422 Climate of the Glacial Period. (October, 
his powerful advocacy, after nearly half a century has 
elapsed, it still holds its ground amongst the rival views 
that have been advanced, and deserves our first con- 
sideration. 
Lyell takes for his starting-point the undoubted fact that 
the sea and the land are now in some parts changing places. 
Along some coast lines the land is either slowly sinking or 
has sunk in post-glacial times, whilst in others the conti- 
nents have been raised above their former level. He 
proceeds to show that the climate of a place is greatly 
dependent upon its position with respect to great masses of 
land or water; that an insular climate is less extreme than 
that of the interior of a great continent; and that currents 
of water from the tropics, or from the ar¢tic regions, are 
very effectual in raising or lowering the mean temperature 
above or below what is due to distance from the equator 
alone. He then considers what change in the relative 
position of land and water would produce the warmest 
and what the coldest climate, and comes to the con- 
clusion that if all the land was distributed around the 
equator we should have the warmest climate possible due 
to geographical conditions, and that if all the land was 
situated at and around the poles we should have the 
extreme of cold. 
There can be little doubt that if the second set of condi- 
tions prevailed, or even some approach to them, they would 
be effeCtual in rendering more severe the climate of polar 
regions, and in causing a greater accretion of ice than now 
prevails. A rise of polar and a submergence of tropical 
lands would certainly lower the temperature of the arctic 
regions. A mere rise-of land, sufficient to close Behring’s 
Straits and to connect America through Newfoundland with 
Europe, would, by shutting off all warm currents from the 
polar seas, tend to a greater accumulation of ice, as the 
heat of the Gulf Stream and other warm currents—that is 
now expended in tempering arctic seasons and melting polar 
ice—would then cause greater evaporation, and consequently 
greater precipitation, on the frozen lands of the north. 
But it must not be forgotten that the warm currents flowing 
northwards are counterbalanced by cold ones flowing south- 
wards; and if, on the one hand, regions enjoying a warmer 
climate through the influence of the Gulf Stream would then 
be shut off from its influence and subjected to greater cold, 
so, on the other, coasts—such as that of eastern North 
America—now cooled by polar currents, would be laved by 
warmer waters. Yet it is on the eastern side of North 
