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from the Himalayas, rises 32 feet from April to August, and creates a flood of 100 miles in width. The Euphrates, from Mount Ararat, rises 12 feet between March and June, and covers the Babylonian plains. The Mississippi, flowing from the Stony Mountains, rises with the melting of the snows from March till June, forming a vast belt of watered surface. At the distance of 1000 miles from the ocean it is said to rise 50 feet, while nearer the sea its rise is considerably reduced by the vast tract which it covers.

22. The periodical rise of river waters gives facilities for their systematic distribution over the higher districts to a most important extent by the construction of canals, of which the ancient Egyptians largely availed themselves. Their canals, branching in various directions, are said to have amounted to 80 in number, and to have extended to 60 or 100 miles each in length. Similarly, the great cavities, called the Lakes of Moris, Behira, and Mareotis, are considered to have been reservoirs artificially formed for collecting vast stores of water to be afterwards distributed for irrigation.

23. Among the means of artificial supply, the construction of wells has always been resorted to as a certain method of obtaining water in cases where no other was practicable. Failing rain and rivers, subterranean sources have, from the earliest times, been sought for, the formation of wells being one of the most ancient engineering expedients. The primitive wells of Greece are described as being surmounted with massive marble cylinders; those of Thrace consisted of arched excavations in the sides of rocks, where the water was directly obtainable from springs; the springs of Turkey were converted into fountains, and "the castle of Cairo contains a curious well, sunk in the rock to the depth of 280 feet, and having

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a circumference of 42 feet. The water of this well filters through the sand from the Nile, and, being impregnated in its passage by salt and nitre, it has a brackish taste.”

24. As a modern discovery, or, properly, revival, that of Artesian Wells is a valuable source of the artificial supply of water. The theory of these wells is simply this-that water, descending through the permeable strata of the earth, and reaching either a cavity or a bed of spongy materials, will accumulate there if its egress is prevented by an impervious surrounding stratum, and, if an artificial opening or well be made into this waterbearing bed, the water will rise upward in it to a height, and with a force, due to the superior elevation and fertility of the source. Having been long adopted in Artois, these wells have received the modern name of Artesian wells. This contrivance appears to have been introduced into this country from France and Italy about the year 1790. At Mortlake, near the Thames, a well was driven, through the clay and sand into a bed of soft chalk to a depth of 375 feet, and a good supply obtained through a bore of 31⁄2 ins. in diameter. The strata penetrated were as follow:-gravel, 20 ft.; London clay, 250 ft.; plastic sands and clays, 55 ft.; hard chalk with flints, 35 ft.; soft chalk, 15 ft.

25. The celebrated Artesian Well at Grenelle, in France, formed under the direction of M. Mulot, is an instance of the difficulties and success of these works. This work occupied eight years and a half of anxious exertion, and the water first rose on the 26th of February, 1841. The strata bored through are as follows, measured from the surface:-the second column shows the depth of each stratum, and the third column exhibits the resemblance between the formations of the basins of London and Paris.

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Corresponding with the London formations, viz. :

Formations of
London and

Paris Basins.

Plastic clay.

White chalk.

Gray chalk.

Chalk marl.

The sand, in which the water is obtained, continues below this depth. The boring was commenced at a diameter of 20 inches, and diminished as the tubes descended, so that at the depth of 576 feet, employing 4 columns of tubing, the diameter was 12 inches. The fifth column

of tubing reaches 1148 feet, with a diameter of 10 inches. The sixth reaches 1345 feet, and has a diameter of 81 inches. The seventh, and last tube, reaches 1771 feet, with a diameter of 6 inches. The lower 23 feet in the clay are not tubed. During the progress of the work several accidents of a discouraging nature occurred : the rods and chisels sometimes became detached, and fell to the bottom. The chisel also, when in the chalk, sank at one stroke 85 feet, and became so firmly fixed, that M. Mulot found it necessary to enlarge the hole on all sides. All difficulties were at length, however, surmounted, and on the day mentioned the rods suddenly sunk several feet; the workmen found that all resistance had ceased, and that the water-bearing stratum was attained. After a few hours a column of water rose to a height of nearly 2000 feet. The subsequent operation of lining the bore was a work of great importance, in order to prevent the sides of the hole falling in through any of the less compact strata, and at the same time prevent the possibility of the water escaping, or the pressure being lost by any fissures that exist, or may be formed in the strata through which the water passes. The arrangement of these tubes requiring a regular diminution of diameter in the manner of the tubes of a telescope, it is essential that the relative dimensions be calculated with great exactness, otherwise the lower tubes are found to become too small to admit the water, and it is then necessary to remove the whole of the tubes deposited, and enlarge the bore accordingly. At Grenelle it was five times necessary to remove the whole of the placed lining, and enlarge the bore of the well. Wrought iron had been employed for lining on previous occasions, but had failed, one remarkable instance of which may be mentioned. The water of an

Artesian Well at St. Cyr, near Tours, rises from the sand beneath the chalk, and the tubular lining to the well was of iron. The supply, however, diminished in every succeeding year, and M. Bretonneau caused the tubing to be drawn up, which was ths of an inch in

thickness, and found well preserved; but at the joints of the pipes several circular holes were discovered, two or three centimes in diameter. This effect has been accounted for by an assumed electro-chemical action, but, however caused, it leads to the rejection of iron as a material for the tubing. Copper tubes th of an inch in thickness have been applied at Grenelle.

26. The supply from the Puits de Grenelle was reported in 1841 to exceed 880,000 gallons every 24 hours, and the cost of the work was about £10,000. Some of the Artesian Wells sunk at Tours were found to yield less than when opened. A greater number, however, have produced an augmented quantity, and the probability is that the deficiencies have arisen from imperfections in the lining of the bores. In the pro

vince of Artois, where Artesian Wells have existed upwards of 300 years, no diminution has ever been observed. The subterranean sheet of water which supplies these extends over a space of several hundred square leagues, in comparison with which the outlets to these wells are almost inappreciable.

27. The deficiency of supply by which Artesian Wells are rendered inoperative usually becomes evident before any very great depth is reached, although, if the waterbearing stratum happens to crop out at any points however distant from the boring, the supply is liable to deficiency, and the pressure necessary to force the water upwards is also perhaps lost. Thus, previous to the operations at Grenelle, just described, a boring was executed at the Jardin des Plantes; but the water never

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