IN THE INDO GANGKTIC MOUNTAINS. 403 



different shades of the same substance. If it were necessary to fix its place 

 - amongst a series of fanciful divisions that have no reference either to science 

 or utility, I would say, that some specimens appear to approach nearest to 

 the Conchoidal brown Coal of the Wernerians, were it not for the obvious ab- 

 surdity of calling a substance brown, the color of which is in reality of the 

 most perfect black. Other specimens, the smaller veins for instance, bear 

 considerable resemblance to jet, and a third set to Channel Coal, thus showing, 

 that in reality, these are distinctions without differences. The two species of 

 Mohs are, however, well marked, and, therefore, easily discriminated ; and 

 this not only by their chemical properties, but also by the more accessible 

 character of specific gravity. The bituminous Coal, when not contaminated 

 with foreign earthly ingredients, has a specific gravity below 1-4, the non- 

 bituminous, above. To the former, our mountain Coal belongs, and its pro- 

 portion of volatile ingredients, which I determine to be fifty-four per cent., 

 assigns it a place near the most perfect Coal. 



A practical division of the varieties of Coal has been : 1. Those which 

 burn with much flame, but do not coke, or leave cinders, the refuse being 

 a light ash. 2, Those which burn with less flame, but coke and leave 

 cinders. 3. Those which, like charcoal, burn without flame, and leave 

 a bulky and heavy a^h. The first, which is comprehended under the 

 bituminous species of Mobs, includes the Cannel Coal of Scotland, and 

 Wigam Coal of Lancashire. The second division is also comprehend- 

 ed under the bituminous species of Mohs, and includes New Castle, West- 

 moreland, and Staffordshire Coal. The third is the non-bituminous Coal; 

 the examples are Kilkenny Coal, Welsh Coal, and some varieties of Scotch 

 Coal. The Burdwan Coal belongs to the first division, as do also some 

 specimens of our mountain Coal, others again seem to burn with less 

 flame, besides having a higher specific gravity than belongs to Coals of this 

 class. 



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