ANCIENT GLACIERS IN EASTERN HEMISPHERE. 173 



be boulders which have been brought from beyond the 

 sea. This I find to be the case, and in two instances the 

 discovery of shells was preliminary to the extension of the 

 boundaries of the known distribution of boulders of trans- 

 marine origin. 



" The officers of the Geological Survey some years ago 

 observed the occurrence of ' obscure fragments of marine 

 shells ' in a deposit at Whalley, Lancashire, in which they 

 could find only local rocks. One case such as this would 

 be fatal to the theory of the remanie origin of the shells, 

 but on visiting the section with Mr. W. A. Downham, I 

 found, amongst the very few stones which occurred in the 

 shell-bearing sand at the spot indicated, two well-marked 

 examples of Cumbrian volcanic rocks, and, at a little dis- 

 tance, large boulders of Scottish granites. 



" The second case is more striking. The announcement 

 was made that shells had been found on a hill called Gloppa 

 near Oswestry, in Shropshire, and, as it lay about five miles 

 to the westward of Mackintosh's boundary of the Irish Sea 

 Glacier, and therefore well within the area of exclusively 

 Welsh boulders, it furnished an excellent opportunity of 

 putting the theory to the test. An examination of the 

 boulders associated with the shells showed that the whole 

 suite of Galloway and Cumbrian erratics such as belong to 

 the Irish Sea Glacier were present in great abundance. 

 Not only this, but in the midst of the series of shell-bear- 

 ing gravels I observed a thin lenticular bed of greenish 

 clay, which upon examination was found to be crowded 

 with well-scratched specimens of Welsh rocks ; but neither 

 a morsel of shell nor a single pebble of a foreign rock 

 could be found, either by a careful examination in the 

 field or by washing the clay at home, and examining with 

 a lens the sand and stones separated out. 



" The fact that predictions such as these have been veri- 

 fied affords a very striking corroboration of the theory put 

 forward ; and, though shells cannot be found in every 



