and that the
mean winter temperature was not below zero.

It will hardly be necessary for me to review here the various theories
which have been advanced by geologists and botanists to account for this
remarkably high temperature in such northern latitudes. Any one who has
read the writings of the late Dr. Croll cannot help being struck by the
facts he adduces to show the importance of ocean currents in relation to
the distribution of heat over the globe, and it seems to me that the
view which attributes the mild climate prevailing in former times in
Greenland to warm ocean currents reaching the Polar Circle is the one
least open to serious objections. If we suppose that the North Atlantic
Ocean was bridged by a land-connection between Scandinavia and Greenland
by way of Spitsbergen, and between Greenland and North America, the
Polar Ocean would be practically a closed sea. If, then, a wide passage
existed somewhere about Behring Straits to allow a warm current to enter
and circulate within the Arctic Seas, we should have the southern shores
of Greenland washed by the warm Atlantic current and the northern shores
by a warm Pacific current, which combination would undoubtedly produce
the effect of raising the temperature throughout the Polar Regions very
considerably; and especially would that be the case with regard to
Greenland and the neighbouring islands.

It might be urged that the constant darkness during winter must have had
an injurious action upon the flora, but it is found that in countries
such as Northern Russia, where southern plants are housed during winter
in greenhouses, the light being almost entirely excluded by a covering
of straw, no serious damage is done thereby to the plants.

It seems probable that a similar gradual refrigeration of climate in
northern latitudes has taken place after Miocene times as has been
proved to have occurred in Europe.

Some years ago Dr. Haacke propounded the hypothesis that the centre of
creation of all the larger groups of animals was situated in the region
of the North Pole, and that the newly originated groups must always push
the older ones farther and farther south into the most remote corners of
the earth. As instances of the correctness of his view he quotes the
fact that the more ancient mammals, such as Monotremes, Marsupials,
Lemurs, Edentates, and Insectivores, all inhabit the more southerly
parts of the world. The Apteryx, Moa, Rhea, and the Ostrich, as we