508 THE TROPICAL WOKLD. 



From the savannas and serai-deserts of the Tropical World, we now turn to the 

 great deserts themselves, which constitute a striking feature in that portion of the 

 globe which is now under review. A desert, in the strict sense in which we use the 

 term, is an extensive region wherein there is no regular rainfall, and in which, more- 

 over, there exists no other means of irrigation. It is a land doomed to irremediable 

 sterility ; for, as we have again and again pointed out, water is the great requisite to 

 life. We have taken Southern Africa, and even the Kalahari, out of the category of 

 deserts, because during a part of the year rain falls there, and therefore vegetable life, 

 and by consequence, animal life, may exist, and often does exist in great profusion. 

 The Valley of the Nile, including all Egypt, is rainless, and would be a desert, were it 

 not that the lower course of the river, supplied from rainy regions, overflows its banks, 

 and for the rest of the year it is irrigated by waters raised by human labor from the 

 abounding river. Egypt is the " gift of the Nile," and is redeemed from barrenness 

 by being, as described by the great Hebrew lawgiver, a land "watered by the foot." 



In America the only great tropical desert is that of Atacama, the " sand-coast of 

 Peru." It is a long, narrow strip of land lying between the parallels of 3 and 21 

 south latitude, bounded on the west by the Pacific Ocean, and on the east by the Cor- 

 dilleras. Its length is 1,600 miles, its breadth from 15 to 60 miles. It is traversed 

 by spurs from the mighty mountain range, which sometimes sink into the level of the 

 plain, and sometimes jut out in steep promontories into the ocean. Here and there, 

 at wide intervals, a brook fed from the snowy Andes, makes a brief course across the 

 narrow plain, forming a narrow strip of verdure only sufficient to break the general 

 monotony. The few inhabitants carefully husband the last drop of water from these 

 scanty streams to irrigate their arid fields. Here the mule takes the place of the Afri- 

 can camel as the " ship of the desert." The horse can not support thirst for more 

 than forty-eight hours without becoming so weak as to be scarcely able to carry its 

 rider ; yet if urged by his master he will stagger on until he falls dead in his tracks. 

 The mule, more obstinate, as we say, but in fact more wise, when he feels himself 

 verging upon the limits of endurance, stops short, and no urgency of whip or spur 

 will force him to move, until he has rested. Yet notwithstanding the great power of 

 endurance of the mules, many of them succumb to the fatigue of the journey, and the 

 roads across the Atacama are marked by their skulls and bones, as the caravan routes 

 across Sahara are whitened by the skeletons of camels. 



Perhaps the most absolute desert tract on the face of the globe is that which occu- 

 pies the interior of the great island, or, as it may not improperly be styled, continent, 

 of Australia. The island has an area of something more than three millions of square 

 miles, nearly equal in extent to Europe. For a great part of its circumference it is 

 bounded by a continuous range of mountains or highlands, nowhere rising to a great 

 hight, and for long distances consisting of plateaus or table-lands. There is, however, 

 a continuous range of water-shed, which is never broken through, and which never 

 recedes to any great distance from the coast. The habitable portions of Australia are 

 limited to the slopes of the mountains and the narrow space between them and the 

 coast, in all not exceeding a width of three hundred miles. The interior, as far as is 

 known, or as can be inferred from physical geography, 'is an immense depressed plain, 

 more hopelessly barren and uninhabitable than the great desert of Sahara. 



