We have so far only considered the Northern Hemisphere. As every one knows, while we have Winter, the Southern Hemisphere has Summer. So at the very time we would enjoy the mild short Winters, the Southern Hemisphere would be doomed to experience Winters of greatly increased length and severity. As a consequence, immense fields of snow would be formed, which, by pressure, would be changed to ice, and creep away as a desolating glacier. It is quite true that the short Summer sun would shine with increased warmth, but owing to many causes it would not avail to free the land from snow and ice. As Mr. Geikie points out, “An increased amount of evaporation would certainly take place, but the moisture-laden air would be chilled by coming into contact with the vast sheets of snow, and hence the vapor would condense into thick fogs and cloud the sky. In this way the sun’s rays would be, to a large extent, cut off, and unable to reach the earth, and consequently the Winter’s snow would not be all melted away.” Hence it follows that at the very time the Northern Hemisphere would enjoy a mild interglacial climate, universal Spring, so to speak, the Southern Hemisphere would be encased in the ice and snow of an eternal Winter. But the earth has not always reached its perihelion point during the Winter season of the Northern Hemisphere. Owing to causes that we need not here consider, the earth reaches its perihelion point about twenty minutes earlier each year, so if it now passes its perihelion in Winter of the Northern Hemisphere, in about ten thousand years from now it will reach it in Summer, and in twenty-one thousand, years it will again be at perihelion in Winter. But see what important consequences follow from this. If during a period of high eccentricity we are in the enjoyment of short mild Winters and long pleasant Summers, in ten thousand years this would certainly be changed. Our Summer season would become short and heated; our Winters long and intensely cold. Year by year it would be later in the season before the sun could free the land from snow, and at length in deep ravines and on hill-tops the snow would linger through the brief Summer, and the mild interglacial age will have passed away, and again the Northern Hemisphere will be visited by snow and ice of a truly. Glacial Age. If, therefore, a period of high eccentricity lasts through the many thousand years, we must expect more than one return of glacial cold interspersed by mild interglacial climates.