SPONTANEOUS COMBUSTION. 361 



and stacks of corn have been frequently consumed by the 

 heat generated during the fermentation produced from 

 moisture; and gunpowder magazines, barns, and paper- 

 mills have been often burnt by the fermentation of the 

 materials which they contained. Galen informs us that 

 the dung of a pigeon is sufficient to set fire to a house, 

 and he assures us that he has often seen it take fire when 

 it had become rotten. Casati likewise relates on good 

 authority, that the fire which consumed the great church 

 of Pisa was ^occasioned by the dung of pigeons that had 

 for centuries built their nests under its roof. 



Among the substances subject to spontaneous combus- 

 tion, pulverized or finely-powdered charcoal is one of the 

 most remarkable. During the last thirty years no fewer 

 than four cases of the spontaneous inflammation of pow- 

 dered charcoal have taken place in France. When char- . 

 coal is triturated in tuns with bronze bruisers it is reduced 

 into the state of the finest powder. In this condition it 

 has the appearance of an unctuous fluid, and it occupies a 

 space three times less than it does in rods of about six 

 inches long. In this state of extreme division it absorbs 

 air much more readily than it does when in rods. This 

 absorption, which is so slow as to require several days for 

 its completion, is accompanied with a disengagement of 

 heat, which rises from 340 to 360 nearly of Fahrenheit, 

 and which is the true cause of the spontaneous inflam- 

 mation. The inflammation commences near the centre of 

 the mass, at the depth of five or six inches beneath its 

 surface, and at this spot the temperature is always higher 

 than at any other. Black charcoal strongly distilled 

 heats and inflames more easily than the orange, or that 

 which is little distilled, or than the charcoal made in 

 boilers. The most inflammable charcoal must have a 

 mass of at least 66 Ibs. avoirdupois, in order that it may 

 be susceptible of spontaneous inflammation. With the 



2 B 



