as these, in all probability came from the Nile, and as the sand excavated from those wells is much the same as that of the Algerian borings, 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 volume than at first. He studied the matter, as did also M, Ludovic Ville, Directeur des Mines d'Algérie. The causes of the lessening of the flow were found to be the crushing-in of the tubes, the accumulation 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 running streams of winter and make a reservoir for the summer, it should be done, and artesian borings made where such streams are not available. Among other places, M. Grad maintained that the fertile basin of the Hodna, situated on the Algerian plateau, 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 hostility 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 distributed 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 considered chimerical when account was taken of its dangers, known and unknown, the hostility of the races that inhabit it, the length of the marches under a burning sun, over a burning sand, relying upon occasional wells for water, and liable to utter destruction if caught 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
