,342 G. W. Bulman — Glacial Geology, 



of Boulder clay, succeeded by a series of sands and gravels, whicli 

 are in turn overlaid by Boulder clay, the general relations of the 

 beds point rather to a partial sorting of materials produced under 

 one set of conditions than to such a great change as that implied by 

 a passage from a glacial to a mild climate. 



There is, in the first place, no sign of the denudation of the lower 

 bed of clay before the deposition of tbe sands and gravels, or of the 

 latter before the deposition of the upper clay. 



Secondly, the series of sands and gravels is neither so extensive 

 nor continuous as might be expected on tbe hypothesis of their inter- 

 glacial origin. 



At one end of the Blackpool section, for example, the only 

 separation between the upper and lower clay is a bed of sand a few 

 inches thick. 



Further, the separation into upper and lower Boulder-clay seems 

 merely local. In the first place, Mr. Eeade points out, that in a 

 description of the Blackpool section some years previously by Mr. 

 Binny, no separation of the clay by sand and gravel is given in one 

 particular part of the section where there is such a separation now. 

 He explains this on the supposition, that, as the section is now 

 several yards further inland, the separating beds now visible had 

 thinned out seawards. And he suggests the probability that if the 

 beds could be followed inland, the upper and lower clays would be 

 found to coalesce in a similar way. The probability of this is further 

 indicated by the sections in the neighbourhood. 



Thus Mr. Eeade describes one where "the Boulder-clay was 

 divided by very persistent seams of sand, though in places these 

 thinned out and the upper and lower beds coalesced and became 

 one without observable division." In other cases, " the shingle is 

 divided by patches of Boulder-clay ; " while " irregular sporadic 

 patches of sand occur in the clay." 



An artificial section at Sankey Bridge is thus described : — " The 

 Boulder-clay was here penetrated to 100 feet below the surface, 

 the last 20 feet showed 5 feet of sand mixed with coal-dust and 

 15 feet of clay with bands of gravel. A sand and gravel seam 

 2 feet thick was passed through about 53 feet from the surface. 



It is obvious, I think, that sands and gravel and boulder-clay 

 mixed up in this way cannot be referred to distinct glacial and inter- 

 glacial epochs. And if we admit a glacial origin for such patches 

 and layers of sand and gravel, we are bound to admit the possibility, 

 if not the probability, of a similar origin for the greater development 

 in the Blackpool section. 



The evidence of the fossils of tbese Lancashire Drift beds is also 

 against the hypothesis of a mild interglacial epoch. 



Thus Mr. Mellard Eeade after an extensive examination of the 

 Mollusca found in them, concludes that the intercalated sands and 

 gravels are not separable from the boulder clays by their organic 

 remains, as they clearly ought to he on the hypothesis of a mild inter- 

 glacial period. "My object," he writes, "in these preliminary 

 investigations was to ascertain if there were any organic remains 



