1896.] On the Recurrence of Ice Ages. 110 



deep was now filled with solid minerals 1\ times the specific 

 gravity of water — all of which had been transferred from an 

 adjoining continent 20,000 feet high ? 



In this connection how suggestive is the fact that "all the 

 extreme depths in the ocean are near land or shallow water, and 

 apparently follow the trend of such upheaved parts of the earth's 

 crust 1 ." 



It is also worth noting that the deepest depressions yet found 

 in the ocean, namely, between 30,132 feet and 30,930 feet, were 

 those proved by Captain Balfour about 500 miles N.E. of New 

 Zealand along approximately the same belt of latitude as that of 

 the depression containing glacial deposits in South-eastern 

 Australia. 



If regional movements depend upon terrestrial causes such as 

 denudation and deposition, and if shrinkage of the nucleus and 

 astronomical causes determine only the time when the necessary 

 readjustments shall take effect, it is clear that the general con- 

 tinuity and never the permanence of oceanic and continental 

 areas must follow as a matter of course. Migration along the 

 growing land leaves at the end of a long period a record of similar 

 fauna and flora, continuous, but not contemporaneous. Hence the 

 difficulty of assigning an exact date to the deposits containing the 

 wide-spread Glossopteris and Gangamopteris. 



Here we have at last exact observations on an ancient glacial 

 deposit occurring in a region where the conditions are now such 

 that no glaciation is possible, and we find that no glaciation took 

 place in that area on the former occasion either, but only that 

 glaciated stones were carried there. 



We have evidence of great earth movements such as would 

 account for all the phenomena over the whole of that region, even 

 down to recent times. 



It would be well if astronomers and physicists would cease 

 to consider only the view that the different amount of heat 

 received from the sun alternately in either hemisphere is 

 sufficient to account for the variations of climate which have been 

 experienced by different regions. They are not asked to account 

 for any deformation of the whole mass of the earth, nor for any 

 violent dragging of the topographical poles from the ends of the 

 axis of rotation. What they are now asked to consider is, whether 

 there are no forces which have a tendency to distort and dislocate 

 portions of the surface of the crust ; forces which shall be always 

 tending towards a readjustment of equilibrium over those regions 

 where transference of vast masses of material from one area to 

 another has deranged it; which shall have some tendency to 



1 Wharton, W. I. L. Nature, Vol. 53, Feb. 27, 1896, p. 393. 



