THE NEOZOIC AGES. 275 



The advocates of floating ice as distinguished from a 

 continental glacier, merely dispense with the latter, 

 and affirm that the striation under the clay, as well as 

 that connected with the later boulders, is the effect of 

 floating bergs. The occurrence of so much drift wood 

 in the clay favours their view, as it is more likely 

 that there would be islands clothed with trees in the 

 sea, than that these should exist immediately after 

 the country had been mantled in ice. The want of 

 marine shells is a difficulty in either view, but may 

 be accounted for by the rapid deposition of the clay 

 and the slow spreading of marine animals over a sub- 

 merged continent under unfavourable conditions of 

 climate. 



In any case the reader will please observe that 

 theorists must account for both the interior and 

 marginal forms of these deposits. Let us tabulate the 

 facts and the modes of accounting for them. 



