88 GEOLOGY OF THE ISLE OF WIGHT. 



Drift, or alluvial soil . . . . 38 feet. 



London clay 304 * — 



Plastic sands and clays ... 97 — 



Chalk 821 — 



This well yields by pumping 15,000 cubic feet of 

 water daily, but the quantity is only one half of 

 that required, and it will be necessary to continue 

 the borings till the firestone is reached (probably 

 a further depth of from 1 50 to 200 feet) before an 

 adequate flow of water is likely to be obtained.f 

 The impervious blue chalk-marl or gait, which 

 underlies the firestone, generally supports an abun- 

 dant sheet of water ; but whether a stream will 

 rise to the surface is extremely uncertain, and 

 depends on the level from which the water is 

 derived that feeds this subterranean reservoir, and 

 the condition of the basin which sustains \t.\ 



The branch of the South-western railway that 

 extends to Gosport, cuts through a few ridges of 

 tertiary clays, sands, and gravel, capped with drift, 

 but these present no sections of particular in- 



• Many of the characteristic shells of these strata were brought up by the 

 borer. 



t See an admirable Address on this subject to the Mayor of Southampton 

 and the Members of the Artesian Well Committee, by the Very Rev. Dr. 

 Bnckland; July, 1845. At the late meeting of the British Association of 

 Science at Southampton, the president, Sir Roderick Murchison, and several 

 other eminent geologists, examined the borings, and recommended the con- 

 tinuance of the operations till the firestone was reached. 



; In the chalk districts of t he south-cast of Sussex copious streams of the 

 purest water rise from the junction of the grey mail with the white chalk. 



