Rev. A In'ing — Water Supply from the Bagshot Beds, etc. 19 



cited above. Comparing these two typical instances with others of 

 similar nature in the district, we may say generally'' that it is only 

 lohere the old for est -lands of the district have been for some time hrolcen 

 up and cidtivated, or lohere, beginning on high ground, a considerable 

 depth of the Upper Sands (perhaps 30 feet at least) is pierced, that 

 water free from considei'able pollution by vegetable-matter in solution 

 can be obtained. It must be recollected that pollution of this nature 

 is quite a different thing, and is easily distinguished, from pollution 

 b^"^ sewage, or by manure spread upon an adjoining garden, to which 

 of course all such shallow wells are liable in an exceptional degree 

 in a district where the subsoil is of such a porous character as it is 

 in the district under consideration. I may also add that the same 

 means, by which I have succeeded in removing all vegetable pollution 

 from water drawn from the shallow well quoted above, are available 

 for the purification of the water drawn from the Middle and Lower 

 Bagshot Strata as well as of water collected by gravitation from 

 open moorlands, or drawn off from natural lake-basins. 



In 1850 the famous engineer Eennie collected a large amount of 

 information on the water-bearing capacity of the Bagshot Sands, and 

 in his Report^ to the Chairman and Directors of the New River 

 Company he states that " water obtained from siliceous sands, such 

 as those which cover the tract referred to, is proved to be of a quality 

 only equalled in excellence by the water derived from mountain 

 granite rocks, or slate rocks, or other surfaces of the primitive for- 

 mations." This statement we have seen to be true onl^'' to a limited 

 extent : it is true for water obtained from ' siliceous sands ' which 

 are free from organic debris, but it is not true for a large portion of 

 the ' siliceous sands ' of the Bagshot Series, since these are highly 

 charged with organic matter of vegetable origin. Further on (p. 5) 

 he states that analyses show that the samples of water obtained from 

 the Bagshot Sands are " the purer, the nearer they are collected to 

 the actual rainfall at the surface." This is now easily accounted for, 

 so far as it is true, by the presence of organic matter in the deeper 

 strata, which we may now consider to have been abundantly proved; 

 but the facts which I have described above show that it is only true 

 for those portions of the district where the old forest-lands have been 

 for some time broken up and brought under cultivation. On p. 7 

 Rennie quotes Mr. Prestwich as an authority for stating that "these 

 sands are not entirely devoid of organic matter." This however is 

 understating the facts, since the evidence adduced in my former 

 paper shows that many of these sands are loaded with it ; and since 

 that was written I have been astonished to see the amount of lignite 

 in a fragmentary state which has been brought up from some exca- 

 vations in the Middle Bagshot Strata. And the lignite is most 

 abundant where the grains of the sand are invariably coated Avith 

 green, olive-green, and black colloid matter. All references to 

 " green silicates," which were supposed to exist in a granular form 



^ '_* Seport off Mr. George Eennie on the Supply of Water to be obtained from the 

 District of Bagshot," London, 1850. 



