THE GREAT AUSTRALIAN DESERT. 509 



The interior of this desert has probably never been traversed by the foot of man or 

 beast; and only three or four exploring expeditions have penetrated far into its depths, 

 In 1844 Sturt made his way some four hundred miles beyond the habitable regions, 

 which brought him near the geographical center of the island. This space he found 

 to be occupied by an immense plain covered with ridges of drifting sand, often rising 

 to a hight of eighty or a hundred feet, and stretching away in either direction beyond 

 the range of vision. Here and there grew a few solitary tufts of grass, nourished by 

 infrequent showers. Permanent water there was none, and the sand was heated to 

 such a degree that a match dropped upon it became ignited at once. The thermometer 

 on one occasion rose to 153 in the coolest place to be found. In the midst of this 

 sterile tract was a desert of still deeper gloom, which was traced for a distance of 

 eighty miles in one direction, and thirty-five in another. Its surface was paved by a 

 solid bed of dark iron-stone, upon which the horses' hoofs rung as upon a metallic 

 floor, without making the slightest indentation. There was not a trace of water or 

 vegetation. Leichardt, a German naturalist, succeeded in penetrating from the settle- 

 ments on the eastern coast, through the unexplored interior of the island, to its northern 

 side. But his course led him only along the skirts of the great desert ; yet even here 

 he was more than once saved from perishing by following the flight of a bird winging 

 its way to some solitary sink or water-hole. In 1846 he set out on a new journey, 

 intending to pass from the east through the desert to the colony on the western shore. 

 This journey was expected to occupy two and a half years. Eighteen months after he 

 set out, a letter was received from him written on the extreme verge of habitation. 

 After that he disappeared, and it was not until years after that it was discovered that 

 he had been murdered by his native guides. 



When it was ascertained that no rivers from the interior reached the sea-coast, while 

 considerable streams poured from the hills towards the interior, it was supposed that 

 there must be a great central lake. Sturt followed the Victoria, the most consider- 

 able of these rivers, which poured a considerable current into the interior; but the 

 farther he followed it the less became the stream, which at length dwindled into a 

 succession of water-holes, and was finally lost among the barren sands. It is probable 

 that the same is the case with all the streams running into the interior ; and that all 

 their water is exhausted by evaporation long before the center of the island is reached. 



But the great desert of the Tropical World is the African Sahara, occupying the 

 central portion of the northern half of the continent from the latitude 17 to that of 

 29, although in many parts fruitful districts penetrate its bounds like peninsulas 

 jutting into the sea. No European traveler has followed its southern limits from east 

 to west; and of its interior little is known, except along the caravan routes traced 

 across it for centuries. One scarcely strikes the northern border of the Sahara before 

 he finds himself in a region beset with perils. 



The first portion, after leaving Tripoli, following the caravan route, known as the 

 Hamada, is an elevated plateau, six days' journey wide, barren and stony, except 

 here and there where there is a patch of verdure upon which the patient camel browses 

 with delight. Here is found a little bird called the asfir, which lives wholly upon the 

 vermin which it picks from the feet of the camels. Then comes a broad, sandy, tree- 

 less plain, crossed by shifting sand-ridges so steep that the traveler is often obliged to 



