CAUSES OF CLIMATAL CHANGE 395 



the power of geographical change in affecting chmatal change, 

 and the fact that such change has occurred at various geo- 

 logical periods, there are some, and especially those who take 

 extreme views as to the latest period of cold climate, who 

 doubt its sufficiency to account for all the phenomena ob- 

 served. It is instructive, however, to notice that some of 

 the ablest of these, in default of other probable causes, are 

 driven to fall back either on agencies of a wholly improbable 

 character, or to give up the problem as insoluble. Two recent 

 examples of this deserve citation. 



The late Dr. Newmayr, of Vienna, a veteran physical geo- 

 grapher, in an able discussion of the climates of past ages, 

 one of his last scientific papers, has fallen back on the hypo- 

 thesis of a change in the position of the poles.^ His failure 

 to account for ancient climates by other causes evidently, 

 however, depends on an inadequate conception of the effects 

 of geographical changes, along with serious misconceptions 

 as to the distribution of plants and the characters of vege- 

 tation at different periods. These points we shall have to 

 discuss in subsequent pages. 



In an address before the American Association, in 1886, 

 Dr. Chamberlain, one of the ablest American authorities on 

 the Glacial period, makes the following remarks as to the 

 causes of the Pleistocene cold : — 



"If we turn to the broader speculations respecting the 

 origin of the Glacial epoch, we find our wealth little increased. 

 We have on hand practically the same old stock of hypotheses, 

 all badly damaged by the deluge of recent facts. The earlier 

 theory of northern elevation has been rendered practically 

 valueless; and the various astronomical hypotheses seem to 

 be the worse for the increased knowledge of the distribution 

 of the ancient ice sheet. Even the ingenious theory of Croll 



* Society for Dissemination of Natural Science. Vienna, January, 1889. 



