Submergence. 



413 



Prestwich found marine shells in sand and gravel at a 

 height of about 1,200 feet. I have visited the place, 

 and saw the shells in situ ; and at Congleton, 600 feet 

 above the sea, I also found sea-shells. 



Similar shell-bearing deposits at a low level are 

 found near the Mersey at Blackpool, and on the coast 

 north of the Kibble, and I have also observed them in 

 Caernarvonshire in the district of Lleyn. In the same 

 county similar deposits were found by the late Mr. 

 Joshua Trimmer, about five miles SE. of Caernarvon, 

 near the summit of Moel Tryfan, at a height of about 

 1,170 feet above the level of the sea. With that locality 

 I have been long acquainted, and in 1876 I revisited 

 it along with Mr. Etheridge. The section occurs at a 

 slate quarry in the Cambrian rocks.' This, after being 

 long abandoned, has of late years been worked with 

 vigour, and the result is, that good sections are exposed 

 as the gravel and boulder-clay are gradually cleared 

 away from the surface. In August 1876 the section 

 was as follows : 



FIG. 84. 



CL <l! ' ; 



1. Cambrian slate. 2. Shell-bearing sands and gravels. 

 3. Glacier Boulder-clay. 



The sands and gravels are all marked by oblique 

 lamination (false bedding) and have a beach-like as- 



