Inflammables. 17 



IV. VARIETY. 

 Sulphureous Coal. 



This confifls of the former mixed with a 

 notable proportion of pyrites : hence it is apt 

 to moulder and break when expofed to the 

 air, and contains yellow fpots that look like 

 metal ; it burns with a fulphureous fmell, and 

 leaves red afhes, or a flag ; water ats upon 

 it after it has mouldered : its fpecific gravity 

 is 1,5, or more. 



Befides thefe varieties, fhiftus, micaceous 

 fhiftus, and gneifs are frequently found in 

 the neighbourhood of coal-mines fo penetrated 

 with petrol or bitumen as to conftitute an 

 inferior fpecies of coal, but the bitumen being 

 burnt, they preferve their form, and in fome 

 meafure their hardnefs ; I have alfo feen grey 

 flates fo foft as to be fcraped with the nail, 

 and which were greafy to the touch, that 

 burned like coal. 



All the different fpecies of coal arife from 

 a mixture of the varieties here enumerated. 



Note. That wherever coals exift, flates are 

 found near them, and fait or mineral fprings 

 pften in their neighbourhood. 



SPECIES X 



