420 ARTESIAN WELLS. 



Artesian Wells are most available, and of the greatest 

 use, in low and level districts where water cannot be obtain- 

 ed from superficial springs, or by ordinary wells of mode- 

 rate depth. Fountains of this kind are known by the name 

 of BIoiv ivells, on the Eastern coast of Lincolnshire, in the low 

 district covered by clay between the Wolds of Chalk near 

 Louth, and the Sea-shore. These districts were without any 

 springs, until it was discovered that by boring through this 

 clay to the subjacent Chalk, a fountain might be obtained, 

 which would flow incessantly to the height of several feet 

 above the surface. 



In the King's well at Sheerness sunk in 1781 through the 

 London clay, into sandy strata of the Plastic clay formation, 

 to the depth of 330 feet, the water rushed up violently from 

 the bottom, and rose within eight feet of the surface. {See 

 Phil. Trans. 1784.) In the years 1828 and 1829 two more 

 perfect Artesian wells were sunk nearly to the same depth 

 in the Dock yards at Portsmouth and Gosport. 



Wells of this kind have now become frequent in the neigh- 

 bourhood of London, where perpetual Fountains are in some 

 places obtained by deep perforations through the London 



both strata is thus brought to the surface by one Bore Hole of sufficient 

 size to contain a double pipe, viz. a smaller pipe included within a larger 

 one, with an interval between them for the passage of water ; thus, the 

 smaller pipe b brings up the water of the lower stratum B, to the highest 

 level of the fountain b", whilst the larger pipe a, brings up the water from 

 stratum A to the lower level a': both these streams are employed to supply 

 the Canal-basin at St. Ouen, above the level of the Seine. Should the lower 

 stratum B contain pure water, and that in the upper stratum A be tainted, 

 tiie pure water might by this apparatus be brought to the surface through 

 the impure, without contact or contamination. 



In common cases of Artesian wells, where a single pipe alone is used, if 

 the Boring penetrates a bed containing impure water; it is continued deeper 

 until it arrives at another stratum containing pure water ; the bottom of the 

 pipe being plunged into this pure water, it ascends within it and is conduct- 

 ed to the surface through whatever impurities may exist in the superior 

 strata. The impure water, through which the boring may pass in its 

 descent, being e.^cluded by the pipe from mixing with the pure water 

 ascending from below. 



