1874.] Climate of the Glacial Period. 425 
led me to the conclusion that the ice from the north 
blocked up the whole water-shed of Siberia as far as the 
borders of Kamtchatka. 
We thus find everywhere in the northern hemisphere that 
the ice thickened northwards, that it radiated from the pole; 
and that its margin nearly girdled the world, and probably 
would be found to have done so completely if there were 
land to preserve its traces. 
There are many geologists who believe that these northern 
lands were not all glaciated at the same time,—that, for 
instance, the Glacial period of North America was not con- 
temporaneous with that of Europe. Those who thus argue 
adopt, in some form or other, Lyell’s theory that the cold of 
the Glacial period was produced bya change in the distribu- 
tion of land and water. Thus Mr. Hopkins, in 1852, calcu- 
lated that if—by some change in the relative position of sea 
and land—the Gulf Stream could be diverted from its present 
northerly course, whilst northern and western Europe were 
submerged to the extent of 500 feet, and subjected to the 
influence of a cold current passing over the depressed area, 
the snow-line would descend to 1000 feet above the sea-level 
in Wales and the west of Ireland, and glaciers would reach 
the sea. Although this amount of change would be totally 
insufficient to account for the facts of the Glacial period, it 
may still be useful to point out that not a single scrap of 
evidence has been adduced to show that the Gulf Stream 
ever passed over any portion of Europe or America that is 
now dry land. 
Throughout the whole of the Tertiary period the conti- 
nents appear to have had much the same area and figure as 
they at present possess. Dana has also pointed out that, 
even so far back as the Jurassic period, the Gulf Stream 
exerted the same kind of influence upon the temperature of 
the North Atlantic as it does now. He considers that the 
existence of corals in the English oolites proves that the 
coral reef boundary extended 22 degrees of latitude beyond 
its present farthest northern point, and believes that the 
Gulf Stream must have aided in this result. Other facts 
indicate its existence and influence in cretaceous and tertiary 
times,—as, for instance, the representatives of the French 
Faluns on James’s River, in North America, denote a cooler 
climate in lat 37° N. than prevailed at the same time in 
lat.47°N.in Western Europe,—whilst in the glacial epoch the 
extent of the ice in Western Europe and Eastern North 
America curiously and suggestively conforms with the curve 
of the present isothermal lines due to its action. Just as 
