Dr. Jcmies Geikie — Preservation of DeposiU under ' Till.^ 77 



with the interglacial beds at Ness and Garrabost ? The low grounds 

 in question are sprinkled solely with Till, and dotted with morainic 

 rubbish and erratics. Instead of marine deposits, we see only the 

 marks of a recent and severe glaciation. Every vestige of the 

 last interglacial occupation by the sea (with the two exceptions 

 mentioned) has been swept away by the ice-sheet, whose bottom- 

 moraine was rolled over the shell-beds at Ness and Garrabost. 

 And the principal mass of these deposits occurs in the very position 

 where, as I shall have occasion to point out moi'e particularly in 

 another place, the ice-sheet must necessarily have exerted less grind- 

 ing power. 



I have drawn attention elsewhere to certain remarkable facts con- 

 nected with the distribution of interglacial beds in North America, 

 and have pointed out that the researches of our fellow-labourers 

 in the States and Canada have proved that American interglacial 

 deposits occur in the same peculiar manner as our own : — they ai'e 

 absent or very rarely met with in the regions north of the great 

 lakes, and they increase in importance as they are followed south. 

 Quite recently Mr. G, Jennings Hinde, of Toronto, has described 

 some very interesting and important sections, which are exposed 

 upon the shores of Lake Ontario.^ These sections show no fewer 

 than three separate beds of Till with intervening stratified deposits, 

 the lower one of which has yielded many plant-remains and fresh- 

 water organisms. The section extends continuously along the shores 

 of the Lake for a distance of nine miles and a half, and the fossil- 

 iferous interglacial beds attain a thickness of 140 feet. Occasionally 

 they are violently contorted and confused, and in one place the 

 overlying Till cuts down into them to a depth of more than 100 

 feet — the breach occupied by the Till being about 450 yards in 

 breadth. Yet throughout the greater part of the section this over- 

 lying Till rests apparently quite conformably upon the stratified de- 

 posits, which then show perfectly horizontal and undisturbed bedding. 

 Here, then, we have a case where one and the same ice-sheet has 

 ploughed out incoherent strata, driving a deep and broad trench 

 through them, although here and there it has allowed them to escape 

 with only severe crumpling, contortion, and confusion, while in yet 

 other places it seems to have rolled its bottom-moraine quietly over 

 their surface in such a way as to leave the beds apparently un- 

 denuded and undisturbed. 



The same geologist writes me that '' up to the present time these 

 interglacial clays, etc., appear to occur only in the lake-depressions 

 and other localities at low levels. I cannot find them in the more 

 elevated districts, and supposing a fresh glacier now to creep over 

 this country, it would sweep before and beneath it the Till on the 

 uplands, and cover over the stratified clays in the present lakes with 

 this material ; and there would thus be a repetition of the same 

 arrangement of stratified beds and overlying Till as is now seen in 

 the present cliffs facing the lake." He thinks that the earliest 

 ice-sheet had more grinding power than the ice-sheets of later cold 

 1 Canadian Joui-nal, April, 1877. 



