27? 



Indeed the very considerable disengagement of heat, during the 

 decomposition of pyrites, will easily account for the natural accen- 

 sion of so combustible a body as coal, if in union with it whilst 

 such a process is going on. Thus Dr. Jordan, speaking in his Essay 

 on Mineral Waters, of the properties which coals possess, when 

 they contain much of the pyrites, or, as the colliers say, coal- 

 metal, of heating and even kindling upon the gradual accession of 

 moisture, or the affusion of water upon them, states, that several 

 such accidents have happened at Newcastle ; and he particularly 

 mentions a circumstance of this kind having occurred in London, 

 at Puddle-dock. Dr. Plott relates*, that at Ealand, in Yorkshire, 

 one Wilson having piled up many cart-loads of pyrites in a barn of 

 his own, for some secret purpose, perhaps to extract the gold, the 

 roof being faulty, and admitting rain-water to fall copiously in 

 among them, they first began to smoke, and at last to take fire, and 

 bum like red-hot coals, so that the town was considerably disturbed 

 and alarmed. 



To effect the dissipation of a considerable portion, if not the 

 whole of the inflammable matter, from vegetable and bituminous 

 masses, such a degree of heat may perhaps be sufficient as may 

 neither render the mass, nor the vapours which evolve from it, 

 luminous, but during the darkness of the night. The phenomena 

 described in the following account, related by John Stephens, M.A. 

 in the Philosophical Transactions -f, seems to point out such a gra- 

 dual decomposition of pyrites; and which, by charring the included 

 combustible matter, might be competent to the formation of the 

 peculiar coal here treated of. Mr. Stephens says, " that in the 

 month of August, 1751, the air, having been for some time remark- 

 ably hot and dry, was changed of a sudden by a heavy fall of 



* The Natural History of Staffordshire, by Dr. Thomas Plott, p. 142, 

 t Philosophical Transactions, vol. lii. p. 119. 



