THE POSITION OF THE EARTh's AXIS. 125 



of the Pliocene a great portion of the same area was covered; 

 and it was only in this period that most of Italy became 

 land. And then came the ice-age, when the ice must have 

 increased gradually, and the glaciers grew until those from 

 England and Scotland covered a considerable part of Bri- 

 tain and joined those from Scandinavia, and, as all know, 

 the glaciers of the mountain regions of Europe, Asia, and 

 America had such great extensions. During this and the 

 interglacial period elevations and subsidences (or kindred 

 phenomena) were brought about, in some places amounting 

 together to not less than four thousand feet. 



It would be almost impossible to conceive that the changes 

 since the Eocene were all accomplished in a million years ; 

 that would seem a short time for such alterations, which 

 have taken place since so recent a geological period. But 

 geologists must not claim more than a minimum ; for Sir 

 William Thomson a few years ago pulled up some rather 

 sharply for going too fast, and making too great calls upon 

 time, which it had become rather the custom to look upon 

 as unlimited. By various methods it was indicated that 

 the time to be allowed for life on the earth could not have 

 been more than about lOO million years. The only argu- 

 ment which now remains is that which limits the age of the 

 sun's heat, which must be definite when a complete know- 

 ledge is obtained of the method in which the heat was 

 generated. 



I have not entered into a consideration of the effect of 

 upheaval on the centre of gravity and the difference of con- 

 traction of the earth's crust by secular cooling under the 

 land- and water-areas, the production of which may be 

 influenced by the position of the earth's axis ; but I hope 

 some Member of this Society may take up these questions. 



The points I wish to bring forward are, that a change 

 of the position of the axis would elucidate many facts which 



