WHAT IS IN THE WATEE ? 
99 
lake water. E,ivers receive tlieir supplies from different sources,—from sur¬ 
face drainage caused by rains, from the overflowings of lakes, and from 
springs ; but the usually inferior quality of river water is not due to the 
sources from which it is derived, but to the numerous additions of foreign 
matter that are made to it. Pursuing its course for long distances through 
districts often highly cultivated and thickly peopled, the river necessarily be¬ 
comes the receptacle for all sorts of impurities, which are thus quickly re¬ 
moved from places where they would otherwise become a nuisance, and 
ultimately poured into that greatest and most polluted of all lakes, the sea. 
The sewage of towns and villages, the refuse of factories, the drainage of 
cultivated lands, the products of decomposition of animal and vegetable 
matter, are carried down to the river and swept away with the current. 
Eiver water is thus subject to great variations in quality ; it is scarcely ever 
sufficiently pure to justify its use as drinking-water. The increase of popu¬ 
lation and of manufactures, and the extension among the people of habits of 
refinement, have tended to increase the impurity of our rivers. They neces¬ 
sarily partake to a certain extent of the character of sewers, and in a thickly 
l^eopled country, where the inhabitants are accustomed to the refinements of 
a high state of civilization, it would be extremely difficult, if not impossible, 
to obviate this result. 
If the generally received opinion of geologists be correct with reference 
to the original condition of the earth and the successive changes it has 
undergone, all the water that at present covers so large a portion, and has 
penetrated beneath the surface, of our globe, must have been condensed 
from the atmosphere. It has all had one and the same atmospheric origin, 
and it is even now constantly undergoing repurification by a process of dis¬ 
tillation, through atmospheric agency. The comparatively pure conden¬ 
sations from the air, besides supplying our lakes and rivers, moistens the 
otherwise parched soil, and jiercolates through the ground until at last it is 
arrested by impervious strata over which it seeks its level under the influences 
of gravitation, springing out here and there, as irregularities in the surface or 
other physical conditions of the ground, favour such a result. 
Spring water and the water of artificially-formed wells come from the same 
source, and consist essentially of rain water that has percolated through dif¬ 
ferent geological strata, and has thus become impregnated with mineral and 
organic substances, from which its peculiar characters are derived. If the 
ground through which the water has passed be maiden soil, or has received 
only the usual treatment of agriculture, nothing is usually contributed by 
this process to render the water unfit for drinking purposes. Spring and 
well waters generally contain more mineral matter in solution than is present 
in the other waters already noticed, in consequence of the large surfaces 
brought into contact in the percolation ; and as salts of lime and magnesia 
predominate among the mineral constituents, these waters have the character 
of hardness, and are therefore not w^ell suited for washing or for cooking. 
The porous ground through which the water has passed being filled with air, 
such water will be well aerated, and this will contribute to the decomposition 
of any organic matter which the water may have acquired from the upper 
strata of soil. The briskness and generally agreeable taste of spring and 
well waters, which cause them to be preferred for drinking, are due to the 
air, and especially carbonic acid, absorbed from the ground, to their coolness, 
and to the small amount of organic matter present. 
Although the terms spring-water and well-water are often used as synony¬ 
mous, we employ the latter term here to designate an artificial opening into a 
subterranean supply of w ater, while the former term is applied to a natural 
and continuous flow from the surface of the earth. The sources of sunply in 
H 
