AKTESIAN WELLS T75 throwing up a continual jet. The principle is precisely that of our artificial fountains. By raising the water above the surface in a pipe, and letting it flow over, convenient water power is obtained ; artesian wells are applied to this purpose at many localities in France, the water they supply being found sufficient to run heavy machinery. From the great depth at which the currents of water are reached, their supplies may be regarded as permanent. A well at Aire in Artois, France, which was bored over a century ago, has since then flow- ed steadily, the water rising 11 ft. above the surface at the rate of 250 gallons a minute; and at Lillers (Pas-de-Calais) one well has flowed steadily since the year 1126. In the vicinity of London it is observed that the height to which the water rises diminishes as the number of wells is increased. In 1838 the supply of water from them was estimated at 6,000,000 gallons daily, and in 1851 at nearly double the amount, and the average annual fall of the height of the water is about 2 ft. But in cases of single wells, the supply of water or the height to which it rises is seldom known to vary. From their depth, also, the water brought up is warmer than that found near the surface. This increase of temperature with the depth takes place at different rates in different places. At Paris, where the mean temperature at the surface is 51 F., the water of the ar- tesian well of Grenelle is 82 from a depth of 1,797 ft., which is about 1 for every 58 ft. deep. At St. Louis, the temperature of the water at 1,515 ft. is 18-18 F. higher than the mean temperature at the surface, making the increase 1 for every 83-3 ft. descent. At Charleston, S. C., the temperature of the water at the surface is 68 F. ; at 500 ft. it is 73-5; at 1,000 ft., 84 ; and at 1,106 ft., 88. The average rate of increase is about 1 for every 52 ft., as stated by Prof. Hume of the state military academy. The hot springs that flow out to the surface in many parts of the world are natural artesian wells rising from great depths. In Virginia these springs are found along the lines of great faults or breaks in the stratifica- tion of the rocks, by which formations usually separated by thousands of feet are brought into contact with each other. Warm waters obtained by artesian wells have been applied to useful purposes connected with manufactur- ing. They are especially valuable where pure water of a uniformly warm temperature is required. In Wurtemberg large manufactories are warmed by the water being sent through them in metallic pipes ; a constant temperature of 47 is thus maintained when the tempera- ture without is at zero. Hospitals and green- houses are also kept warm in the same manner. The strata of clays, sands, and limestones, which form the tertiary basins of London and Paris, are particularly well arranged for fur- nishing water by artesian wells. Covering areas of many square miles, the slope of the strata is toward the centre of the basin, and here, at the depth to which these reach, the waters must collect in large quantities. The strata, moreover, are not difficult to penetrate by boring. In these basins are concentrated the greatest number and the most expensive of these wells. The famous Grenelle well in the Paris basin was commenced in 1833, with the expectation of obtaining water at 1,200 or 1,500 ft., in the secondary greensand forma- tion, which underlies the chalk, the uppermost member of this series. For the first 50 ft. the bore was 12 in., which was then reduced to 9 in. for the next 1,050 ft. ; a second reduction to 7i in. was made till the depth of 1,300 ft. was reached, where there was a final decrease to 6 in. At 1,500 ft. the government would have abandoned the enterprise but for the urgent appeals of M. Arago. It was .continued till, on Feb. 26, 1841, at the depth of 1,797 ft., the boring rod suddenly penetrated the arch of rock over the subterranean waters, and fell 14 ft. In a few hours the water rose to the sur- face in an immense volume and with great violence, bringing up sand and mud. To check the supply a vertical pipe was raised many feet into the air, in which the water rises and flows over. The water is perfectly limpid, and flows at the rate of 500,000 gallons in 24 hours. It is used for warming the hospitals at Grenelle, as its temperature is uniformly 82 F. A well very similar to that at Grenelle, though of in- creased diameter, was begun at Passy, two miles distant, in September, 1854, and finished Sept. 24, 1861. The boring began at a height above the sea of 305*2 ft., and that at Grenelle at 121-3 ft. ; the depth is 1,923 ft., and diame- ter within the tube 2-4 ft. The flow from this well began slowly, but on Sept. 27 had reached over 5,500,000 gallons per day. The yield at the mouth was greatly decreased when raised through a tube 25 ft. high ; a like result fol- lowed at Grenelle, where the yield was 440 gallons per minute at the surface, but de- creased to 135 gallons when forced through a tube 33 ft. high. That these two wells, though two miles apart, drew their supply from the same source, is evident both from their tem- perature, 82 F. in each, and from the fact that the opening of the Passy well reduced the flow at Grenelle from 135 to 100 gallons per minute, though it is anticipated that by forcing the water at Passy through a still higher tube the yield at Grenelle may be increased. This de- pendence of several wells upon one source is shown also in the Pennsylvania oil region, where the water from one well, when not pumped out, often finds an exit through the tubes of those adjoining. The work on both the above-mentioned wells was much delayed by accidents. When that at Grenelle was at a depth of 1,254 ft., the drill broke off and fell with 270 ft. of rods to the bottom ; 15 months were spent in breaking these and removing the pieces. The tubing in the Passy well was also burst by the external pressure of sand and water, and had to be removed and new tubes
