Bibliographical Notices. 487 



square miles, and that of the Lower Greensand 650. The average fall 

 of rain on them amounts respectively to about 191,000,000 and 

 695,000,000 of gallons daily. As also the thickness of the one for- 

 mation averages 50 feet, and that of the other 367 feet, the latter con- 

 sisting in great part of the most perfectly permeable strata, I cannot 

 but think that, taking the question in all its bearings, — considering the 

 results obtained from strata of much more limited dimensions, and the 

 relative fall of rain in the several districts, — we have in these facts a 

 further argument in favour of the conclusions to which we have be- 

 fore arrived, viz. that a daily supply of from six to ten million gal- 

 lons of water might be drawn from the Upper Greensand, and of from 

 thirty to forty million gallons from the Lower Greensand, beneath 

 London and within a circle of five miles around it. For these large 

 supplies the open texture of the sands themselves affords naturally 

 the necessary channels and reservoirs. All parts of the surface can 

 communicate freely with the subterranean reservoir, which presents a 

 capacity for storage comparatively unlimited in its extent. If it were 

 not to rain for a whole year, the effect upon the volume of water held 

 in the strata would be scarcely perceptible ; for let it be borne in 

 mind that the effective permeable beds of the lower greensand are 

 200 feet thick, that they occupy an area above and below ground of 

 4600 square miles, that amass of only 1 mile square and 1 foot thick 

 will hold more than 60,000,000 gallons of water, and some idea 

 may be then formed of the magnitude of such an underground reser- 

 voir. A fall of 1 foot in the water-level throughout the whole area 

 of outcrop would give more than the quantity of water required for a 

 year's consumption of London." 



It will be unnecessary here to extract further details, but merely to 

 direct the reader to some of the principal contents of the work, which 

 includes a general account of the geological structure of the country 

 around London, with reference to the conditions which determme the 

 water-bearing capacity of the several deposits, their extent and struc- 

 ture, thickness and probable depth beneath London, and to the rain- 

 fall upon them, followed by a comparison of the dimensions and re- 

 lations of these strata, as to the quantity of water that may be pro- 

 bably obtained from the different groups, and the effects of disturb- 

 ances of the strata on the subterranean passage of the water. A 

 variety of interesting facts are also given in the appendix, including 

 the analyses of the waters of some Artesian wells in France, and the 

 river and well waters used in and near the metropolis. 



The numerous references throughout to foreign and English autho- 

 rities bearing on the subject, fully indicate that the author has spared no 

 labour to render this work as practically usefid as possible to the geo- 

 logist, the engineer, and those interested in the water-supply ; and the 

 reader who peruses the amount of facts and carefully-considered e\'i- 

 dence collated in its pages will feel that there are reasonable grounds for 

 believing " that there probably is no large city in Europe, the situation 

 of which is so peculiarly favourable as that of London, for obtaining by 

 means of Artesian wells an abundant supply ,q^ water which would 

 prove both pure and good." . 



