2 Mr. W. Hadfield's Observations on the Circumstances 



If 20 or SO cwt. of charcoal, in a state of minute division, be 

 put together in a heap and left undisturbed, spontaneous com- 

 bustion generally ensues. The fact has been long known ; but 

 no investigation, with the exception of that to which I have 

 referred, has, to my knowledge, been instituted. 



Spontaneous combustion does not often take place in what 

 the manufacturers call round charcoal; that is to say, in frag- 

 ments of considerable size ; unless when large quantities are 

 laid together, under which circumstances it is not very un- 

 usual. In this case the phenomenon is generally ascribed by 

 the makers to the charcoal not having been sufficiently cooled 

 after its production. This reason is, no doubt, sometimes, but 

 not always, correct. On the contrary, I have known charcoal, 

 which has been freely exposed to the atmosphere for several 

 days, enter into a state of ignition, when, though closely 

 watched, it presented in the interval no appearance of the 

 kind. 



In one case charcoal was loaded in Manchester, and con- 

 veyed by a cart to a distance of twenty miles. No combustion 

 appeared during the loading, nor could the carter, though he 

 carefully examined, perceive any indication of it, when, at 11 

 o'clock, he left it for the night. At 5 o'clock on the following 

 morning, however, he was called up to save his cart, which he 

 found on fire and nearly consumed. 



This charcoal had been made three days before the acci- 

 dent. Care had been taken that it should be sufficiently cool 

 before it was loaded, as a similar event had previously occur- 

 red to the same parties, who ascribed it to the charcoal being 

 too new, when, as they conceived, fire lurked in it unextin- 

 guished. 



These two instances may, I should think, be accounted for 

 in the following manner : — 



When large quantities of charcoal, as in the first example, 

 are laid together, it is evident that the lower parts must be ex- 

 posed to pressure, and, by the motion of the cart, to friction 

 from the parts above; in this way, therefore, a portion of the 

 charcoal is pulverized, forming a compact mass at the bottom, 

 where it enters into spontaneous combustion. 



In the second instance, pressure and friction had still greater 

 influence. The carter, while he was loading, beat down the char- 

 coal with a large hammer, to force it into a smaller compass. 

 Conveyed for twenty miles in a cart, the pieces would rub 

 against each other, and the finer parts would be shaken to a 

 compact mass ; and possibly the friction might, in this case 

 particularly, produce a degree of heat which might promote 

 the ignition. 



