THE TUNDRA AND ITS FAUNA 17 
The precipitation is everywhere small, except in the 
south-western extremity of Greenland. Elsewhere the 
mean never exceeds 10’ per annum, and may be much 
less. The winters especially are remarkable for the 
clearness and dryness of the atmosphere and the 
virtual absence of precipitation. The result is that, 
contrary to what might be expected, the snow does not 
form everywhere a thick mantle, and the frequency of 
strong winds helps to diminish its thickness in places, 
a fact which greatly aids the obtaining of food by 
such herbivorous mammals as the reindeer and musk- 
ox. During the short summer precipitation is frequent, 
though slight, and fog and mist are common. The sub- 
soil is permanently frozen, and there is thus no ground 
water. This renders all erosion mechanical, and as 
springs are absent the rivers are fed only by the melt- 
ing of ice and snow, and are temporary, being frost- 
bound in winter. 
There are only two seasons—winter and summer— 
and the winter extends far into the months which are 
spring elsewhere, so that March or even April may be 
the coldest month. It is apparently these months which 
take the largest toll of animal life, for Nordenskidld 
notes that the reindeer are in better condition in the 
depth of winter than in the spring months. Summer 
comes with extraordinary rapidity, and with its coming 
life suddenly bursts into activity. Thus all the flowers 
bloom at once, giving rise to the local luxuriance 
noticed by many explorers. The rapidity of develop- 
ment is of course aided by the virtually continuous 
daylight. As the rays of sunlight have a very oblique 
direction, local conditions count for much in promoting 
the growth of plants, and therefore the occurrence of 
land animals. Thus a slope where the ice-cold water 
1404 B 
