CLIMATIC VAEIATIONS GREGORY. 345 



Jurassic. The British Cretaceous marine deposits indicate the prev- 

 alence of a cool temperate, and those of Greenland an arctic, climate, 

 in the period when, on the unreliable evidence of fossil leaves, we are 

 asked to believe the conditions in Greenland were tropical or sub- 

 tropical. 



The paleontological evidence at present available does not throw 

 on us the burden of explaining why the Arctic had a tropical cli- 

 mate, for it simply contradicts assertion as a matter of fact. 



Glaciation Due to Local Climatic Variations. 



The second line of evidence used to prove intense, widespread 

 climatic changes is the occurrence of glacial deposits in the temperate 

 zones and the greater extensions of tropical glaciers. But this evi- 

 dence has also been used to indicate more extreme changes than are 

 necessary to explain the facts. Thus, it appears to be sometimes con- 

 sidered that the glacial beds of South Africa, India, and Australia 

 prove that in one epoch of the Upper Paleozoic the whole area of 

 the Indian Ocean, from 30° N. latitude in India to more than 40° S. 

 in Tasmania was undergoing glaciation. 



The difficulty of explaining former glaciations has been greatly 

 increased by such assumptions as that they were due to the develop- 

 ment of a severer climate at the same time throughout the world. 



There is not yet adequate evidence that the former glaciations were 

 accompanied by a universal change of climate. It is true that there 

 is evidence of a more extensive Pleistocene glaciation in many regions 

 of the world, including Mount Kenya, upon the equator in British 

 East Africa, Mount Kosciusko in southeastern Australia, western 

 Tasmania, the South Island of New Zealand, Patagonia, and a belt 

 practically all across the temperate regions of the Northern Hemi- 

 sphere. Accordingly it is claimed, as b}^ Ekholm (op. cit., p. 34), 

 that the snow line was everywhere 1,000 meters lower at the time 

 when Europe had its " Great Ice Age." But there are too many 

 cases in which evidence of such former extension has been sought for 

 in vain, for a universal lowering of temperature in the Pleistocene 

 to be accepted as yet finally established. In the North Island of New 

 Zealand there is no evidence of any former glaciation, and had its 

 existing snowfields extended more than 3,000 feet lower, they should 

 have left some traces of so great growth. D'Orbigny and Whymper 

 both failed to find any evidence of any greater extension of the exist- 

 ing glaciers on the equatorial Andes than could be explained by a 

 local variation in the winds. In equatorial Africa no Pleistocene 

 glacial deposits have been found, except on the dwindling summits 

 of the highest mountains; and the coastal raised beaches give no 

 evidence of any contemporary reduction in the temperature of the 



