THE OBLIQUITY OF THE ECLIPTIC. lOQ 



far as to place the south pole in the midst of a vast ice-plain, the in- 

 coming clouds from the surrounding oceans would deposit most of their 

 moisture before reaching the centre, and the glacier would be built up 

 at or near its circumference. Hence we should expect to find the 

 glacier, instead of thinning gradually from twelve miles at the centre to 

 nothing at its outward edges, would present more the appearance of a 

 great section of a hollow sphere of nearly uniform thickness, laid over 

 the earth at the pole. 



"Further confirmation of this view is found in the fact that the 

 southern hemisphere has a cooler mean annual temperature than the 

 northern. Mr. Croll says this is due to the constant transference of 

 heat to the north by means of ocean-currents, nearly all the great 

 currents originating south of the equator ; while Sir Charles Lyell 

 thinks the true cause lies in the fact of the smaller extent of land 

 surface in the south. It is also true that from March 20 to Sept. 22 — 

 the duration of the sun's northern declination — there are 186 days, 

 while from the autumnal to the vernal equinox there are only 179 

 days : the northern summer is therefore seven days longer than the 

 southern summer, and the southern winter is that much longer than the 

 northern. If this inequality in the length of the summer and winter 

 in the two hemispheres had its origin during the glacial epoch, it would 

 at least have the effect of melting the ice in the north more rapidly 

 than in the southern hemisphere ; and if it existed before glacial times, 

 the effect would have been to accelerate the growth of the southern ice- 

 cap more rapidly than that of the northern. 



"At the culmination of the glacial epoch, therefore, Ave may assume 

 that the northern glacier Avas of an average thickness of 1 mile, and iu 

 extent about 25,000,000 square miles, making 25,000,000 cubic miles 

 of ice : that the area covered by the southern glacier Avas about 

 30,000,000 square miles, and 5 miles of average thickness, making 

 150,000,000 cubic miles of ice ; and the two extending over more than 

 one-fourth of the earth's surface, and aggregating 175,000,000 cubic 

 miles of ice. These two gigantic ' fossils ' avouUI be equal in siz \ to 

 about one-thirtieth part of the bulk of the moon, and avouIcI represent 

 an amount of evaporation from the Avater surface of the earth sufficient 

 to lower the sea-leA r el more than 5,000 feet, or about one mile. 



" Now, I submit that the attraction of the sun and moon upon this 

 mass of ice would, if continued for a long time, be sufficient to effect 

 some change in the direction of the earth's axis. Just how much that 

 change would be, I have not determined ; but that there would be some 

 change seems to be evident from the bare statement of the proposition. 

 When Ave consider that this matter has been removed to the poles from 

 the equatorial regions, the inequality of distribution of the earth's mass 

 Avould be greatly augmented. The action and re-action of the sun and 

 moon and the planets on the protuberant mass of matter about the 

 equator produce what is called ' nutation,' and the precession of the 

 equinoxes. Now, this mass being equally distributed around the earth 

 like a ring at the equator, only the nutation, or nodding, of the axis is 

 produced. But in case of the antarotic ice-cap the result of tli3 attrac- 

 tion would be somewh (.t different ; for, this being largely at one side o. - 



