534 THE POPULAR SCIENCE MONTHLY. 



as these, in all probability came from the Nile, and as the sand exca- 

 vated from those wells is much the same as that of the Algerian bor- 

 ings, it is supposed that in both cases the fish infiltrate through with 

 the water to the subterranean sheets. 



It must not be supposed that, once the wells are dug, all labor is at 

 an end. M. Charles Grad, who visited the region in January, 1872, 

 found that several had ceased flowing, and that the greater part had a 

 less issue. A few, on the other hand, he found yielded a greater vol- 

 ume than at first. He studied the matter, as did also M. Ludovic 

 Ville, Directeur des Mines d'Algerie. The causes of the lessening of 

 the flow were found to be the crashing-in of the tubes, the accumula- 

 tion of sand in them, and the increase in the number of the wells, 

 which caused too great a drain on the reservoirs. The life of the wells 

 there without repairs seems to be twenty-five years ; some have been 

 known to last eighty without being cleaned. 



The lesson to be drawn from this is expressed by the old saying, 

 " Waste not, want not." Wherever it is possible to dam up the run- 

 ning streams of winter and make a reservoir for the summer, it should 

 be done, and artesian borings made where such streams are not avail- 

 able. Among other places, M. Grad maintained that the fertile basin 

 of the Hodna, situated on the Algerian jjlateau, would be the scene of 

 that kind of work. These dams have already been extensively built 

 in the province of Oran. 



In the Sahara, however, the absence of superficial streams renders 

 artesian borings of paramount importance. They will be limited there 

 not only by the underground supply, but in some places by the hostil- 

 ity of the nomadic tribes who oppose their immediate construction. 

 To what extent they can be relied on to reclaim desert-land is still an 

 open question, but at the very least they can be permanently distrib- 

 uted along the routes of caravans that penetrate into the southern 

 solitude, and with palm-trees planted about them form shady resting- 

 places. Up to 1872 one hundred and fifty thousand palms had been 

 planted in the vicinity of the many wells dug in Algeria ; in their 

 shade, after the salty ground had been well washed by the flow of 

 water, vegetables and grain were found to thrive. M. Ville, who has 

 made such a special study of the water of the Sahara, announces that, 

 as a rule, a well will water six times as many palms as it gives out 

 litres per minute. 



Not a few minds dwelt many years ago upon the possibility of 

 establishing routes across the desert, but that was generally consid- 

 ered chimerical when account was taken of its dangers, known and un- 

 known, the hostility of the races that inhabit it, the length of the 

 marches under a burning sun, over a burning sand, relying upon occa- 

 sional wells for water, and liable to utter destruction if Saught in the 

 path of one of those terrific storms. Still, having a colony on the 

 north coast of the continent and another on the west coast, it is not to 



