A French engineer, M. Mullot, invented a simple method of bringing to the surface water from any one of several successive accumulations at different depths, or of raising it, unmixed, from two or more of them at once. It consists in employing concentric tubes, one within the other, leaving a space for the rise of water between them, and reaching each to the sheet from which it is intended to draw.
[401] Many more or less probable conjectures have been made on this subject, but thus far I am not aware that any of the apprehended results have been actually shown to have happened. In an article in the Annales des Ponts et Chaussées for July and August, 1839, p. 131, it was suggested that the sinking of the piers of a bridge at Tours in France was occasioned by the abstraction of water from the earth by artesian wells, and the consequent withdrawal of the mechanical support it had previously given to the strata containing it. A reply to this article will be found in Violett, Théorie des Puits Artésiens, p. 217.
In some instances the water has rushed up with a force which seemed to threaten the inundation of the neighborhood, and even the washing away of much soil; but in those cases the partial exhaustion of the supply, or the relief of hydrostatic or elastic pressure, has generally produced a diminution of the flow in a short time, and I do not know that any serious evil has ever been occasioned in this way.
[402] See a very interesting account of these wells, and of the workmen who clean them out when obstructed by sand brought up with the water, in Laurent's memoir on the artesian wells recently bored by the French Government in the Algerian desert, Mémoire sur le Sahara Oriental, etc., pp. 19, et seqq. Some of the men remained under water from two minutes to two minutes and forty seconds. Several officers are quoted as having observed immersions of three minutes' duration, and M. Berbrugger alleges that he witnessed one of five minutes and fifty-five seconds. The shortest of these periods is longer than the best pearl diver can remain below the surface of salt water. The wells of the Sahara are from twenty to eighty mètres deep.
It has often been asserted that the ancient Egyptians were acquainted with the art of boring artesian wells. Parthey, describing the Little Oasis, mentions ruins of a Roman aqueduct, and observes: "It appears from the recent researches of Aim, a French engineer, that these aqueducts are connected with old artesian wells, the restoration of which would render it practicable to extend cultivation much beyond its present limits. This agrees with ancient testimony. It is asserted that the inhabitants of the oases sunk wells to the depth of 200, 300, and even 500 ells, from which affluent streams of water poured out. See Olympiodorus in Photii Bibl., cod. 80, p. 61, l. 17, ed. Bekk."—Parthey, Wanderungen, ii, p. 528.
In a paper entitled, Note relative à l'execution d'un Puits Artésien en Egypte sous la XVIII dynastie, presented to the Académie des Inscriptions et Belles Lettres, on the 12th of November, 1852, M. Lenormant endeavors to show that a hieroglyphic inscription found at Contrapscelcis proves the execution of a work of this sort in the Nubian desert, at the period indicated in the title to his paper. The interpretation of the inscription is a question for Egyptologists; but if wells were actually bored through the rock by the Egyptians after the Chinese or the European fashion, it is singular that among the numerous and minute representations of their industrial operations, painted or carved on the walls of their tombs, no trace of the processes employed for so remarkable and important a purpose should have been discovered. See Appendix, [No. 56].
It is certain that artesian wells have been common in China from a very remote antiquity, and the simple method used by the Chinese—where the borer is raised and let fall by a rope, instead of a rigid rod—has been lately been employed in Europe with advantage. Some of the Chinese wells are said to be 3,000 feet deep; that of Neusalzwerk in Silesia—the deepest in Europe—is 2,300. A well was bored at St. Louis, in Missouri, a few years ago, to supply a sugar refinery, to the depth of 2,199 feet. This was executed by a private firm in three years, at the expense of only $10,000. Another has since been bored at the State capitol at Columbus, Ohio, 2,500 feet deep, but without obtaining the desired supply of water.
[403] "In the anticipation of our success at Oum-Thiour, every thing had been prepared to take advantage of this new source of wealth without a moment's delay. A division of the tribe of the Selmia, and their sheikh, Aïssa ben Shâ, laid the foundation of a village as soon as the water flowed, and planted twelve hundred date palms, renouncing their wandering life to attach themselves to the soil. In this arid spot, life had taken the place of solitude, and presented itself, with its smiling images, to the astonished traveller. Young girls were drawing water at the fountain; the flocks, the great dromedaries with their slow pace, the horses led by the halter, were moving to the watering trough; the hounds and the falcons enlivened the group of party-colored tents, and living voices and animated movement had succeeded to silence and desolation."—Laurent, Mémoires sur le Sahara, p. 85.
[404] The variety of hues and tones in the local color of the desert is, I think, one of the phenomena which most surprise and interest a stranger to those regions. In England and the United States, rock is so generally covered with moss or earth, and earth with vegetation, that untravelled Englishmen and Americans are not very familiar with naked rock as a conspicuous element of landscape. Hence, in their conception of a bare cliff or precipice, they hardly ascribe definite color to it, but depict it to their imagination as wearing a neutral tint not assimilable to any of the hues with which nature tinges her atmospheric or paints her organic creations. There are certainly extensive desert ranges, chiefly limestone formations, where the surface is either white, or has weathered down to a dull uniformity of tone which can hardly be called color at all; and there are sand plains and drifting hills of wearisome monotony of tint. But the chemistry of the air, though it may tame the glitter of the limestone to a dusky gray, brings out the green and brown and purple of the igneous rocks, and the white and red and blue and violet and yellow of the sandstone. Many a cliff in Arabia Petræa is as manifold in color as the rainbow, and the veins are so variable in thickness and inclination, so contorted and involved in arrangement, as to bewilder the eye of the spectator like a disk of party-colored glass in rapid revolution.
In the narrower wadies, the mirage is not common; but on broad expanses, as at many points between Cairo and Suez, and in Wadi el Araba, it mocks you with lakes and land-locked bays, studded with islands and fringed with trees, all painted with an illusory truth of representation absolutely indistinguishable from the reality. The checkered earth, too, is canopied with a heaven as variegated as itself. You see, high up in the sky, rosy clouds at noonday, colored probably by reflection from the ruddy mountains, while near the horizon float cumuli of a transparent ethereal blue, seemingly balled up out of the clear cerulean substance of the firmament, and detached from the heavenly vault, not by color or consistence, but solely by the light and shade of their prominences.