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. Moggridge'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 explanations 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.
