94 Correspondence — Mr. G. Linnarsson. 



and the associated phenomena near enough, and having their bear- 

 ings pointed out to himself by an experienced guide. As they have 

 now been written, and published in a Journal of such a standing as 

 the Geological Magazine, they ought not to be altogether un- 

 answered, though I think that most of your readers do not need to 

 have the failings of such reasonings pointed out. 



The chief argument of Professor Milne against the glaciation 

 theory seems to be that that theory requires great climatal changes, 

 the explanation of which would involve insuperable difficulties. I 

 admit that Science has not yet given a final explanation of these 

 changes, but they are a well-established fact, and a fact must be 

 accepted, whether we can explain it or not. As for myself, I think 

 that the physical features — such as the nature of the Till and the stria- 

 tion of the rocks — are in themselves sufficient proofs of a former glacial 

 climate, but there are, besides, ample palseontological evidences. Some 

 thirty years ago, Professor Loven found that certain shell-banks in 

 Southern Sweden contain a completely'' Arctic fauna, and the labours 

 of the Geological Survey of Sweden have shown that the stratified 

 clay reposing on the gravel-beds is everywhere characterized by the 

 well-known shell Yoldia arctica, Gray, which occurs living only in 

 the most Arctic regions, as the coasts of Spitzbergen and those of 

 northern Greenland. Still more striking proofs of a former glacial 

 climate have been, in later years, adduced by Dr. Nathorst, who has, 

 from debris in the lacustrine deposits, found that a vegetation 

 identical with that now prevailing in Spitzbergen [Dry as octopetala, 

 Salix polaris, etc.) once lived not only in the lowlands of Southern 

 Sweden but also in Denmark. This being the case, it cannot be 

 doubted that a climate cold enough to produce a continental ice-sheet 

 once prevailed so far south as in Southern Sweden. 



That, actually. Till is formed, and rocks polished arid striated by 

 glacier-ice, is so well known from observations in the Alps and 

 elsewhere, that I think Professor Milne himself cannot deny its 

 capability of producing such effects. He points, however, to one 

 circumstance, often observed in connexion with these phenomena, 

 which he thinks not accountable for by the action of glacier-ice, 

 viz. the occurrence of erratic blocks raised to positions above the 

 rock from which they were derived. He explains their occur- 

 rence by the " action of coast-ice upon a rising area." If there 

 should be any meaning in this, Professor Milne ought to have called 

 for a sinking area instead of a rising, as, of course, the question 

 must be of the relative height. If a block is attached to floating- 

 ice, and the land is rapidly sinking, the block may be deposited in a 

 relatively higher position than that of the parent rock, but not if 

 the land is rising. There are, however, many instances of blocks 

 derived from lower positions, in places where the water never 

 reached. Thus, in Westrogothia blocks of the Cambrian Sandstones 

 are often found reposing on the summits of the Silurian mountains, 

 several hundred feet above their parent rocks, on heights which 

 the sea never reached in post-Tertiary times; and many similar and 

 still more striking instances are recorded from other countries by 



