388 W. SHONE ON THE GLACIAL DEPOSITS OP WEST CHESHIRE. 



known as hardly to require mention. The condition in which 

 Mr. Eeade has described the Mollusca as occurring in the Liver- 

 pool Boulder-clay is so exactly similar to that in which the 

 shell-fragments occur in the Boulder-clays of Newton and Daw- 

 pool that I might copy his remarks word for word. I shall therefore 

 simply refer to his paper (Quart. Journ. Geol. Soc. vol. xxx. p. 31). 



With regard to the shells in the Boulder-clays, all observers are 

 agreed that they are not in situ, and that they have been trans- 

 ported ; but how ? 



I think that the Boulder-clays bear every evidence of deposition 

 in still water, the particles which compose them being for the most 

 part very fine. For instance, if a piece of Boulder-clay be dissolved 

 in a test-tube filled with sea-water, and then shaken up, it is some 

 time before the fine unctuous mud is redeposited. I think this is a 

 very important fact, when we consider that the Upper Boulder-clay for 

 the most part is spread out in one uniform sheet over the lowlands 

 of Lancashire and Cheshire from the sea to a height of some 500 or 

 600 feet. I cannot imagine currents at once strong enough to 

 sweep along the shells from the then existing beaches, and at the same 

 time allowing the finest particles of the clay to be deposited. Again, 

 the Gastropoda throughout this clay are usually filled with the very 

 finest greyish-white sand full of Microzoa ; would not these currents 

 in rolling them along have swept out this fine greyish- white sand 

 and replaced it with the red Boulder-clay in which they lie im- 

 bedded ? as it is, however, those filled with Boulder-clay are the 

 exception, instead of being the rule. This argument is also equally 

 applicable to those who maintain that the Upper Boulder-clay is 

 derived, together with its shells, stones, striated erratics, and 

 Scandinavian fauna — in short, that it is not a glacial clay at all. 



The mode of the transportation of the shells in face of all these 

 difficulties has long been a puzzle. In the early part of 1875 there 

 was a short, but for the time a very severe frost. At the mouth of 

 the Dee there is an island called Hilbre, some five acres in extent ; 

 it is distant across the sands about a mile and a half from the Che- 

 shire shore ; this space is covered with water at half-tide. The dead 

 shells of the Mollusca, Ostracoda, Foraminifera, &c. which live in 

 the Laminarian zone are cast up and left by the receding tide 

 between the ripple-marks on the sands. The dead shells of the 

 Gastropoda, as they lie in these hollows, get more or less filled with the 

 fine silt containing the Microzoa. The frost was severe enough to 

 freeze the water left in these furrows by the receding tide ; conse- 

 quently the Gastropoda filled with this silt, the broken shells, &c. 

 were enclosed in thin sheets of ice, which were broken up on the 

 return of the tide, and such as were cast ashore on Hilbre Island 

 were piled together and frozen into blocks. When the thaw com- 

 menced it set these blocks free. Charged with the Gastropoda and 

 broken shells, these tiny ice-rafts floated short distances away, 

 distributing as they melted their load of broken shells, and casting 

 the silt-filled Gastropoda over the mud-flats of the delta of the Dee. 



I do not think I can offer a better explanation than this of the 



