continually making its way upwards amongst 

 the balls, every circumstance is highly favourable to the 

 rapid and complete combustion of these small inflam- 

 mable bodies. But if these small pieces of coal and 

 cinder should, in their fall, happen to alight upon the 

 metallic bars which form the bottom of the grate, as 

 these bars are conductors of heat, and, on account of 

 that circumstance, as well as of their situation, below 

 the fire, never can be made very hot, any small 

 particle of fuel that happens to come into contact with 

 them not only cannot take fire, but would cease to burn, 

 should it arrive in a state of actual combustion. 



These facts are very important, and well deserving of 

 the attention of those who may derive advantage from 

 the improvement of fireplaces and the economy of fuel. 



There are some circumstances w.hich strongly indicate 

 that an admixture of incombustible bodies with fuel, 

 and especially with coal, causes an increase of the heat, 

 even when the fuel is burned in a closed fireplace. No 

 fireplace can well be contrived more completely closed 

 than those of the iron stoves in common use in the 

 Netherlands ; but in these stoves, which are heated 



