4 VREDENBURG : RECENT ARTESIAN EXPERIMENTS IN INDIA. 



the one at which it was tapped, as soon as the impermeable layer 

 is pierced; and if there be a sufficient difference in the altitudes of 

 the surface at the well and at the source of supply, or fountain-head, 

 the water may rise higher than the level of permanent saturation 

 of the neighbourhood of the well, and may even overflow at the 

 surface. Only to such flowing wells is the name " artesian " applied 



Uncertainty of nomen- by certain authors, while according to others, 

 clature. ^e name should be given to all wells in which 



water rises to a higher level than that at which it was tapped. It is 

 this latter view which was eventually taken by Mr. Medlicott : 

 " Partial artesian action is always possible when percolation along 

 the planes of bedding is much more easy than across them, and this 

 seems to be a general character of stratification independently of 

 any visible impervious beds." 1 The exclusion of all but flowing 

 wells from the class of artesian wells is a somewhat artificial restric- 

 tion. Two neighbouring wells may tap the same underground 

 reservoir, and owing to a difference of a few feet in the altitude of 

 the places at which they have been sunk, one of them may over- 

 flow and not the other, although all the other conditions are just 

 the same. Moreover, a non-flowing well may, by means of pumping, 

 prove of just as much practical utility as a flowing one, if the supply 



is abundant. A flowii.g well, on the other hand, may be of very 

 little use if it gives a small delivery for a given diameter of the 

 bore : the Lucknow boring struck at a depth of 1,189 * eet a sheet of 

 water under sufficient pressure to overflow at the surface ; but the 

 delivery was insignificant. 



The conditions of artesian reservoirs are very completely dis- 



Perfect and imperfect cussed in a treatise by Prof. Chamberlin pub- 



reservoirs. lished by the Geologica j Survey of the United 



States. 3 Artesian reservoirs were divided by him into "perfect 



1 Rec. Geol. Surv. Ind., Vol. XVI, p. 20S. 



2 " The requisite and qualifying conditions of Artesian Wells," by T. C. Chamberlin, 

 Fifth Annual Report of the United States Geological Survey, pp. 125-173. 



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