1878.] 
Glacial Drift in North America . 
69 
beds of later age. To the same horizon belong all the 
instances I have given of the earliest appearance of man in 
North America, and to it almost certainly must be ascribed 
the discoveries of Dr. Abbott and Mr. Wallace on the 
eastern sea-board. The extinCt 'mammals and the earliest 
appearance of man in North America are therefore pre- 
diluvial, as I have urged is the case in Europe : indeed a 
most striking parallel may be drawn between the series of 
events that happened in the Glacial period in the eastern 
and the western continent. 
We have first in Europe a great extension of land ice, 
that from Scandinavia reaching to the south of the Baltic, 
and that of the Alps to the Jura and down the valley of the 
Rhone as far as Lyons. We have then the retreat of the 
ice ; and palaeolithic man, the mammoth, and the rhinoceros 
occupying part at least of the area the ice had covered. 
Then we have a great outspread of gravels and clays, 
the latter in Northern Europe, with far-transported boul- 
ders, reaching up to 1700 feet above the present level of 
the sea. 
I have endeavoured to explain this series of events by the 
theory that whilst the ice was accumulating on the moun- 
tains of Scandinavia and Central Europe, it was also being 
piled up at the northern end of the Atlantic, and in greater 
abundance there because of greater precipitation. When 
it there reached a sufficient height to intercept the 
moisture in the air-currents travelling northward it would 
advance down the bed of the Atlantic, partly by flowing as 
a glacier, but principally because the precipitation was on 
the southern slope and increased as the ice-ridge progressed 
southward. Whilst this ridge of ice was moving down the 
bed of the Atlantic, that from Scandinavia and the Central 
Alps had culminated, and began to shrink back, for the area 
of greatest precipitation was now on the Maritime Alps, 
the Pyrenees, the Cantabrian Range, and the mountains of 
Asturias, and the accumulation of ice there intercepted the 
moisture that had before supplied the glaciers of Northern 
and Central Europe. This I consider was the time of the 
principal distribution of the mammoth and the woolly rhi- 
noceros, an earlier stage being marked by the presence of 
Elephas antiquus and Rhinoceros etruscus. The great accu- 
mulations of ice in the northern and southern hemisphere 
had before this abstracted so much water from the ocean 
that the level of the latter had been greatly lowered, the 
rivers cut deeper channels than they now occupy, the bed of 
the German Ocean was left dry, and many another traCt 
