ARTESIAN WELLS. 419 



by the Fault. (See PI. 67. Fig. 2, d, and PI. 69. Fig. 2. H. 

 L.) 



Besides the advantages that arise to the whole of the Ani- 

 mal Creation, from these dispositions in the structm'e of the 

 Earth, whereby natural supplies of water are multiplied 

 almost to infinity over its surface, a farther result, of vast 

 and peculiar importance to Man, consists in the facilities 

 which are afforded him of procuring arii^cm/ wells, through- 

 out those parts of the world which are best adapted for 

 human habitation. 



The Causes of the rise of water in ordinary artificial wells, 

 are the same that regulate its discharge from the natural 

 apertures which give origin to springs ; and as both these 

 effects will be most intelligibly exemplified, by a considera- 

 tion of the causes of the remarkable ascent of water to the 

 surface, and often above the surface, in those peculiar per- 

 forations which are called Artesian Wells, our attention may 

 here be profitably directed to their history. 



Artesian Wells. 



The name of Artesian Wells is applied to perpetually 

 flowing artificial fountains, obtained by boring a small hole, 

 through strata that are destitute of water, into lower strata 

 loaded with subterraneous sheets of this important fluid, 

 which ascends by hydrostatic pressure, through pipes let 

 down to conduct it to the surface. The name is derived 

 from Artois (the ancient Artesium,) where the practice of 

 making such wells has for a long time extensively pre- 

 vailed.* 



* The manner of action of an Artesian Well is explained by tlie Sec- 

 lion PI. 69. Fig-. 3, copied from Mr. Hericart de Thury's representation of 

 a double Fountain at St. Ouen, wliicli brings up water, from two water- 

 bearing strata at different levels below the surface. In this double foun- 

 tain, the ascending forces of the water in the two strata A and B are dif- 

 ferent : the water from the lowest stratum B rising to the highest level 

 I"; that from the upper stratum A rising only to a'. The water from 



