208 ARTESIAN WELLS IN DORSET AND ELSEWHERE. 



with very limited exceptions, as a sponge, owing to the facility 

 with which the water-level moves up and down, according to the 

 amount of rainfall in those areas, such as the Hampshire and 

 Wiltshire plateau, where the Chalk itself forms the surface. 

 That the surface contours, and consequently the surface-flow, 

 has some influence on the underground flow may be conceded, 

 yet the controlling factors of the latter are in the main "the 

 " difference of pressure along the lines of flow, the varying 

 "texture of the strata traversed, and the disposition of con- 

 tiguous impermeable strata."* In regard also to the degree 

 of artesian pressure existing at any given spot, this may 

 sometimes be modified by the action of springs, which, like 

 excessive pumping, tend to bleed the underground arteries, and 

 thus lower the general water-level for considerable distances. 



* Baldwin-Wiseman, on the "Motion of Sub-surface Water," Q.J.G.S., 

 Vol. 63, p. 93. A sketch map of sub-surface water-levels in the Chalk of Dorset, 

 Wiltshire, and Hampshire is appended to this paper. 



