. ORIGIN AND NATURE OF SPRINGS. 5 



so that a water supply is not afforded, it may be 

 possible to reach the reservoirs in the deep strata 

 below by borings, and these extensive perforations 

 are called artesian wells. They are not always 

 successful, as it is impossible, from geological obser- 

 vations, to determine whether the different strata 

 are favorable or unfavorable. It may be that there 

 exists a porous stratum at a distant point of suffi- 

 cient area to collect the rain-fall, and that there are 

 seams between the impermeable rocks, so that it 

 can pass along down to a lower level ; but it is not 

 certain that it is held in the deep basins where we 

 might expect to find it. Dislocations in the strata 

 are common, and through them the water may leak 

 out and seek a lower stratum, or a natural vent, by 

 which it can rise to the surface at a point lower 

 than the well. Any one who engages in deep bor- 

 ings for water does so at considerable risk, as no 

 geologist or chemist can give him positive assur- 

 ances of success. In this country we have numerous 

 artesian wells, some of them of great depth. The 

 famous St. Louis well is about 1,900 feet deep, and 

 the force with which the water rises is very great. 

 It is however entirely unsuited to domestic uses, 

 being charged with mineral constituents derived 

 from rocks and minerals over and through which it 

 passes in its course. Offensive gases are often 

 mingled with water coming from deep wells, and 



