406 ON THE GLACIAL CLIMATE AND THE POLAE ICE-CAP. 



not act during the glaciation of the southern hemisphere, because, 

 in consequence of the totally different disposition of the land, there 

 are not in that hemisphere any great poleward currents. 



My theory of the glacial climate, however, does not come into 

 collision with Mr. Croll's on the subject of ocean currents, because 

 the effect on climate of any change in the currents will be the same 

 in kind, whether glaciation is caused by an aphelion winter or an 

 aphelion summer. Such a change in the currents as Mr. Croll 

 supposes cannot begin to act on climate until a change of climate 

 has first begun to divert the currents. I think, however, that the 

 cold of an aphelion summer at maximum eccentricity will amply 

 account for the glacial climate by its direct effect, without any agency 

 of ocean currents being needed. 



