bjection certainly does not apply to the views here advocated; but as I
also hold the "excentricity theory" in a modified form, it may be as well
to show why it does not apply. In the first place I do not believe that the
Gulf Stream was "completely diverted" during the glacial epoch, but that it
was diminished in force, and (as described at p. 144) _partly_ diverted
southward. A portion of its influence would, however, still remain to cause
a difference between the climates of the two sides of the Atlantic; and to
this must be added two other causes--the far greater penetration of warm
sea-water into the European than into the North American continent, and the
proximity to America of the enormous ice-producing mass of Greenland. We
have thus three distinct causes, all combining to produce a more severe
winter climate on the west than on the east of the Atlantic during the
glacial epoch, and though the first of these--the Gulf Stream--was not
nearly so powerful as it is now, neither is the difference indicated by the
ice-extension in the two countries so great as the present difference of
winter-temperature, which is the essential point to be considered. The
ice-sheet of the United States is usually supposed to have extended about
ten, or, at most, twelve, degrees further south than it did in Western
Europe, whereas we must go twenty degrees further south in the former
country to obtain the same mean winter-temperature we find in the latter,
as may be seen by examining any map of winter isothermals. This difference
very fairly corresponds to the difference of conditions existing during the
glacial epoch and the present time, so far as we are able to estimate them,
and it certainly affords no grounds of objection to the theory by which the
glaciation is here explained.

[58] Dr. Croll objects to this argument, and adduces the case of Greenland
as showing that ice may accumulate far from sea. But the width of Greenland
is small compared with that of the supposed Antarctic ice-cap. (_Climate
and Cosmology_, p. 78.)

[59] The recent extensive glaciation of New Zealand is generally imputed by
the local geologists to a greater elevation of the land; but I cannot help
believing that the high phase of excentricity which caused our own glacial
epoch was at all events an assisting cause. This is rendered more probable
if taken in connection with the following very definite statement of
glacial markings in South Africa. Captain Ayl