THE BOULDERS AND DRIFTS OF THE EDEN VALLEY. 693 



They generally show traces of having been piled up rather than 

 thrown down, as Mr. Goodchild supposes. The author denied that the 

 sea cannot throw down clays at angles of from 15° to 30°, and stated 

 his grounds for believing (with the Eev. M. H. Close) that the sud- 

 den disappearance of the ice-sheet can be better explained by the 

 encroachment of the sea than by the sudden melting of the ice. Bnt 

 the author's main argument against Mr. Goodchild's theory was 

 derived from the purity of the interiors of existing ice-sheets, as 

 shown by Professor Wyville Thomson and other eminent authorities. 



