730 
Water in Relation to Wealth and Disease. 
Manchester Water. 
Silica ..... 
Grains per 
gallon 
Carbonate of lime 
. 1-70 
Sulphate of magnesia . 
• . • • 
. 1-66 
Chloride of sodium 
. 
. 0-91 
Total 
. 4-57 
floLHHRTH Water. 
Sulphate of lime . 
Grains per 
gallon 
Sulphate of magnesia , 
• • • • 
. 0G 
Chloride of sodium 
• • • • 
. 0-8 
Nitrate of soda or potash . 
. 
. 0-2 
Total i 
. 2-4 
In consequence of the small quantity of lime they contain 
these two waters are very soft. 
In its passage through the earth, water not only dissolves 
out one or more of the saline constituents, but in passing 
through the deeper strata the suspended particles gathered 
from the surface and subsoils are filtered out of it and left 
behind, so that a process of exchange is continually going on 
between the soil water and the underground formation through 
which it percolates. 
The water dissolves and carries away portions of the rocks, 
while they in return arrest and retain the solid particles, 
organic and mineral, which are suspended in it. This is the 
natural system of purification, but it does not end here. Porous 
strata, sand and gravel in particular, contain a considerable 
quantity of oxygen, which burns up all the organic filth, and 
converts it into harmless compounds. Purification is thus 
carried on and rendered complete, the more so the deeper the 
filtering bed through which the water has to pass. For this 
reason the water of deep wells and springs is much purer than 
that of shallow ones. 
By the presence of such salts as appear in the above analyses 
some waters acquire important properties, and are rendered 
valuable by their medicinal action. In ordinary supplies, how- 
ever, the chief saline constituents of interest are those of lime, 
especially the carbonate of lime (chalk), and sulphate of lime 
(gypsum). It is to these that water owes the quality of hard- 
ness. When salts of lime exist in considerable amount, health 
is liable to impairment in various ways. Among other things, 
horses drinking hard water suffer from derangement of the 
organs of digestion and from a liability to attacks of colic and 
other intestinal disorders. The skin of such animals loses its 
