934 H. K. JORDAN ON COAL-PEBBLES AND THEIR DERIYATION. 



Prof. Morris remarked that the subject brought forward by 

 Mr. Jordan was one of great interest. He thought there might be 

 three sources for these pebbles : — first, floating wood encased in 

 sandstone and carbonized ; secondly, the breaking up of submerged 

 forests, when the fragments became imbedded in sands and clays ; 

 and, thirdly, the breaking up of old coal-beds, and the distribution 

 of the fragments through younger deposits. 



The Author, in reply, stated that he could not accept Mr. Mog- 

 gridge's explanation, because the difference in the level of the 

 deposits referred to was due to changes subsequent to the formation 

 of the beds containing coal-pebbles. Nor could he adopt the ex- 

 planations suggested by Prof. Morris, because, had the pebbles been 

 so derived, it would be reasonable to expect their occurrence, more 

 or less, throughout the entire series of Coal-measures, whereas they 

 they were found associated only with seams of coal which had 

 coarse sandstone roofs. 



