46 THE APPLICATIONS OF PHYSICAL FORCES. [BOOK i. 



is seen in the geological section of the strata which constitute the Paris 

 basin, stretching from Paris to the upper level of the basin, at the 

 plain of Langres. The beds of water-bearing sand which are met with 

 at depths of 548 and 570 metres, in the case of the borings of the 



FIG 26. -Artesian well at Passy 



artesian wells of Grenelle and Passy, are covered by a series of rocks, 

 principally a bed of chalk of considerable thickness. All these 

 layers, gradually rising to the surface, come out at points by so much 



