426 THE CLIMATE OF THE PLEISTOCENE EPOCH. " [Aug. I9OI, 



the Asiatic anticyclone having moved eastvs^ard, and that of North 

 America southward, the low-pressure area then lay farther east, and 

 its longest axis ranged south-west and north-east : cold north-east- 

 erly winds from the Polar Sea consequently prevailed east of the- 

 Strait, and the thermometer fell to —19^ Fahr/ 



As the temporary climate of these regions now changes from day 

 to day under the influence of the winds, so under the more permanent 

 meteorological conditions set up by the existence, during both summer 

 and winter, of the JN^orth American ice-sheet, permanent changes of 

 climate in these regions might equally have resulted. If a tongue- 

 shaped area of low pressure similar to that which now extends 

 statistically in January (fig. 17, p. 450) from Labrador to Nova 

 Zembla, but pointing in the opposite direction, had lain in winter 

 during the Pleistocene Epoch to the west of Behring Strait (as 

 shown hypothetically in fig. 18, p. 452), mild winds from the Pacific 

 would have then prevailed along the northern coast of Siberia. Under 

 such circumstances trees might have been able to withstand its winter 

 climate, as now at the North Cape on the same parallel of latitude. 



It may be pointed out that, under the conditions suggested ia 

 fig. 18, the climate of the area where the east-south-easterly winds 

 prevailed would have been milder than that farther south, on the 

 opposite side of the cyclonic centre, then subject to winds from 

 the north-west, for the same reason that the present climate of 

 Norway is warmer than that of Labrador. In connection with this 

 it is interesting to remember that it is along the Siberian coast,, 

 rather than farther inland, that the fossil remains of the mammoth 

 chiefly occur. 



The objection may be raised that the mammoth-bearing beds are 

 supposed to belong to a late stage of the Glacial Period, and not 

 to that of the maximum extension of the North American ice-sheet; 

 but it may be pointed out that the peculiar meteorological conditions 

 of the Pleistocene Epoch might have continued in the north-west of 

 the American continent even after much of the ice had disappeared 

 from regions to the south and east. 



The efi'ect upon the barometric pressure of a comparative^ thin 

 covering of snow and ice, if permanent, would be, in one sense, 

 similar to that of an ice-sheet many thousands of feet thick ; that 

 is to say, it would tend to cause conditions anticy clonic as 

 compared with those of the warmer adjoining regions upon which 

 no snow rested. It must be remembered that the direction of the 

 winds depends upon the alignment of the isobars ; on the com- 

 parative, and not on the absolute, height of the barometer in 

 contiguous areas. The winter climate of a portion of North-western 



^ The climate of this region varies from day to day, in accordance with changes 

 of the wind. Thus 37° Fahr. was registered at the spot named on October iSth,. 

 1883, and 40° Fahr. on the 16th, the wind being from the south-south-east. On 

 the 25th of the same month, the cyclone having moved to the east of the Strait; 

 and the wind having changed to the north, the thermometer fell to 23° Fahr., 

 on the 28th to 21° Fahr., and on the 29th to 15° Fahr. On December 10th, it 

 dropped to —21° Fahr., but a few days later rose again, the wind being warmer ,^ 

 to 30° Fahr. on the 18th, and 32° Fahr. on the 19th. 



