ease of warm equatorial currents. But the near sun in winter acting
on an ice-clad surface would only increase the fogs and snow, while the
currents could only change if a large portion of the ice were first melted,
in which case they would no doubt be modified so as to cause a further
melting of the ice. Dr. Croll says: "The warm and equable conditions of
climate which would then prevail, and the enormous quantity of
intertropical water carried into the Southern Ocean, would soon produce a
melting of the ice." (_Loc. cit._ p. 111.) This seems to me to be assuming
the very point at issue. He has himself shown that the presence of large
quantities of ice prevents "a warm and equable climate" however great may
be the sun-heat; the ice therefore would _not_ be melted, and there would
be no increased flow of intertropical water to the Southern Ocean. The
ocean currents are mainly due to the difference of temperature of the polar
and equatorial areas combined with the peculiar form and position of the
continents, and some one or more of these factors must be altered _before_
the ocean currents towards the north pole can be increased. The only factor
available is the Antarctic ice, and if this were largely increased, the
northward-flowing currents might be so increased as to melt some of the
Arctic ice. But the very same argument applies to both poles. Without some
geographical change the Antarctic ice could not materially diminish during
its winter in _perihelion_, nor increase to any important extent during the
opposite phase. We therefore seem to have no available agency by which to
get rid of the ice over a glaciated hemisphere, _so long as the
geographical conditions remained unchanged and the excentricity continued
high_.

[57] In the _Geological Magazine_, April, 1880, Mr. Searles V. Wood adduces
what he considers to be the "conclusive objection" to Dr. Croll's
excentricity theory, which is, that during the last glacial epoch Europe
and North America were glaciated very much in proportion to their
respective climates now, which are generally admitted to be due to the
distribution of oceanic currents. But Dr. Croll admits his theory "to be
baseless unless there was a complete diversion of the warm ocean currents
from the hemisphere glaciated," in which case there ought to be no
difference in the extent of glaciation in Europe and North America. Whether
or not this is a correct statement of Dr. Croll's theory, the above
o