ON -BITUMENS, &C. \Q\ 



The Bovey coal is commonly of a chocolate-brown, and fome- External cha- 

 times almoft black. The quality and texture of it are various r c a o ^ ers of Bo7e y 

 in different ftrata; from fome of thefe, it is obtained in the form 

 of firaight flat-pieces, three or four feet in length, refembling 

 boards, and is therefore called Board Coal. Others have an 

 oblique, wavy, and undulating texture, and, as Dr. Milles ob- 

 ferves, have a ftrong refemblance to the roots of trees, from 

 which, moft probably, this fort has in a great meafure been 

 formed. 



Some kinds alfo appear to be more or lefs intermixed with 

 earth ; but that which produces the moft powerful and lading 

 fire, is called ftone coal ; it is black, with a gloffy fracture ; 

 has little or none of the vegetable texture ; is more folid 

 and compact than the others, being almoft as heavy as fome 

 of the pit coals, the nature of which it feems very nearly to 

 approach. 



For chemical examination, I felecled fome of the coal which 

 had a wavy texture, and rather a gloffy fracture; the quality of 

 this fort being apparently intermediate between the others, as 

 it retains completely the marks of its vegetable origin, while, 

 at the fame time, it poffeffes every perfect character of this 

 fpecies of coal. 



A. 200 grains of the Bovey coal, by difiillation, yielded, Chemical exa- 



Grains. J^f^f 



1. Water, which foon came over acid, and afterwards 

 turbid, by the mixture of fome bitumen - - 60 



2. Thick brown oily bitumen - - - - 21 



3. Charcoal 90 



4. Mixed gas, confirming of hydrogen, "i 



carbonated hydrogen, and carbonic I eftimated at 29 

 acid, J 



200. 

 The charcoal, in appearance, perfectly refembled that which 

 is made from recent vegetables. By incineration, about 4 

 grains of yellowiQi allies were left, which confified of alumina, 

 iron, and filica, derived moft probably from fome fmall 

 portion of the clay ftrata which accompany the Bovey coal. 



of deficcation ; this, I believe, has not hitherto been much conft- 

 dered, but I am inclined, from many circumftances, to attribute 

 to it a very great degree of power. 



But 



