The New Student's Reference Work/Artesian Wells
Artesian (är-tē'zhan) Wells are borings straight down into the ground through which water rises above the surface of the ground. The possibility of getting water in this way depends upon the rock formation at a place. There is more or less water in all rocks. Rocks which are sandy and easily broken up part with a greater or less portion of the water they receive. For example, a cubic yard of pure sea-sand can hold about one third its bulk of water. It would part with nearly the whole of this into a well sunk in it and regularly pumped from. Chalk, which is composed of fine particles closely pressed together, holds as large a proportion of water; but from the power of what is called capillary attraction—the same power that lifts the sap in trees—little water would drain into a well sunk in such a rock. Where porous layers of rock are found resting on a layer which is impervious to water and covered by another layer also impervious, the water in the middle layer is held imprisoned. Where these three layers run i across a valley and up a hill on each side, they will be exposed to the air at the top. The falling rain is carried down the middle layer, and gathers at the bottom of the valley, and in time the whole porous layer becomes water logged, and the water at the center is under strong pressure. Now, if a bore is made at the bottom of the valley into the water logged layer, the pressure will force the water above the surface. The most famous artesian well is that at Grenelle near Paris, which was bored in 1833—1841. and whose water is brought from a depth of 1,798 feet. It yields 516½ gallons of water a minute, which is forced thirty-two feet above the surface. The Chinese and Egyptians knew about artesian wells, and they have been bored in the Sahara desert. There are many artesian wells in the United States, where they are utilized for supplying cities, towns, villages and farms with water.