The icebergs, after gaining the temperate latitudes, are moved more or less eastward by the westerly winds and drift currents, and so are scattered over the southern temperate oceans, where the melting bergs impart whatever coldness they were able to store up while forming in the antarctic regions. The low sea-levels caused by the westerly winds to the leeward of New Zealand and to the leeward of Argentine, not only cause the ice-bearing currents to set northward, but they also cause the tropical currents to make considerable inroads into the high southern latitudes. This is the reason why the lands are less burdened with ice on the antarctic shores opposite Cape Horn than on other parts of that glaciated continent. The tropical currents which turn southward east of New Zealand largely mingle their waters with the great southern drift current, and so are carried through the Cape Horn channel. Owing to this cause, the antarctic lands abreast Cape Horn are less burdened with ice than other portions of the antarctic shores. Thus, were it not for this penetration of warm waters southward, the antarctic coasts south of Cape Horn, because of the great snow-fall of that region, would obtain heavier glaciers than other portions of the southern continent. But the time is slowly coming when, with a lower temperature, the ice-sheets on the lands in the vicinity of the South Shetlands will attain greater thickness than the glaciers on other shores of the antarctic continent. Hence it appears that, when the several agents for producing and distributing cold in the southern latitudes are taken into consideration, the immense and continuous storage of ice on the southern lands, which adds to the wide-spread fleet of icebergs that float the southern temperate seas, and also the vast movement of cold antarctic water into the temperate and tropical oceans in deep under-currents, combined with the increasing coldness of the westerly winds, are now slowly bringing about in the southern hemisphere a period of frigidity. CHAPTER II. HOW ICE PERIODS IN THE NORTHERN HEMISPHERE ARE BROUGHT ABOUT. A large number of geologists are of the opinion that during the whole of the Tertiary period the climate of the northern temperate and arctic latitudes was uniformly warm, without a trace of intervening frigid periods. I have before explained why the climate was made warm in the southern hemisphere during the Tertiary epoch, and how on the closing of that age, and subsequently, a considerable portion of the ocean waters had moved from the northern hemisphere into the southern.