202 



MAP KEPEESENTING- NOETH AND SOUTH 



[Ch. XII. 





* 



mi 



cal change as having occurred in an interval sufficient to 

 allow of fluctuations in organic life on so much grander a 

 scale. Even if changes in the position of land and sea are 

 brought about as slowly as those now in progress, so as to 

 be quite insensible to ordinary observation, we may still be 

 prepared to believe that when we go back to the older Pliocene 

 period, land between the arctic and antarctic circles and the 

 pole may have been so much less in quantity as compared to 

 what it now is, that instead of being equal in area to the 

 sea, it may only have been in the proportion of about 1 to 



But such a reduction of the quantity of land in high 

 latitudes would be accompanied by an equivalent increase 

 of land in temperate or tropical regions, unless we suppose 

 the general surface of the earth's crust to have been less 

 irregular than it is now — an hypothesis which we are not 

 entitled to make. Consequently, whatever is lost to polar 



areas, where land gives rise to an augmentation of cold, 



01 



would be gained in those lower latitudes, where it causes 

 an increase of warmth. Therefore a more normal state of 

 geography, or one in which the polar, temperate, and equa- 

 torial regions would each contain more nearly than they do 

 now a proportion of one part land to two and a half parts 

 ea, would bring back those genial climates which generally 

 obtained in the past history of the world. 



The accompanying map (fig. 13) may help the reader to 

 imagine what would be the amount of change, if the 

 geography of the globe were altered from its present ex- 

 ceptional state to what I consider a more normal condition 

 of things. In this ideal map the excess of land is removed 

 from the arctic and antarctic zones, and tran 

 the tropical zone, which last, after this accession, contains 

 only its normal quantity of land, or a proportion to 

 the water of about 1 to 1\. The land thus shifted from the 

 poles has not been placed at random in the tropics, but has 

 been made to fill those oceanic spaces which are supposed to 

 have been above water in Post-tertiary, or at least, in Newer 

 Pliocene times, in accordance with Darwin's map of coral 

 atolls. It may be objected that during such an amount of 



to 



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