3.51 
arises from the profusion of fossil fruits and other vegetable 
remains of a tropical character found in the tertiary deposits; 
but when we reflect upon the existing Flora of South Ame- 
rica, this difficulty vanishes ; for the most luxuriant vegeta- 
tion there flourishes in the immediate vicinity of perpetual 
ice ; and if, in addition to this, the former configuration of 
the land caused some considerable rivers to take a northern 
course, the spoils of more genial climes would be brought 
to a higher latitude. I do not think it necessary to notice 
similar evidences afforded by mere ancient formations, as 
the coal measures; for it is, and probably for ever will be, 
beyond the limit of geological investigation, to trace the 
changes to which this globe has been subjected during the 
countless ages which have intervened. 
Dr. Wm. Alexander, of Halifax, observed that the 
theories advanced by Mr. Clay, if not conclusive, were 
extremely interesting, and calculated, if pursued, to throw 
much light upon a matter which admitted of considerable 
difi'erence of opinion. Whether it was possible that the 
erratic blocks spoken of might have covered the summits 
of icebergs, he would not take upon himself to say, but 
it seemed to him that they had more easy means of ex- 
plaining that fact than some others connected with the 
question. He had hoped that Mr. Clay's inquiries would 
have led him to some investigation as to the little drifts in 
the beds of the Calder. If he was to give an opinion as 
to their formation, he should say that they had been trans- 
mitted in former ages, when there was not the same uniformity 
on the surface. Some persons attributed them to the existing 
water courses and channels, whilst others believed them to be 
the eflfects of the deluge. It seemed to him highly probable 
that that change which excavated the earth, might have 
brought along with it those erratic blocks. He should be 
M 
