382 



THE DEPOSITS. 



be seen on the tops of the valleys and on the slopes at a fairly 

 high level. 



The softer rocks are completely decomposed, the granite 

 or granitoid gneiss giving rise to gravels ; the felsitic gneiss 

 has become a mass of claj^ey material capable of being used 

 directly as a brick earth. The clay rests on the surface which 

 has been shorn off into straight lines on the flat that follows 

 the curve where it occurs on the slopes, but the shearing off by 

 ice is unmistakable. (See diagrams Nos. 10 and 11.) 



Diagram No. 10. 

 Clay Deposits at £t. Martin's Road. 



^ & o O O Oo*. 



« o 



2. O 



o D o z 



1, Eroded Rock surface ; 2, Boulder Clay 

 4, Upper Clay. 



3, Eroded Clay Surface 



Diagram No. II. 

 Clays in George Road. 



Showing how the two Clay deposits conform to the slope of the hill 

 once the straight eroded surfaces. 



The clay contains the pebbles of the 300 ft. beach and 

 also the boulders that the ice-cap formed from the detritus of 

 the rocks it destroyed. These boulders are always moved 

 from their original positions, but never very far, mostly about 

 half a mile. Their change of position cannot be a consequence 

 of the clay, but is the result of the movement of the ice-cap. 



