Theories of Formation of Coal. 97 



some cases as much as thirty feet long, with their leaves or 

 rootlets attached. 



Theories of the Formation of Coal. 



It is scarcely possible to visit a coal-field, or to read the 

 description of one, without being led to theorize on its mode 

 of formation. The origin of coal has long been a subject of 

 great difficulty, nor has any theory been yet advanced with 

 which it has been possible to reconcile all the appearances 

 which the coal-measures exhibit, all the variety of forms in 

 which coal is found. Indeed the more closely we examine 

 the phenomena, the more do we feel the distance we are 

 from a satisfadtory explanation of them. According to some 

 geologists, coal-seams and their accompanying strata are 

 accumulations of land plants and stony detritus carried down 

 by rivers into estuaries, and deposited in the sea, where the 

 vegetable matter undergoes changes that convert it into 

 coal. Others are of opinion that coal is the altered residuum 

 of trees and smaller plants that have grown on the spot 

 where we now find them ; that the forests were submerged 

 and covered by detrital matter, which was upraised to form 

 a foundation and a soil for another forest, to be in its turn 

 submerged and converted into coal, and that thus the alter- 

 nations which the vertical section of a coal-field exhibits are 

 to be accounted for. 



In the works of the last year to which I have chiefly re- 

 ferred, we find the former theory maintained by Sir R. Mur- 

 chison as most generally applicable ; Mr Lyell is more inclined 

 to adopt the latter. Sir R. Murchison dwells upon the facts 

 of the alternations of coal with limestones containing marine 

 remains, which are so frequently met with in most countries 

 where coal-fields prevail ; and as a striking instance of this, 

 he refers to the Donetz coal-field, which I have already alluded 

 to. A remarkable example of a similar kind, occurring in 

 Maryland, is mentioned by Mr Lyell. At Frostburg, a black 

 shale, ten or twelve feet thick, full of marine shells, rests on 

 a seam of coal about three feet thick, and 300 feet below the 

 principal seam of coal in that place. The shells are refer- 

 able to no less than seventeen species, and some of them are 



VOL. XLI. NO. LXXXI. — JULY 1846. G 



