HISTORY OF THE DEE, WALES. 229 



the Lower and Upper Silurian rocks as occurring at one time for the 

 sake of convenience, there being no unconformity locally visible in this 

 area. There was no fault down the Menai Straits, though faults 

 occurred to the right and left of it. The point which Prof. 

 Seeley had raised was an important one, and one which it was 

 difficult to give a direct reply to. The Carboniferous strata, by 

 covering the tableland, would in a great measure tend to preserve it. 

 They probably thinned out towards Snowdon. 



