4.')4 S. S. VISIIKR— SAJJNITY AS CAUSE OF CLIMATIC CONTRASTS 



matter vvliicli bad accumulated iji tlie soil and sul).soil on the lands whoii 

 they were only slightly above sealevel. If widespread glaciation should 

 accompany or follow extensive uplift, as it did in tlie Proterozoie, Per- 

 mian, and Pleistocene, the rate at wbieJi salts were added to the bceaii 

 would be increased by both these agencies at about the same time. While 

 uplift and glaciation Avere increasing the amount of mineral mattt'i- 

 brought to the ocean in solution by the rivers, the rate of withdrawal of 

 mineral matter from solution would probably be lessened. At present 

 the calcareous and siliceous materials, which form a large part of the 

 mineral matter carried to the sea by the rivers, but only a minor part of 

 what is generally called the salines of the ocean, are rather promptly 

 removed from solution, perhaps chiefly through the activity of the marine 

 animals and plants, which use these minerals for their shells and supports. 

 Eestriction of the area of the continental shelf accompanying conti- 

 nental emergence and the accumulation of extensive ice-caps would doubt- 

 less greatly reduce the number and average size of shell-secreting marine 

 organisms, for most of them live in shallow water, on the continental 

 shelf. Furthermore, the lower coastal temperatures accompanying gla- 

 ciation would probably make the remaining animals less active in shell 

 formation. If so, lessened Avithdrawal of salts would cooperate with an 

 increased supply to cause the salinity of the ocean to increase rapidly 

 during glacial periods. 



Possibilities of a reversal in Direction of the nEEP-SKA 

 Circulation 



Under the conditions set forth in the preceding paragraph, and perhaps 

 under certain others, the salinity of the ocean as a whole, or of its warmer 

 portions, may have been temporarily greater than now, and thus the more 

 saline warm water of the dry tropics would become more dense than the 

 colder but less saline waters of subpolar latitudes. If so, the reversal in 

 direction of the deep-sea circulation suggested by Chamberlin^ may have 

 occurred. One result of such a reversal would be that lands in the higher 

 latitudes would be warmed much more effectively by winds blowing from 

 the sea than before the reversal took place. If such a reversal was ln'0U2:ht 

 about by the consequences of uplift and glaciation, described in the fore- 

 going paragraph, conditions for continued glaciation would seemingly be 

 made less favorable. Indeed, a reversal might bring the glaciation to a 

 close. 



"^ T. C. Cliambei-lin : On a possible reversal of the deep-sea circulation. .Tom. of Oeol- 

 ogy, vol. 14, 1906, pp. 3QS-RTA. 



