THE GLACIAL HYPOTHESIS 321 



striated the whole surface. The glacial theory of Agassiz and others 

 he described as having grown, until, like the imaginary glaciers them- 

 selves, it overspread the whole earth. He adopted, rather, what he 

 called the moderate view of Sir Roderick Murchison and Sir Charles 

 Lyell to the effect that Pleistocene subsidence and refrigeration pro- 

 duced a state of our continents in which the lower levels, and at certain 

 periods even the tops of the higher hills, were submerged under water 

 filled every season with heavy field ice formed on the surface of the sea, 

 as at present in Smith's Sound, and also with abundant icebergs 

 derived from glaciers descending from unsubmerged mountain dis- 

 tricts. The later Pliocene, so far as Canada was concerned, he con- 

 sidered to be a period of continental elevation and probably of tem- 

 perate climate. 



Thus far the discussion relating to the ice period has been limited 

 wholly to workers and areas east of the Mississippi River. In 1880 

 and 1882 J. D. Whitney, one time state geologist of California, issued 

 his well-known work on climatic changes of later geological time, in 

 which he discussed the occurrence of glaciers and their possible 

 origin in the west, particularly in the region of the Great Basin. 

 Whitney thought to be able to trace a period of warmth and heavy 

 precipitation, followed by one of desiccation, but anticipated by one 

 of cold and glaciation, the glaciers, however, being limited to the most 

 elevated ranges of the Cordilleras. At the outset he announced him- 

 self as opposed to the ' wild and absurd ideas ' that had prevailed re- 

 garding glaciation in the Sierras, and stated it as his belief that here, 

 at least, ice had played but an extremely subordinate part as a glacial 

 agent, though ' there is no doubt but that the great California range 

 was once covered with grand glaciers, but little if at all inferior to 

 those which now lend such a charm to the Swiss Alps.' 



It was Whitney's opinion, further, that the geological importance 

 of the ice sheet had been greatly exaggerated. It seemed to him be- 

 yond question that icebergs had played an important part in carrying 

 and distributing the large angular boulders which in many places rest 

 upon the surface in such a manner as to show that they could not have 

 been placed in their present position by running water or by a general 

 ice sheet. 



He regarded it as evident enough that the climate of northeastern 

 America during the glacial epoch was a period of greater precipitation 

 than now, but that it was a period of intense cold he would not admit. 

 Glaciation or a glacial period was due merely to increased precipitation. 

 In order that such precipitation should take place, an increased evap- 

 oration from the land and water was necessary. This could be brought 

 about only by a general increase of temperature. The amount of pre- 

 cipitation being sufficient, the production of glaciers would depend 



vol. Lxvin. — 21. 



