84 Dr. Thomson on the Composition of [Aug, 



does not answer well for a very small fire ; but when a grate full 

 of splint coals are once thoroughly kindled they make an excel- 

 lent fire. 



3. Cherry Coal. 



This is, perhaps, upon the whole the most beautiful species of 

 Glasgow coal. It constitutes the greatest part of the four 

 uppermost of the Glasgow beds, especially the third and fourth 

 beds ; for the second bed contains a considerable proportion of 

 splint coal. I consider the Staffordshire coal as the same 

 species with the Glasgow cherry coal. In the neighbourhood of 

 Wolverhampton, it is employed for smelting iron in abundance. 

 No doubt, therefore, it might be used for the same purpose in 

 the neighbourhood of Glasgow, were it not that the splint 

 coal is found preferable in every respect. This species of coal 

 abounds likewise in Fife. The Edinburgh coal is probably 

 intermediate between splint and cherry coal. 



Colour velvet-black, with a slight shade of grey. 



Lustre in some places splendent ; in others shining : where 

 the lustre is shining, the coal has exactly the appearance of 

 caking coal ; but it is easily distinguished from that species by 

 not melting or becoming soft when heated. Kind of lustre 

 resinous. 



Principal fracture straight slaty. The different slates or 

 plates differ in their lustre ; some of them are splendent; others 

 only shining. The surface of both is smooth. When the lustre 

 is splendent, the surface is specular ; but when only shining, the 

 surface is merely even. Cross fracture mostly flat, conchoidal, 

 and specular splendent. In some places it has exactly the 

 aspect of wood charcoal. 



It is of about the same degree of hardness as caking coal. 

 Like it, cherry coal is very easily frangible ; so that there is a 

 good deal of waste in mining it ; and as it does not cake, the 

 small pieces are unsaleable, except for furnaces. At Birming- 

 ham, the loss in mining, including the pillars left to support the 

 roof, amounts to about two thirds of the whole. 



Fragments rectangular, and approaching the cubic form. 



Much more brittle than caking coal. 



Specific gravity 1*265. 



When exposed to heat, it readily catches fire, and burns with 

 a clear yellow flame, giving out a great deal of heat. The flame 

 continues till the coal is almost consumed, which takes place 

 much faster than when either caking coal or splint coal is 

 employed. Hence this coal makes the most rapid and the most 

 cheerful fire of the three ; but is by no means so economical. It 

 is easily distinguished from caking coal by not melting nor 

 becoming soft when heated. 



4. Cannel Coal. 

 This species has been long familiar in Great Britain, and is 



