1916.] 



THE DEPOSITS. 



385 



It is now necessary to try to give a meaning to these 

 deposits. The clays are strictly of local origin as are the 

 component parts of the "Head." They are the result of the 

 decomposition of the metamorphic rocks and rested on the 

 planed surfaces of the rocks while the ice was on the island. 

 As the ice became supported by water during the pre- 

 Mousterian submergence the clay, then enormously thicker 

 than now, came under the action of tidal and wave motion 

 and was suspended and distributed. The two clays cannot, as 

 far as the evidence goes, be separated as regards cause, for 

 both show that they rest on planed surfaces. 



The clays have suffered enormous erosion and this is very 

 much more in evidence in the low land of the Yale than on 

 the higher parts of the island. There are places where the 

 lower clay has been completely removed, but the place where 

 the remnants remain show that it was originally spread to a 

 great thickness over the whole island. A peculiar mound 

 existed at Hougue Forique where the clay, whether the upper 

 or lower I do not know, stood up abruptly on the land to a 

 height of 12 to 14 feet. This was levelled before I began to 

 study these deposits, so that I can only use the fact to show 

 how high the clays stood. 



That there were two separate deposits generally, not only 

 in the islands, can be shown by reference to several authors; 

 but I need not press the point for they can be seen here at 

 any time. 



DIAGRAM NO. 12. 



Showing upper Clay over the 50ft. beach. 



The details of the beds are shown in Diagram No. 10. 



