1866.] DAWSON— ICEBERGS AND GLACIERS. 41 



was submerged and that the valley of Lake Lenian was a strait 

 like Belle-Isle, traversed by powerful currents and receiving ice- 

 bergs from both Jurassic and Alpine glaciers, and probably from 

 further north. One or other supposition is required to account 

 for the appearances, which may be explained on either view. 

 The European hills may have been higher and colder, and changes 

 of level elsewhere may have combined with this to give a cold 

 climate ; or on the other hand, a great submergence may have left 

 the hills as islands, and may have so reduced the temperature by 

 the influx of Arctic currents and ice, as to enable the Alpine 

 glaciers to descend to the level of the sea. Now we have evidence 

 of such submergence in the beds of sea-shells and travelled boulders 

 scattered over Europe, while we also have evidence of contempo- 

 raneous glaciers in their traces on the hills of Wales and Scotland 

 and elsewhere, where they do not now occur. 



I have long maintained that in America all the observed facts 

 imply a climate no colder than that which would have resulted 

 from the subsidence which we know to have occurred in the 

 temperate latitudes in the post-pliocene period, and though I would 

 not desire to speak so positively about Europe, I confess to a 

 strong impression that the same is the case there, and that the 

 casing of glacier ice imagined by many geologists, as well as the 

 various hypotheses which have been devised to account for it and 

 to avoid the mechanical, meteorological and astronomical difficulties 

 attending it, are alike gratuitous and chimerical, as not being at 

 all required to account for observed, facts and being contradictory, 

 when carefully considered, to known physical laws as well as 

 geological phenomena.* 



Carrying with me a knowledge of the phenomena of the glacial 

 drift as they exist in North America, and of the modern ice drift 

 or its shores, I was continually asking myself the question — To 

 what extent do the phenomena of glacier drift and erosion resemble 

 these ? and standing on the moraine of the Bosson glacier, which 

 struck me as more like boulder clay than anything else I saw in 

 the Alps, with the exception of some recent avalanches, I jotted 

 down what appeared to me to be the most important points of 

 difference. They stand thus : — 



1. — Glaciers heap up their debris in abrupt ridges. Floating 



* Canadian Naturalist, Vols, viii and ix. Geological Magazine, December, 

 1865. 



