1875.] Niagara. 155 
thousand years ago. In the northern temperate zone, so 
far as we can learn, there has been little variation in the 
animal or vegetable world since the glacial period. In the 
tropics, the formation of specific differences has been pro- 
bably more rapid, but in northern Europe, the species now 
living differ but little, if at all, from their pre-glacial an- 
cestors. Some of the large mammalia have become extin¢t, 
but the fauna and flora are essentially the same as they 
were before the glacial periods—that is, though some species 
have died out, we have no proofs of any new ones having 
come in. ‘There is not a single example of a distinét spe- 
cies having been formed since that time, though some 
varietal differences may be detected. Even man himself 
has, I believe, varied but little, physically, since pre-glacial 
times. 
In the paper already referred to, published in No. 44 of 
this journal (Oct., 1873), I assumed that the arguments 
brought forward by distinguished geologists, to prove that 
the palzolithic implements and the mammalian remains 
found with them were post-glacial, were founded on a sound 
data. There were great difficulties to be surmounted if 
that conclusion was correct; but the published sections of 
the superficial beds, at Bedford and at Hoxne, seemed to ad- 
mit of no other explanation. Since then I have been able to 
examine for myself some of the supposed post-glacial beds, 
and to devote more time to the study of the whole of the 
valley gravels in the south of England, at the bottom of which 
the palzolithicimplementsand mammalian remains are found. 
The conclusion at which I have arrived is, that so far as the 
British Isles is concerned, paleolithic man, the mammoth, 
the woolly rhinoceros, and the hippopotamus are entirely 
pre-glacial, and that the great and distinct break between 
the palzolithic and neolithic deposits in that area was caused 
by the culmination of the glacial period, when to the north 
of a line drawn irregularly from Lynn Regis, in Norfolk, 
through Birmingham westward, nearly the whole country 
was covered by land-ice, that destroyed the mammalian 
bones and the palzolithic implements, excepting where pre- 
served in fissures and caverns, or in a few spots in the 
eastern counties, to which the ice did not reach; and when, 
to the south of that line, a great lake or sea of fresh water, 
dammed back by the ice that blocked up the German ocean 
to the north, and the British Channel to the west, covered 
the pre-glacial remains beneath a mantle of beach gravels 
as it rose and fell. 
Dr. Falconer long ago argued that the older cave 
