G58 MR DAVID MILNE HOME ON THE BOULDER-CLAY OF EUROPE. 



has at last yielded up its secret. It is a land deposit, formed at the period when 

 Scotland, like Spitzbergen, lay beneath an immense covering of ice, which wrapped 

 the whole face of the country, hill and dale. Underneath such a covering, possibly 

 thousands of feet in thickness, the rocks would be ground down, and the boulder- 

 clay formed. Thus the absence of fossils is accounted for ; inasmuch as none 

 of our usual forms of life could exist beneath such an ice-sheet ; and thus we see 

 also how the clay is so peculiarly hard and untractable." (P. 630). 



I have briefly sketched the various theories relating to boulder-clay, to show 

 the difficulty of the subject, and have referred more particularly to the views of 

 the latest writers whose^ geological experience and knowledge are held in just 

 repute. 



It is, therefore, with considerable hesitation that I venture to call in question 

 the soundness of these views, and I would not have done so, had it not been that 

 some observations, bearing on the subject, do not appear to me to have received 

 sufficient consideration. Most of the observations to which I allude are to be 

 found scattered through different publications, and have never yet been brought 

 together, so as to throw a combined light on the question ; — I am able also to 

 adduce some observations of my own, not yet published. 



I shall advert, first, to the difficulties which beset the theory that our Scotch 

 boulder-clay "is a land deposit," the product of glaciers ; and will afterwards 

 state the reasons which lead me to believe that it has been formed at the bottom 

 of the sea — by the action of floating ice. 



I disavow any originality in presenting the iceberg theory. Moreover, it has 

 this presumption against it, that, having been formerly adopted by Mr Geikie, he 

 has lately intimated that he has had to abandon it, because, as he says, "though 

 the iceberg hypothesis is generally the accepted explanation of the phenomena of 

 striated rocks and boulder-clay, its untenableness seems to me completely estab- 

 lished." ("Glacial Drift," p. 10.) 



Notwithstanding this very decided condemnation, I think there are good 

 grounds for upholding the correctness of the iceberg hypothesis. 



That there are some points not altogether explained by it, I will not deny ; 

 but that there are insuperable difficulties with which the glacier hypothesis has 

 to contend, I shall now proceed to show — 



1. If the boulder-clay was formed, as is alleged, by the action of glaciers ; if it 

 consists of debris derived from the rocks which the ice grinds down in its passage 

 over them, and which are pushed forward by its ice-foot, we would see boulder- 

 clay now forming in those countries where glaciers are in action. But it has never 

 been alleged that in Switzerland, Norway, or Upper India, whose glaciers have 

 been described by competent observers, anything like boulder-clay is seen to be 

 produced. I have been twice in Switzerland ; and, being anxious to watch the 

 effects of glaciers on the rocks, made them a subject of study, and penetrated 



