HVPOTHESIS OF CAUSE OF GLACIAL PERIODS 763 
cross Greenland from the east and northeast. The nature of 
the circulation ts such that Greenland 1s really on the leeward side of 
the north Atlantic. This is shown by the following tables of pre- 
vailing winds. The first is from the prolonged observations 
recorded at Godthaab and Upernivik, by Dr. Rink; the second, 
from those taken under the direction of General Greeley at Fort 
Conger in the years 1882 and 1883: 
PERCENTAGES OF TIME DURING WHICH GREENLAND WINDS BLOW 
FROM THE DIRECTIONS NAMED 
At Upernivik At Godthaab 
Lat. 72° 47’. Long. 55° 35’ Dat, 64° 2x". “Long, 51.43" 
Direction Winter Spring | Summer | Autumn Winter Spring | Summer | Autumn 
ING ereistia or 25.5 33.9 31.9 28.8 B21 37.4 30.3 25.5 
ID eesactetewead 34.3 2251 16.2 36.5 38.4 24.8 8.6 33.6 
Shear tresctacel| Lige5 20.3 28.0 18.1 16.1 ey) 32.9 22.9 
Was) cess wns 1.8 2:5 6.4 4.4 4.9 5.7 15.1 6.2 
Calms). ..2: 22.9 20.2 1725 12.2 7.5 10.4 eel 11.8 
100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 
FREQUENCY AND VELOCITY OF WINDS AT FORT CONGER, 
LAT. 80° 44’ N., LONG. 64° 45’ w. 
1881-2 1882-3 
Direction 
Times Miles Times Miles 
IND epefet oekestrcnnkerestesetsnaa ees 303% 1522 420 2401 
Ni Ete Latent cst avs laces 761 3061 1022 4613 
NEP ein, etersea ie ea ta hrscen ovate hays I151% 4843 1369 4061 
S aE toners ees aave ree 67814 3605% 862 3650 
DORs eesti Oa mah cnet acta ™uleielels 683% 386414 775 4214 
Sr Wisi tee sie penten ait at sveaae ails tes 678 2011 goo 3059 
AV iWeeneek te etree cng teaver eaa 371 949 343 997 
INEM icite, cay teaiofoisetenadare. Cat ns 206 720 387 1142 
alma eens, eh cer tan fone capstan Gistenecs 3408 1282 26082 50 
The winds of the summer months are much influenced by 
local features, especially by the sea, the naked earth and the ice 
fields, respectively, while in the cold months a nearly uniform 
mantle of snow or ice covers the whole surface in common, and 
removes essentially all sources of variation except those of 
