190 ON THE ORIGIN OF COAL. 



animal substances, and thus colour with their 

 carbon the Black Shales, and the existence of a 

 bed of Pecten, Posidonia, and Goniatites, now 

 found lying in them. According to Sir H. De 

 La Beche's table, p. 403, in the appendix to his 

 Geological Researches, the Pecten is now found 

 in sands, sandy mud, and mud at depths from 

 to 20 fathoms ; so it is fair to assume that these 

 creatures lived in about 10 fathoms of water. 

 A gradually increasing rate of subsidence then 

 appears to have been in action during the for- 

 mation of the dark gray Soapstones, Rock Bind, 

 and Gorse-Hall Sandstone Rock. 



The section of St. George's colliery, plate III, 

 fig. 2, presents nearly similar dynamical and 

 statical conditions of the earth's surface to that 

 last described ; but the periods of repose appear 

 to have been more frequent, and the subsidences 

 more gradual, than in the former instance. The 

 phenomena, however, are, on the whole, so similar 

 that it will be unnecessary to go through all the 

 changes of the earth's surface, at the period they 

 were made, a second time, except by noticing 

 the Black Basses over the yard and three quarters 

 mines. These strata, by the immense mass of casts, 

 Cyprides, and disjointed teeth, scales, and bones 



