668 THE POPULAR SCIENCE MONTHLY. 



again become the home of a thriving population and the granary of 

 North Africa. 



To flood the shotts would require only the piercing of the isthmus 

 between El-Jei'id and the Gulf of Cabes. This is about thirteen miles 

 wide ; but Captain Roudaire thinks that the curve of altitude would 

 reach zero at about eleven miles from the Mediterranean, which would 

 materially reduce the amount of excavation. As the evaporation 

 would be much greater than in the Mediterranean, a large and con- 

 stant flow of water from the latter would be necessary to keep it at 

 its proper level. This would require a canal at least one hundred 

 yards wide, which could be constructed, it is calculated, at a cost of 

 twenty million francs. To this amount would have to be added a 

 sufiicient sum to compensate for the destruction of property in the 

 Tunisian part of the depression, which would ensue from its submer- 

 sion. Besides the towns of Nefta and Tozer, there are many douars, 

 or villages, in the oases, surrounded by cultivated lands and date plan- 

 tations. These are generally in the lowest part of the depression, for 

 there only can potable water be found, the higher land being without 

 springs. 



The superior council of Algeria, comprehending the immense ad- 

 vantages which would accrue to the colony from the consummation 

 of this scheme, voted in 1873 a sum sufficient to continue the survey, 

 and a well-appointed expedition, under command of Captain Roudaire, 

 made a thorough examination of the bed of the Algerian portion of 

 the shotts in the following year. The French Geographical Society, 

 taking a national as well as a scientific interest in the question, also 

 contributed money in furtherance of the object, and deputed M. Du- 

 verrier, one of its members, to accompany the party. The expedition 

 entered the depression on the northwest side of Shott Melrir. The 

 soil there is sand and marl, charged with salt. The many streams 

 which traverse the country have, with a few exceptions, no running 

 water, excepting in winter and spring, the season of rains and of the 

 melting of snow in the mountains. These rivers usually divide, before 

 reaching the shotts, into several branches, which again subdivide and 

 form innumerable ramifications. Where these begin to disappear, the 

 soil, which is charged with salt and almost bare, swells and cracks, 

 and the water sinks, when the crust reforms. Farther east are naked 

 plains of marl, level and smooth, and covered with a white incrusta- 

 tion wliich produces frequent mirages. On the extreme west the river 

 beds enter Shott Melrir with separating. On the south side are sand 

 hills and moving sands. 



All the shotts are alike in general features. All have flat bottoms 

 with an inclination too slight to be perceptible to the eye, and all form 

 basins which receive water-courses. The soil of all contains a great 

 quantity of salt, which whitens their bed in dry places. But each has 

 its peculiarities. The west end of Melrir has a bottom of sandy earth, 



