1910.] DAVIS— ANTARCTIC GEOLOGY. 201 



continental deposits is greatly favored by large continental area ; 

 and conversely, large continental area may be inferred from an 

 abundance of continental deposits ; thus the problem of polar cli- 

 mates is linked with the equally interesting problem of the changes 

 in land and sea areas through geological time. 



There is an important theoretical matter to be mentioned in this 

 connection. It will be remembered that Professor T. C. Cham- 

 berlin presented a communication at one of the April meetings of 

 this society several years ago, in which he suggested that a mild 

 polar climate might be caused by a reversal of the deep oceanic 

 circulation, whereby the warm surface waters of the torrid belt 

 would sink, creep along the bottom toward either pole, and rise in 

 high latitudes, where their warmth would determine a climate very 

 much milder than that of today. Evidently if this or any other 

 process that is capable of producing a mild polar climate has been 

 in operation at one time in the past, it may have been in operation 

 at various other times ; and thus a question rises to which Mr. 

 Bailey Willis drew attention in his address before the geological 

 section of the American Association at the Boston meeting of last 

 winter; namely, what has been the prevailing climate of the polar 

 regions through the geological ages? Naturally we open this 

 inquiry with a predisposition to regard the climate now prevailing in 

 high latitudes as the normal climate ; but if it once be shown that 

 a mild climate has sometimes prevailed there, it is entirely possible 

 that a mild climate and not the rigorous climate of today really 

 represents the prevalent conditions of the polar regions through 

 geological time. Under Chamberlin's theory of mild polar climate, 

 rain would be abundant but mud cracks would be rare ; hence even 

 so small a detail as the relative proportion of these minute struc- 

 tures in continental formations of high latitudes would have its 

 significance. Marine formations will probably give less decisive evi- 

 dence in this respect than continental formations ; but marine for- 

 mations would also have their importance, not only by reason of the 

 fossils they might contain, but perhaps even more from the pres- 

 ence or absence of scattered boulders and gravels, such as might be 

 dropped on a sea floor from floating icebergs. The prevailing 

 absence of such intermixture of floated materials in the marine for- 



