28 REPORT—1848. 
the surface, and gives a part of this out again in passing through the soil. 
Water becomes hard very rapidly on the surface of some land, and it is 
strange how it adheres to its standard of hardness, remaining for a great part 
of the year the very same. A rapid shower, producing a sudden overflow of © 
a ditch in a field, was found to be composed of water of twelve degrees of 
hardness and sixteen grains of solid matter to a gallon; this same specimen 
also swarming with life. 
I supposed, and others have done so also, that a shower would produce a 
stream of water softer than what slowly trickled through the ground; but on 
examining the water at Longendale in rainy weather it had actually risen two 
degrees. The Thames was also considerably softer in November 1847, after 
some dry weather, than in February 1848 after long rain. At Chelsea, in 
November it was 13°44 degrees of hardness, taking 275 grains of soap test ; 
in February 14°94, taking 302 grains. It would appear that rainy weather 
softened the ground, and so made the matter more soluble, or the winter 
frosts broke up the ground and attained the same end. This latter reason 
is agreeable to the general opinion concerning the use of a frost, and the fact 
may also be taken as a corroboration of the opinion. The hard water will 
of course be better able to feed land with its soluble manures; or, if we 
choose to express it otherwise, the plants will more readily feed, finding the 
food more soluble. 
However true it be that all soil filters water, it is no less true that any ad- 
mixture of clay is detrimental. The clear streams are found in rocky coun- 
tries, and, as was before mentioned and well-known generally, on barren land. 
We have seen that the water of the Thames at London is capable of de- 
composing with the disagreeable products alluded to, and when put in casks 
for sea use we hear of a fermentation, with the formation of nauseous va- 
pours, and of an inflammable gas. We have already seen that Priestley found 
inflammable gas from organic matter decomposing in water, and, in fact, it 
is a thing universally observed. Priestley said, however, what is not so much 
observed, that the air from the decomposition of a cabbage in the dark 
was inflammable, whereas that in the sun produced very little inflammable 
air, and was not so offensive in smell. The fermentation of water may in 
fact be looked upon as a simple proof of great organic impurity. Organic 
matter will decompose either by going into inorganic gases, as in the dark, 
or into organized bodies of another description, if there be light to favour 
growth. These considerations bring us to the mode of storing water, and 
of supplying water to houses. If there be a large supply of water in a 
reservoir, it will, if impure, clear itself by vegetation, according to what we 
have seen by experiment, and as is seen in nature. In this case a reservoir 
must not be underground but in the light; strong light and great warmth 
seem too much to assist chemical solution, the reservoirs should therefore 
not be so shallow as to allow this. However, there are probably few cases. 
where water is to be so long stored; as to the usual cases, it may be said, 
that unless long storage is allowed, it is better that there should be as little — 
as possible, unless the water is to be filtered before delivery. The reason 
of this is, that the course of purification of impure water is the worst state 
of all; even filtered water will not bear standing, because it also tends to 
purify itself still more by giving out in some form or other all its organic 
contents; and it is remarkable how the apparently purest water will deposit — 
impure matter, 
The same thing may be said of water stored onasmaller scale, as for private — 
houses, there is no way of keeping it clear. If kept dark and cool the 
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