BY A. GIBB MAITL.A.ND, C.E., F.G.S. 41 



" of Upper Chalk, and at Dover Castle prove that the 

 " pressure of ocean water is not sufficient to penetrate the 

 '' strata, which is still further supported by the dryness of 

 " collieries and copper mines worked under the sea, and the 

 " plentiful supply of fresh water obtained in the artesian wells 

 " sunk in the sea at Spithead Forts. If the plane of saturation 

 " by artificial means were lowered the fissures or outlets which 

 " allow the escape of fresh water at or beneath the sea level 

 " would no longer have sufficient head or pressure to force 

 " back the sea water, and the sea would flow in. This has 

 " actually occurred at Calais wherein an unsuccessful boring 

 " for water a brackish stream was met in the Upper Chalk 

 " at 160 metres, or 70 feet, and Paheozoic rocks at 836 

 " metres." * 



Where accurate observations extending over considerable 

 periods have been made on the wells in North America, it has 

 been found that the pressure recorded increases and diminishes 

 with a regularity which points to dependence upon the seasonal 

 variations on the higher ground of the catchment area, and also 

 to ihe permanence of the supply, for so long as the rain falls 

 and the snow melts in that area so long will the supply 

 continue. 



* The Water Supply of Enf,'land and Wales ; C. E. De Ranee. London : 1882. 



