OP THE N.W., MIDL.Vl^D, AND EASTERN COUN'TIES. l79 



in many places covers the middle sand-and-gravel formation, as 

 around Whittington, Oswestry, &c. South of Ellcsmere it capriciously 

 caps the large sand-and-gravel mounds (eskers ?), covers portions 

 of their sides, or lurks in the hollows between them ; but the sharp 

 line between the npper clay and the underlying gravel or sand, so 

 strikingly displayed all around the Irish Sea, is frequently absent. 

 The subglacial mud, or source of supply in the Lake-district (to 

 which the uniform character of the clay over extensive areas is 

 chiefly owing), would appear to have been carried by the currents 

 which floated the boulder- laden ice in a southerly direction by way 

 of Whitchurch and Shrewsbury to Berrington, where the Upper 

 Boulder-clay is scarcely distinguishable in appearance from the 

 horizontally continuous formation in Cheshire and Lancashire*. 

 In the extensive clay-pits lately opened near the Shrewsbury new 

 barracks the clay is a facsimile of the Upper Boulder-clay of 

 Cheshire and Lancashire, and the same in composition with the 

 exception of the absence of lime, which apparently did not fi.nd its 

 way from the Carboniferous rocks of the southern border of the Lake- 

 district so far south as Shrewsbury. In these claj'-pits there is 

 generally a sharp line between the clay and the underlying sand, 

 which in some places is contorted, and which is said to reach a 

 thickness of 90 feetf. Most of the erratics in the clay are from the 

 Welsh borders. Not more than one out of several hundred consists 

 of granite J. The stones are generally angular or sub angular ; and 

 exceedingly few of them are flattened or distinctly striated. jN'ear 

 the ferry, a short distance south of the Shrewsbury Welsh bridge, 

 the upper clay, somewhat in the form of a wrapper, covers a large 

 mound of shelly sand and fine gravel, in the lower part of which several 

 granite (Eskdale and Criffel) boulders have been found (see fig. 1). 

 The upper clay, more or less underlain by sand, is well represented 



Fig. 1. — Section near tJie Shrewsbury Welsh Bridge. 



A, Upper Clay. B. Sand and fine grayel. C. Talus. 



* I had not discovered this southerly extension of the upper clay when my 

 paper on sections around the estuary of the Dee (Quart. Juurn. Geol. Soc. for 

 Kovember 1877) "was -written. 



t The sand contains streaks and fragments of coal. 



\ Granite, however, is rather abundant in the lower unstratified gravel of 

 the neighbourhood. 



