1875.] 337 [Shaler. 



pole and their apices towards the southern, a small difference in the 

 altitude of the regions about the north pole must have made a very 

 oreat difference in the penetration of warm water, and the escape cf 

 cold water and ice from that region, and thereby profoundly affected 

 its climate. 



2d. That the elevation and depression due to glacial action 1 must 

 tend frequently to open and close these barriers; and that we have in 

 these necessary accidents a means of accounting for the occurrence 

 from time to time of warm periods which the geological record shows 

 to have existed. 



3d. That the destruction of this barrier and the consequent ad- 

 mission of the Japan current into the Arctic Sea, must tend to bring 

 up the average temperature of Europe and North America, and must 

 have a very great tendency to make the winter temperature less rig- 

 orous. Therefore it may be considered a possible cause of the 

 warm climate shown to have existed in Europe during various peri- 

 ods of Cenozoic time. The sudden alternations from cold to warmth 

 becomes thus explicable, being accounted for by the fact that the ac- 

 cumulation of ice brings about the subsidence that opens the way to 

 the tropical currents toward the poles. 



4th. That the opening and closing of this barrier must have some 

 effect upon the distribution of the cold polar waters over the depths 

 of the sea floor. 



5th. The passage of any considerable part of the Japan current 

 into the Arctic Circle would necessarily not only elevate the temper- 

 ature of the circumpolar region, but would also lower the equatorial 

 temperature by a proportionate amount. It is not easy to determine 

 the change of temperature in either case, but for the elevation of the 

 inter- Arctic regions by the amount of twenty degrees in the mean 

 annual, the mean temperature at the equator would probably be 

 lowered by at least one fourth that amount. 2 



1 For a theory of the nature of the forces involved in the production of the de- 

 pression occuring during the glacial period, the reader is referred to a paper by the 

 author of this notice, in the Memoirs of the Bost. Soc. Nat. Hist., Vol. n, Part in, 

 No. 3, page 335, 1874. 



2 As this paper goes to press, I find in the 4th edition of Dana's Manual of 

 Geology a reference to an opinion of Mr. Bradley, who, it appears, has already 

 called attention to the effect of lowering the Alaskan barrier on polar temper- 

 ature. 



PROCEEDINGS B. S. K.- H. — VOL,. XVIIi 22 APRIL, 1875, 



