98 
WHAT IS IN THE WATEE ? 
sample of air for analysis, altliougli at one time this was not nnfrequently 
done. But although chemical analysis in this case fails, chemists and phy¬ 
siologists are nevertheless enabled, by the application of scientific knowledge, 
to indicate much that contributes in the air to the development and propaga¬ 
tion of disease; and much has been done through the recommendations of 
scientific men towards removing or mitigating the evils of a vitiated atmo¬ 
sphere. 
At the present time, however, the attention of the public is directed, not so 
much to the air they breathe as to the w^ater which enters so largely into 
their food. This being a denser form of matter than air, and the substances 
wfith which it is mostly contaminated being so also, chemical analysis is more 
effectively applied here, and analytical results indicate much more sensible 
differences in different samples of water presented to us in nature than are 
ever found in the atmospheres of difierent localities. The examination by 
chemical analysis of the waters used for domestic purposes is becoming more 
and more generally resorted to, Irrespective of any supposed influence 
wTich the water used with food may have in inducing specific disease, there 
are w^ell-marked differences, as determined by analysis, w^hich indicate the 
extent to which it is applicable for various domestic purposes. 
The purest description of natural water is rain-water, but even this is not 
absolutely pure. The air is w’ashed by the shower that falls, and the surface 
upon which the rain is received and the means by which it is collected add 
something to that which was previously contained in it. Usually, however, 
rain-water, if carefully collected and stored, is very nearly pure, and is never 
likely to contain anything injurious to health. It is perhaps less palatable 
than good spring water, on account of the absence of carbonic acid and car¬ 
bonate of lime, which render spring water brisk and agreeable, but even this 
deficiency might be remedied by a system of aeration. The collection of rain¬ 
water for domestic use has been too much neglected. In towns where the 
atmosphere is much contaminated with smoke and other impurities the rain¬ 
water collected from the housetops could hardly be used without submitting 
it to careful filtration, but by this means it w^ould certainly be made better 
than the river winters so generally employed. There is hardly a house with a 
tiled or slated roof that might not be made, with the aid of filtration, to supply 
water of unexceptionable quality for all purposes w'here pure wmter is required 
by those who live there. In country places this method of providing a good 
w^ater-supply is now deservedly receiving increased attention. It is often the 
only practicable means by which a good and safe supply can be secured. 
Next to rain-water, collected under the most favourable conditions, the 
purest natural water is that of some of the lakes situated in mountainous dis¬ 
tricts. These lakes are, in fact, large reservoirs of rain-water collected from 
the neighbouring mountains, and where the nature of the soil and the geo¬ 
logical formations are favourable very little foreign matter is derived from 
the surfaces over which the water runs into the lakes. Some of the lakes of 
Scotland, the North of England, and Wales, contain very pure water, w^ell 
suited in every respect for domestic use. There is often, however, a little 
colour in lake waters, derived from peaty soil over which the water has run, 
and it may be stated as essential to the purity of lake w^ater, that it should 
not have been collected from any great distance, that the lake should have 
an outlet to the sea, that it should not be situated in a populous district, or 
surrounded by cultivated land. Where these conditions are absent, the water 
of a lake is likely to partake of all the objections that attach to the more im¬ 
pure waters of rivers and even of the sea. 
lliver water, which has hitherto afforded the principal supplies to most 
large towns and populous districts, is much less pure than rain or mountain- 
