408 Rev. A. Irving— Water Supply from Bagshot Sands. 
unwholesome character. Such water can only be contaminated by 
vegetable matter; for, except in the immediate proximity of a col- 
lection of cattle-stalls, there is no chance of contamination of the 
water from animal sources. Such springs may be rendered impure 
either (1) from surface causes, where the water has drained wholly 
or partly from a morass, as often happens where moraine material 
or other forms of mountain-débris hold water, or (2) from lignite, 
peat, or vegetable matter in other stages of decomposition, which may 
have been imbedded in the strata from which the spring issues. 
Just as ordinary human intelligence is to the Alpine peasant a 
guide in these matters, so it is to the peasantry of this district of 
Sandhurst. I have been at the pains to collect information on some 
oO wells in the district, and have by this means arrived at some in- 
teresting results as bearing upon water-supply. 
It is well known to geologists that the Bagshot strata admit of 
a triad division, as was shown some years ago by Prof. Prestwich ; 
but the great difference between the actual character of the Upper 
Bagshot Sands and that of the Middle and Lower Bagshot Sands and 
Clays, is not so generally recognized. These differences are mainly: 
(a) the total absence of any continuous clay strata in the Upper 
Bagshot series, while the Middle and Lower series contain several 
persistent clay seams, which extend for miles through the country. 
(6) A bright buff-yellow colour is generally prevalent in the sands 
of the Upper series, the shade of colour generally approaching that 
of weathered limonite, except where, in parts subjacent to the por- 
tions of the surface of the country which have been the seat of the 
growth of marsh vegetation for ages, the colour is deepened 
into an ochreous red, which analysis shows to be due mainly to 
the presence of crenate and apocrenate of iron. The sands of the 
Upper series may therefore be considered as abounding in hydrated 
peroxide of iron, while from their distinctly marine origin! they 
are free from any admixture of vegetable matter. The iron is easily 
separated by solution in hot hydrochloric acid, from which it can be 
reprecipitated by soda. 
The Middle and Lower Bagshot sands are of a less pure character. 
A bright ferruginous sand cannot be said to exist in either of these 
two divisions of the series. This statement is based mainly upon 
an examination of the specimens preserved some 20: years ago, 
when the deep well was sunk at Wellington College. This 
section I have more fully described in the paper to which reference 
was made above: it need not then detain us any longer, except to 
note that as soon as a well penetrates a certain clay-seam (9 feet 
thick in our well-section), no more bright ferruginous sands are 
reached ; but in place of them we find a series of impure green 
sands, the green colour in some cases being of as dark a shade as 
that of green bottle-glass. Such green sands prevail for about 40 
feet down. Then we have a series of clays, some of them “ pipe- 
clays,” for about 20 feet. Beneath these again the impure green 
_| Vide paper by H. D. Monckton, Esq., F.G.S., in Quart. Journ. Geol. Soc., 
No. 164, tor a considerable list of marine forms preserved in the Upper Bagshots. 
