16 AGRICULTURAL EXPLORATIONS IN ALGERIA. 



Babors groups, which border this part of the region, reach altitudes 

 of 7,000 feet. 



A marked feature of the steppe region is the frequently occurring 

 •*da3'as" and "chotts" — salt ponds or lakes without outlet — which 

 receive the drainag'e from the southern slopes of the coast mountains 

 and the northern declivities of the Saharan range. They occupy basin- 

 like depressions, and are often dry or merel}^ marshy in summer, their 

 beds being then covered with a shining crust of salt. The "bolson" 

 plains of the Sonoran region in North America have a similar hydrog- 

 raphy. 



There is very little water in the high plateau region suitable for 

 drinking or for the irrigation of crops. Occasional wells occur, and 

 here and there are small pools where sheep and cattle drink. As a 

 rule, however, travelers in this region must carr}' with them their sup- 

 ply of drinking water. Attempts to find artesian water have generally 

 been unsuccessful. 



In places the topograph}" of the steppe region becomes almost iden- 

 tical Avith that of the desert — notably where areas of sand dunes occur 

 and the vegetation is very scanty. Such localities difl'er from the 

 desert proper only in their greater elevation and more severe winter 

 climate. 



DESERT REGION. 



A considerable portion of the largest desert in the world, the Sahara, 

 lies within the boundaries of Algeria. Contrary to the general notion, 

 the mean elevation of this desert above sea level is considerable, being 

 placed by some authorities as high as 1,540 feet. Broadl}^ speaking, 

 the surface of the desert is convex, the central portion being generall}^ 

 higher than the borders. The desert is conmionly pictured as a vast 

 billowy expanse of sand blown about b}^ the sirocco and dotted with 

 oases. This conception is only partly true. As a matter of fact, the 

 topography of the Sahara is as diversified as that of most areas of equal 

 extent in other parts of the world. In this respect it is to be com- 

 pared with the desert regions of the southwestern part of the United 

 States. The Sahara contains mountains nearly 7,000 feet high, upon 

 whose sunmiits snow remains throughout the winter. Other parts are 

 consideraV)ly below sea level. Much of its surface is broken by ranges 

 of sand dunes and of rocky hills, between which lie narrow ravines or 

 wide valle3's. In other quarters extensive plateaus occur. The courses 

 of streams that must once have carried a considerable volume of water 

 can be traced in many places. The infrequent rains that fall in the 

 Sahara sometimes fill the bottoms of these channels with water for a 

 few brief hours. But even such transient torrents can effect a tre- 

 mendous amount of erosion in the loose soils of the desert, there being 

 little vegetation to hold them in place. Lakes and ponds are iiumer- 



