8 



the purposes for which it is destined. Traces of vegetable 

 structure are rarely discoverable in coal, except in the 

 impressions of cactuses and of various dorsiferous and suc- 

 culent plants. 



Impartiality here requires that the opinion of Professor 

 Jameson on this subject should be noticed. The Professor, 

 speaking of the coal found in the neighbourhood of Edin- 

 burgh, says, " the coal, which is black coal, occurs in beds, 

 seldom more than a few inches in thickness, and is generally 

 contained in the bituminous shale or slate clay, rarely in the 

 sandstone. By the gradually increasing mixture of clayey 

 matter, it passes into bituminous shale. The accompanying 

 bituminous shale and slate clay contain impressions of ferns, 

 a fact which has been adduced in support of the opinion 

 which maintains the vegetable origin of black coal. We 

 are inclined to call in question the supposed vegetable origin 

 of this kind of coal, and are rather disposed to consider it as 

 an original chemical formation ; and that the occurrence of 

 vegetable impressions in the adjacent rocks no more proves 

 its vegetable origin, than the existence of fossil quadrupeds 

 in the gypsum of Paris proves that rock to have been formed 

 from the debris of animals of the class mammalia." * 



To these opinions it appears to be sufficient to oppose 

 the following deductions of Dr. Macculioch, from his expe- 

 riments on certain products obtained from the distillation of 

 wood, &c. The Doctor considers himself as authorised to 

 state, that, " Examining the alteration produced by water 

 on common turf, or submerged wood, we have all the evi- 

 dence of demonstration that its action is sufficient to convert 

 them into substances capable of yielding bitumen on dis- 

 tillation. That the same action having operated through a 

 longer period has produced the change in the brown coal of 



* Geognostical Description of the Neighbourhood of Edinburgh. 

 — Edinburgh Journal, vol. i. p. 354. 



