268 THE POPULAR SCIENCE MONTHLY 



Deserts of sand and deserts of snow: both alike repel man. Both 

 are largely or wholly destitute of vegetation, of wood and of water. 

 The yellow desolate waste of the sand desert is matched by the monot- 

 onous white surface of the snow desert. There are no opportunities for 

 accumulating wealth in either. Travel is difficult in both. In one, the 

 camel is the typical beast of burden ; in the other, the reindeer and the 

 clog are man's most useful possessions. The monotonous heat and 

 glare and silence of the sand desert find their counterpart in the cold, 

 and glare, and silence of the snow desert. The air is generally clear in 

 both, except for the dust over the sand desert and the ice-needles in the 

 air of the snow-desert. In both deserts, man is very limited in his 

 food supply : in the Sahara the date, in Greenland the seal, are typical 

 staple articles of diet. The aridity in one, and the cold in the other, are 

 man's great enemies. The inhabitants of both deserts are nomadic. 

 Settlements of some permanency are found in oases or along the edges 

 of the sand desert, where there is water; similarly, the natives of the 

 far north live along the edges of the ice desert, where they can best 

 find their food. The sand deserts are deserts because they are arid. 

 The snow deserts are deserts because they are cold. Denudation of 

 exposed rocks in the desert of sand is largely due to the action of wind, 

 carrying sand; and denudation of the surfaces of ice in the desert of 

 snow is due to the action of wind carrying ice spicules. The polar 

 deserts are perhaps on the whole better suited to life than the sand 

 deserts, for the former supply water from the melted snow and ice. 

 Man has, however, a harder struggle to protect himself against the 

 cold than against the heat, for he needs more clothing, and better 

 shelter, and fire. In both deserts life is isolated and primitive. The 

 sand desert is crossed by caravans and trade routes between the more 

 populous lands on either side, and the people of these deserts have more 

 contact with civilization than do most of the natives of the far north. 

 The polar desert of snow and ice : who travels across it except the oc- 

 casional explorer, seeking the Pole? 



