GEOLOGY — CHAMBERLIN. 1 85 



regions by virtue of which the carbon dioxide of the frozen layer as 

 well as the salts is forced out into the layer beneath and supercar- 

 bonates it, while the increased salinity aids in its descent and promotes 

 the profound circulation. 



In attempting to estimate the eflficiency of the polar agencies in 

 promoting this deep circulation and thus to reach some estimate of 

 its period, the fact was disclosed that the evaporation of the low lati- 

 tude belts of relatively dry descending atmosphere and of trade winds 

 caused an increase of specific gravit}' through increased salinity some- 

 what closely comparable to the increased density effected in the polar 

 regions by low temperature and freezing. Out of this arose the sug- 

 gestion that in those periods in which low temperatures and freezing 

 in the high latitudes were absent or limited, as indicated by the faunal 

 and floral record, their efficiency in increasing the density of the sea- 

 water might have been overbalanced by the increase of density due 

 to evaporation in the low latitudes, and that the dcep-sca circulation 

 of these periods 7riay have been the reverse of that of the cold periods, being 

 actuated by evaporation in the low latitudes. The data for developing 

 this suggestion into a firm conclusion are not at command and, with 

 the degree of study thus far given it, it can only be regarded as a 

 suggestion whose importance depends on its justification. It is at 

 once evident that if such deep-seated circulation from the Equator to 

 the poles were actually realized, the warmth of the polar regions in 

 such periods would cease to seem extraordinary, because the waters 

 -descending in the low latitudes with a subtropical temperature would 

 give to the whole abysmal mass of the ocean a corresponding tem- 

 perature, and would rise in the polar regions with little or no loss 

 of heat and give forth warm vapors which would enshroud the polar 

 regions during the protracted night and protect them from effective 

 low temperatures, while during the protracted day the temperatures 

 would be hospitable to subtropical life. 



This suggestion also furnishes a possible elucidation of the perio- 

 dicity of the glacial and interglacial epochs, for while a reversal of 

 the circulation can scarcely be postulated during the prevalence of 

 the general conditions which favored glaciation, a profound change 

 in the carbonation of the sea-waters and a correlated change in the 

 carbonation of the atmosphere is readily deducible from the deep-sea 

 circulation. This, however, is coordinated with other influential 

 conditions and with other assumptions which render the case too 

 complex for statement here. This sketch is merely intended to 

 indicate the lines of study and something of their applicability. 



