1884.] i Recent Literature. 399 
what erosive power it had was exhausted in merely polishing off 
_ and puttying up the topography of the continent.” In this para- 
graph we havea reiteration of Professor Lesley’s well-known 
views, which, though somewhat extreme, are based, doubtless; 
_ on the condition of things in Pennsylvania at the former thin 
_ €dge of the continental glacier. Where, as in the Great Lake 
region, the ice was undoubtedly thicker and remained a much 
longer time, the erosion probably went much deeper. We still 
_ greatly need a systematic review of all the facts bearing on the 
_ thickness of the morainal matter in different localities over the 
_ €ntire glaciated area of North America. In the Rocky Mountain 
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t the whole country de/ow the level of 800’, or 750’ above tide, 
More or less covered with a post-glacial stratified deposit of 
modified drift, derived from the moraine and from the glacial drift 
with : were reéxcavated. Unimaginable floods poured southward 
“i, cessation along all the valleys, and spread out over the 
(R their burdens of moraine stones, rounded and smoothed 
~ ver and its affluent streams cut down through these post- 
deposits, as shown by the terraces which now border their 
