1866.1 DAWSON — ICEBERGS AND GLACIERS. 43 



up the natural slope, the presence of marine shells, and the 

 mechanical and chemical character of the boulder clay. In short, 

 those who regard the Canadian boulder clay as a glacier deposit, 

 can only do so by overlooking essential points of difference between 

 it and modern accumulations of this kind. 



In conclusion, I would wish it to be distinctly understood, that 

 I do not doubt that at the time of the greatest post-pliocene sub- 

 mergence of Eastern America, at which time I believe the 

 greater part of the boulder clay was formed, and the more important 

 striation effected, the higher hills then standing as islands would 

 be capped with perpetual snow, and through a great part of 

 the year surrounded with heavy field and barrier ice, and that in 

 these hills there might be glaciers of greater or less extent. Fur- 

 ther it should be understood that I regard the boulder clays of 

 the St. Lawrence valley as of different ages, ranging from the 

 early post-pliocene to that at present forming in the gulf of St. 

 Lawrence. Further, that this boulder clay shows in every place 

 where I have been able to examine it, evidence of sub-aquatic 

 accumulation, in the presence of marine shells or in the unweathered 

 state of the rocks and minerals enclosed in it, conditions which, in 

 my view, preclude any reference of it to glacier action, except 

 possibly in some cases to that of glaciers stretching from the land 

 over the margin of the sea, and forming under water a deposit 

 equivalent in character to the ' boue glaciare ' of the bottom of 

 the Swiss glaciers. But such a deposit must have been local, and 

 would not be easily distinguishable from the marine boulder 

 clay. While writing these notes I have had the advantage of 

 reading the interesting papers of Messrs. Jamieson, Bryce and 

 Crosskey, on the boulder clay of Scotland,* which in character and 

 relations so closely resembles that of Canada, but I confess several 

 of the facts which they state lead me to infer that much of what 

 they regard as of sub-aerial origin must really be marine, though 

 whether deposited by ice-bergs or by the fronts of glaciers ter- 

 minating in the sea, I do not pretend to determine. It must 

 however be observed that the antecedent probability of a glaciated 

 condition is much greater in the case of Scotland than in that of 

 Canada, from the high northern latitude of the former, its more 

 hilly character, and the circumstance that its present exemption 

 from glaciers is due to what may be termed exceptional and acci- 



* Journal oi Geological Society for August, 1865. 



