GEOLOGICAL CLIMATE. 293 



prove (and there seems fair reason to believe they 

 prove) a glacial climate to have prevailed at one 

 time in some part or parts of India, surely the 

 15000 feet elevation of a district required to 

 account for it in that way is a smaller assumption 

 than the 35000 feet diminution of distance from 

 the earth's centre to the surface for thousands of 

 miles round the locality needed to bring the 

 pole to that region. 



But the astronomical cause invoked by Herschel 

 must have had, and must now have, its effect. It 

 does not go for nothing that we are nearer the 

 sun by one thirtieth of the mean distance in the 

 midwinter than in the midsummer of the northern 

 hemisphere, and in the midsummer than in the 

 midwinter of the southern hemisphere. Eleven 

 thousand five hundred years ago this was reversed : l 

 and if the distribution of land and water were then 

 the same or nearly the same in both hemispheres as 

 at present, there must have been more difference 

 between winter and summer in the northern hemi- 



1 Through the precession of the equinoxes and the secular variation 

 of the position of the major axis of the earth's orbit. 



