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 monotonous 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 occasional explorer, seeking the Pole?
