Vol. 57.] CLIMATE OF THE ^LEISTOCE^^E EPOCK. 465 



causes of those movements, Nevertheless, we know that any ira* 

 portant meteorological disturbance at one point, however produced, 

 may affect, in a greater or less degree, the atmospheric conditions 

 in regions far removed from it, so that the initiation of secular 

 movements of the Polar anticyclone during the Glacial Period may 

 have arisen at some distant point, or in some unsuspected manner/ 



It seems, however, that any permanent shifting of the Polar 

 anticyclone which may have taken place during the period in 

 question (possibly not of a more serious character than that which 

 occurs from time to time at present) must have followed rather 

 than have preceded the suggested transference of the ice from one 

 side of the Atlantic to the other. 



The existence of an ice-sheet in either hemisphere must have 

 produced more or less permanence in the climatic conditions of the 

 regions under its influence, so that changes in the relative position 

 of areas of high and low pressure would have been of a temporary 

 character, tending always to revert to the normal. It seems neces- 

 sary, therefore, to suppose that it was by the means of some outside 

 disturbing force that alterations in the position of the ice-sheet 

 were initiated. Unless that force were extra-telluric, or some such 

 as that suggested by Prof. Chamberlin (mentioned below), the 

 hypothesis which attributes climatic changes to tectonic movements 

 of subsidence and elevation, seems to offer the best explanation of 

 the difficulty. 



The view that the Pleistocene Epoch was one of epeirogenic dis- 

 turbance is held on both sides of the Atlantic. The late Prof. Le Conte 

 believed that the eastern part of the North American Continent 

 stood during the Ozarkian Period (already referred to) from 3,000 

 to 5,000 feet at least above its present level, and it is to this he 

 attributed the glaciation of that region.^ Prof. Chamberlin adopts 

 Le Conte's view, although he considers that the glacial refrigeration 

 was not so much due to this cause directly, as indirectly, through 

 its effect on the amount of carbon-dioxide in the atmosphere. 

 American geologists trace, moreover, at a later stage in the Glacial 

 history, that of the Champlain deposits, a great subsidence, affecting 

 principally the eastern and northern portions of the continent. The 

 apparent connection between glaciation and subsidence has also 

 been pointed out by Prof. .James Geikie,^ who has adduced many 

 cases of alterations in level during the Pleistocene Epoch. 



In both the New and the Old World, therefore, we have evidence 

 of upheaval on the one hand and subsidence on the other, during 

 various stages of the Glacial Period. We can in some measure 

 establish, locally, the sequence of these tectonic changes ; but there 

 may have been other oscillations of level, especially such as may 



^ Prof. Fairchild remarks: 'The various elements affecting climate, 

 geogi'aphic, atmoi«pheric, and astronomic, are thought to be so nicely balanced, 

 that a comparatively slight change or maladjustment may produce serious 

 climatic etfeots.' Proc. Araer. Assoc. Adv. Sci. vol. xlvii (IbUSj p. 271. 



^ Journ. Geol. Chicago, vol. vii (1899) pp. 527 ct stqq. 



3 ' Great Ice Age ' 3rd ed. (1894) pp. 6U15, 794, etc. 



