ARGUMENT FROM CLIMATE 269 



existence of a similar climate in the southern hemisphere, 

 and there are not wanting indications to show that a fall 

 of temperature has at no distant date affected tropical 

 Africa under the equator. Is it likely that this cold 

 climate wandered about the earth, paying flying visits to 

 one country after another in turn ? Are not the chances 

 many times greater that it was universal and affected 

 simultaneously the whole globe ? An affirmative answer 

 to the latter question may be fortified by independent 

 evidence, and carries with it the precise contemporaneity 

 of the Pleistocene glacial deposits. It would not, how- 

 ever, be given altogether unanimously, for an opinion has 

 been expressed that the climatal conditions of the glacial 



<Kif<xei. /fiocen*. Pliocene. Pleistocene 



for JSriftsk fetes during Ite Ttftwuy A.erof. 



FIG. 83. 



period passed rhythmically to and fro between Europe and 

 America, and even oscillated across the equator between 

 the northern and southern hemispheres. But even on this 

 view the contemporaneity of the Pleistocene series as a 

 whole is not necessarily denied; all that is denied is the 

 contemporaneity of individual beds, which, as it has not 

 yet been asserted, and forms no part of existing geological 

 doctrine, is for our argument of no consequence. 



A similar argument may be applied to the evidence 

 afforded by the Tertiary systems which lie below the 

 Pleistocene. In proportion as we descend lower in this 

 series, we encounter both in America and Europe signs of 

 a progressive amelioration of climate (Fig. 83) ; glacial con- 



