GLACIAL PERIOD AND GRAVELS. 183 



like stones which have travelled in the sides or 

 bed of a Glacier. The deposit is often indis- 

 tinguishable from the clay found in Alpine val- 

 leys, from which Glaciers have retired which once 

 covered the country. The high ground in every 

 land in which Boulder Clay is found supports this 

 inference with evidences of the work of ice. 

 The Mountains of Scotland, the Lake district 

 of England, and the Snowdon district in Wales 

 smoothed and grooved by sheets of ice which 



have passed away. Small joints in the old slates 

 have been widened and deepened in the valleys, 

 until rounded Structures have been produced like 

 the backs of huddled sheep at rest. This condi- 

 tion known as Roches moutonn/es is sometimes 

 exposed by a retreating glacier in the Alps, and 



i> manifestly due to the work of frost and 



ier ice. 



Above many a mountain valley, Mich as the 



- of Llanberis, angular stones are perched in 



positions where water COUld have left 



them. The irded as ha en the 



atones of moraines 01 on the surface 



a glacier, and left behind in their present 



places when the ice melted beneath them. The 



crystalline rock above Neuchatel 



of the Mime MibMance as the Mont Diane 

 chain, and could only have reached their present 



lion upon the limestone chain of the Jura by 

 Crossing the central valley of Switzerland. On 

 such evidence Glacial conditions for a country 

 may be inferred even though boulder clay is not 

 seen. 



In North America Sir J. W. Dawson has 

 described the evidences of the Canadian ice-age 

 as comprising, (i.) a Lower Boulder Clay, which 



