Revieus — C. E. Be Ranee' & Water Supply. 89 



Eance has collected the facts and opinions of various authors who 

 have investigated the subject, as to the capability of these wells 

 yielding a good and permanent supply, especially in connexion with 

 the Metropolis (pp. 183, 187, 241). 



That they may be an effective source, under certain conditions, 

 there can be little doubt ; but the calculation must be based not 

 upon the amount of rainfall over the exposed surface area of the 

 permeable rock, but on the probable quantity which finds its way 

 to the underground reservoir to supplj"- the Artesian well (see 

 pp. 183-4). 



It is well known that the level of the water in the London arte- 

 sian wells, derived from the Lower Tertiary sands and Upper Chalk, 

 has steadily decreased with the increase of their number ; still it was 

 expected by sinking to lower permeable strata, that a better supply 

 might be obtained, and thus obviate the use of the Thames and Lea 

 streams. The Elvers Pollution Commission (Sixth Report) believe 

 that within a forty mile radius of London a sufScient volume of 

 deep-well and spring water can be obtained for the wants of the 

 metropolis, from the Chalk and Upper Greensand ; but as Dr. John 

 Evans, F.R.S., remarks, — while they admit that any water drawn 

 from the subterranean reservoir in the Chalk by artificial means will 

 be at the expense of the streams which now flow through the vallej's 

 in the Chalk area, they do not give even a passing consideration 

 to the effect upon that area of abstracting from it its natural supply 

 of water, how it will affect the existing wells, the mill-streams, and 

 the fertility of the district dependent on the supply of moisture 

 (Ann. Address, Geol. Soc, 1876, p. 70). 



The Eoyal Commission on Water Supply laid great stress on the 

 underground store of water supposed to be contained in the Lower 

 Gi'eensand (Report, 1869, p. 87), and which had been previously 

 advocated by Prof. Prestwich in his "Water-bearing Strata," 1851. 



The experience since gained by the borings at present made is not 

 favourable to the scheme (p. 243), as far as the immediate neighbour- 

 hood of London is concerned. 



In other districts, however, the Lower Greensand has yielded 

 effective supplies ; thus, at Cambridge, although Mr. Ue Ranee men- 

 tions but one artesian well at Harston 200 feet deep (p. 154), 

 Prof. Prestwich states that artesian wells are numerous, and that 

 much of the water is evidently pure and good (Water-bearing Strata, 

 1851, pp. 90, 167, 183, 193). Also Prof. Bonney, Camb. Geol. p. 80. 



There are many artesian wells at Harston and all round this Gault 

 district which draw their water from the Lower Greensand, some of 

 which overflow. A well has been bored through the Gault at Cherry 

 Hinton for the Cambridge water works. M.G.S. Camb. Dist. p. 129. 



Again, in Bedfordshire, Prof. Chapman remarks (Phil. Mag. 1852, 

 2nd ser. vol. iv. p. 102) : " There are perhaps few localities in which 

 the subject of Artesian wells can be better studied than in the valley 

 between Silsoe and Barton-in-the-Clay ; the latter village lying 

 under the bold escarpment of the Chalk with its projecting spurs 

 and rounded hollow coombes, and the former on the opposing range 



