H. B. Norton

“ ANCIENT moraines, striations denoting the action of vanished glaciers, the lost rocks, clay-beds evidently of glacial origin—all these are evidences testifying that at some period not very remote, as we count geological periods, the whole northern hemisphere down to the southern limit of 40° was submerged and covered with vast glaciers and ice-floes. There is not a living scientist of any eminence who questions the truth of this assertion. ”

“ We ordinarily speak of the earth's axis as being always parallel to itself. It is, in fact, however, subject to a very slow gyratory motion, caused by the attraction of the sun upon the meniscus, or ring of matter bulging at the equator, which motion is retrograde, or in an opposite direction to the revolution of the earth. ”

“ Nevertheless, we need not expect that mankind will then witness the utmost possible degree of refrigeration, because the ellipticity of the earth's orbit is now less than it has been at certain periods in the past, and will be again in the remote future. ”

“ Moreover, geologists affirm, that this inequality is increasing; they assert that the northern continents are slowly rising, and that the islands of the south Pacific are sinking. It is more probable that the water is slowly draining away from the northern hemisphere and accumulating in the southern. ”

“ It is evident that this plane will coincide with the line of the apsides once every 10,500 years; E is the winter solstice; F the summer solstice; C is the vernal equinox. While the earth is passing through B to D the north pole is inclined toward the sun. This period is the summer of the northern hemisphere.
D is the autumnal equinox. While the earth is passing from D through A to C, the north pole is inclined from the sun. This period is the winter of the northern hemisphere. In the southern hemisphere these seasons are reversed. ”

“ There is one more factor in this problem which must be considered, and that is the periodical variation in the ellipticity of the earth's orbit. Sometimes the line of the apsides is longer than at other times. This variation occupies regular but vast periods of time. It is evident that when the variation is greatest, the accumulation of ice at the winter pole must be most rapid. ”