1 



392 



AETESIAN WELLS. 



stratum 



[Ch. XVII. 



The water will then rush out, just as the 

 liquid from a large barrel which is tapped, and it will rise t 

 a height corresponding to the level of its point of departure 

 or, rather, to a height which balances the pressure previously 

 exerted by the confined waters against the roof and sides of 

 the stratum or reservoir a a. In like manner, if there happen 

 to be a natural fissure c, a spring will be produced at the 

 surface on precisely the same principle. 



Among the causes of the failure of Artesian wells, we may 

 mention those numerous rents and faults which abound in 

 some rocks, and the deep ravines and valleys by which many 

 countries are traversed; for, when these natural lines of 



remains 



to escape by artificial issues. We 



or 



by the 



impervio 



may 



from adjoining high lands to some trough in an opposite di- 

 rection, as when the borings are made at the foot of an 

 escarpment where the strata incline inwards, or in a direction 

 opposite to the face of the cliffs. 



The mere distance of hills or mountains need not dis- 

 courage us from making trials : for the waters which fall on 

 these higher lands readily penetrate to great depths through 

 highly inclined or vertical strata, or through the fissures of 

 shattered rocks, and after flowing for a great distance, must 

 often re -ascend and be brought up again by other fissures, so 

 as to approach the surface in the lower country. Here they 

 may be concealed beneath a covering of undisturbed hori- 

 zontal beds, which it may be necessary to pierce in order to 



reach them. 



remembered 



waters flowing under ground bears but a remote resemblance 

 to that of rivers on the surface, there being", in the one case, 

 a constant descent from a higher to a lower level from the 



to thfi Sfifl. ! wlifrAns in flip nth fVT. the 



earn 



water may at one time sink far below the level of the ocean, 

 and afterwards rise again high above it. 



Among other curious facts ascertained by aid of the borer, 

 it is proved that in strata of different ages and compositions, 

 there are often open passages by which the subterranean 



I 





















C* 



P 



tbes € 

 borei 



ce 

 jo- 



lid 

 ent 



has 

 Toui 



whei 



feet, 

 matt 

 niue. 



as 



hie 



v 



ma 

 rem: 

 Am( 



norh 



and 



this 

 soni 



milt 



A 



Boc 



broi 

 thrt 



beii 



up 



feet 

 sou 



Wei 



I 



t 



