Rev. A. Irving—Water Supply from Bagshot Sands. 407 
for some time, gives up the greater part of its crenic and apocrenic 
acids, which form corresponding soluble salts of the alkali-metals ; 
and from these the acids are easily precipitated with acetate of 
copper, according to the method described in Watts’ Dictionary. 
It may also be stated here that further evidence of their existence 
as definite acids is seen in the fact that the crenate of copper, which 
is precipitated, can be dissolved slowly in a hot solution of carbonate 
of soda or potash; the CO, goes off with effervescence, and from the 
alkaline solution thus obtained the crenic acid is again precipitated 
as a definite salt of copper in the same condition as that in which 
it existed before solution. 
This replacement of CO, by these acids also goes to show that 
chemically they are more powerful than carbonic acid, and may be 
regarded therefore by the geologist as possessing even greater power 
than that well-known acid as a metamorphic agent, though their 
action must be obviously more limited in its range in this respect. 
Boutigny has shown that the medicinal waters of Forges-les-Haux, 
which are derived partly from a peaty stratum, contain crenic 
and apocrenic acids as soluble salts, and, on this account, deposit 
an insoluble ferric compound on exposure to the air, just as the 
waters drawn from our middle and lower Bagshot Sands do.’ I 
have heard it asserted by professional engineers, who have been 
much occupied with questions of water-supply, that the green colour 
of the middle and lower Bagshot Sands must contribute to the 
purity of the water which they furnish, on the supposition that this 
green matter was iron in a low state of oxidation. This however 
is a mistake ; for (1) the green matter is the result of vegetable 
contamination, (2) iron in a ‘low state of oxidation’ is rather a 
reducing than oxidizing agent, and could hardly therefore act in 
the way which these gentlemen seemed to suppose. 
There can be no doubt that the ordinary methods resorted to by 
professional analysts leave us still in the dark as to certain qualities 
of many waters which are pronounced wholesome and ‘potable,’ ? 
though some advances have been made quite recently in these 
matters. It appears that the analyst considers it beyond his pro- 
vince to investigate the nature of the pollution by “ vegetable matter”’ 
which is sometimes seen noted in analytic returns. It may be that 
in some of its forms such vegetable pollution of water does no great 
harm, yet no one would if he knew it drink water drained from a 
morass. On this point ordinary common sense leads the population 
of country districts to distinguish and avoid water thus contaminated. 
Nothing is more common, for example, in the experience of Alpine 
tourists, then to find themselves, when oppressed with thirst in the 
high Alps, warned against drinking from a spring of clear, and 
apparently pure, water. The natives know by experience its 
1 Vide Watts’ Dictionary of Chemistry, 2nd Supplement. See also Julien (Journ. 
Am. Assoc. Sci. 1879, pp. 336, 337) for a long list of mineral springs in which these 
acids have been found. 
2 Vide paper by C. W. Folkard on ‘‘The Analysis of Potable Water,’’ in the 
Proc. Inst. Civil Engineers, January 24, 1882. 
