162 Observations on the Cause of the Spouting 



between compact and impermeable rocks ; 2dly, Afford this 

 water, by means of a well artificially bored, the possibility of 

 i-ising to a height proportional to that of the level from which it 

 comes ; and, 3dly, Prevent, by tubes inserted into the bored 

 well, the spreading of the ascending water in the surrounding 

 sand, or in the cracks and fissures of the rocks traversed by^the 

 bore. 



From this it will be seen, that spouting springs may be ob- 

 tained by means of boring, in almost every country that pre- 

 sents in its interior subterranean sheets of water, between the al- 

 ternating and continuous beds of permeable and impermeable 

 deposits, extending to the country or mountains which contain 

 the reservoirs of these water-sheets, and whose bases or slopes 

 are covered by these beds. 



But it is essential to repeat here, that we must not expect ta 

 find wells of this description everywhere, as has been thought- 

 lessly asserted ; for, on the one hand, the nature of tlie ground 

 sometimes absolutely prevents it, as in granite districts; and, on 

 the other hand, it is possible that a perforation, made even at a 

 very small distance from a bored well affording water, may not 

 yield any, should the latter, for example, be fed by a subterra- 

 nean current, in place of being supplied by a sheet of water, or 

 should the perforation be made upon the extremity of a basin 

 with inclined strata resting upon a formation of a different na- 

 ture. 



We shall not here enter upon any details respecting the art 

 of boring artesian wells, such not being our object. M. Gar- 

 nier's Manuel du Jbntenier-sondeur contains all that can be de- 

 sired on the subject. 



Taking a general view of what we have said, we deduce the 

 following consequences, which we believe to have been suflHl- 

 ciently demonstrated. 



There exist great subterranean sheets of water at vaiious 

 ' depths. These sheets are more commonly met with in the plane 

 of superposition of strata of different formations. They however 

 frequently occur at various heights in the great masses, such as 

 those of clay, chalk, and even marine limestone containing 

 cerithia, when these masses are entire, and of great thickness. 



