“The preliminary theoretical determination of the existence of these Artesian conditions is in itself a difficult matter, and can be arrived at only by a thorough acquaintance with the geological disposition of the district.”--(Ninth edition Encyclopedia Britannica.) “The question of a supply of water from deep wells, made by boring, and commonly called artesian, has been somewhat discussed in Philadelphia, but there is no probability that an adequate supply, for the general use of the city could be obtained in that manner; and the quality of the water obtained from such wells varies very much in different localities, depending upon the nature of the strata from which the water is procured, and this Commission can not recommend any dependence upon such plans for the general city supply, attended, as they are, with great expense and extreme uncertainty, and being, in every case, more or less experimental.”--(Philadelphia Water Supply Commission of Engineers, 1875.) The flowing water of the Kissingen spring, Bavaria, is produced by carbonic acid gas. TEMPERATURE OF WELLS. Invariably the temperature of water from great depths is higher than at the surface, this being due to some unknown source of heat in the interior of the globe. In Scotland, the rate of increase of temperature, after permanent degree has been attained, is about one degree Fahrenheit for every forty-eight feet of descent. At Grenelle, the temperature was found to be 1.8 degrees for every 106 feet of descent below the point of constant temperature. The average rate of increase of temperature is one degree for a descent of from forty to fifty feet. The temperature of the boring at Columbus increased, below the permanent line, one degree in every seventy-one feet. EXAMPLES OF ARTESIAN WELLS. The famous well at Grenelle, France, was commenced, by the government, in 1834, and after repeated failures and discouragements almost to abandonment, notwithstanding the urgent representations of the scientist Arago, that water would be found, the end was accomplished at the depth of 1,798 feet, in the year 1843. The diameter of the bore is 3½ inches; capacity, 600 gallons per minute; temperature of water, 82 degrees; height of flow, 128 feet. The expense attending this boring was 300,000 francs. The Passy well, near Paris, supplied from the same water-bearing stratum of the Grenelle, is 1,923 feet deep; 2′ 4″ inches bore at bottom; capacity, 5,582,000 gallons per day; height of flow, 54 feet. The La Chapelle well was started in 1866, with a gigantic bore of five feet seven inches, and by November, 1869, had reached a depth of 1,811 feet, the intention of the engineer being to extend it to a depth of 2,950 feet. At the part of Paris named Butte-aux-Caelles, a well was started, in 1866, of six and a half feet diameter, to be carried down to a depth of 2,600 to 2,900 feet.