486 Bibliographical Notices. 



BIBLIOGRAPHICAL NOTICES. 



A Geological Inquiry respecting the Water-bearing Strata of the 

 country around London, with reference especially to the Water- 

 Supply of the Metropolis. By J. Prestwich, Juq., F.G.S. 

 London : Van Voorst. 



At tlie present time, wLen the Water question is engaging the atten- 

 tion of the Government and the inhabitants of the metropohs, the 

 appearance of this work is opportune, and more worthy especial no- 

 tice, as the author, in deviating from all the previous recommendations 

 on this subject, has entered upon a new field of inquiry, and suggested 

 the prohabihty of obtaining an ample supply of the important ele- 

 ment from sources not hitherto rendered available for the purpose, as 

 far at least as London is concerned. 



The author is well known for his researches into the geological 

 structure of the coxmtry aromid London, and during his investiga- 

 tions has thus had ample opportunities of making himself acquainted 

 with the chemical and mineral characters, the permeability and ex- 

 tent of the various strata. These observations, as well as others 

 subsequently undertaken and bearing more immediately upon the 

 subject under notice, are concisely embodied in the volume before us, 

 with a ^'iew of supplying some portion of geological information upon 

 the general question of Artesian wells ; not however " with any pur- 

 pose of treating it in that detail which the special nature of the sub- 

 ject would require, but rather with the hope of calhng attention to 

 the practical application of geology in an important oeconomical 

 question, and of establishmg some general principles which may serve 

 to guide to further and more exact investigations." 



M. Boue long ago observed, in his observations on the value and 

 importance of Artesian wells, that correct data upon which the en- 

 gineer should found his operations could only be obtained from the 

 geologist. Mr. Prestwich proposes to adopt the Artesian system — a 

 system having its advocates and opponents, but which we believe has 

 not been fairly discussed, partly from a notion that seemed to prevail 

 of its uncertainty and value, partly in consequence of the operation 

 being generally restricted to the tertiary strata, i. e. the sands above 

 the chalk, and no suggestion having arisen as to its application to 

 lower and more copious water-bearing strata, i. e. the sands below the 

 chalk, but which it is the special object of the present work to sug- 

 gest. Most of our readers are aware that London is situated towards 

 the centre of a large trough-shaped district, formed of a series of 

 strata belonging to the tertiary and cretaceous deposits, cropping out 

 in zones around it. By piercing the superincumbent strata down to 

 the lower cretaceous deposits, comprising the upper and lower green- 

 sand, the presumed new sources of supply will be found. When we 

 examine the effective area of these deposits in comparison with those 

 of other water-bearing strata as indicated in the geological map which 

 accompanies the volume, and consider their permeability and the 

 amount of rain-fall, we shall be prepared for the following remark : — 



" The total superficial area of the Upper Greensand occupies 1 73 



