CHEMISTRY AND PHYSICS. 55 
self or his neighbor. Modern man, on the contrary, is a fixture in one location, 
and this, together with his gregarious habits, tends to a concentration of the 
waste products of his own activity, a system of life that we boastfully call civiliza- 
tion. This brings evil through rendering these common heritages unsafe for use. 
The very best and keenest intelligence of the race has been and is being brought 
to bear on the problems that have arisen under these conditions. Much has 
been learned of the means to be employed to avoid or lessen its effects, but there 
are still many things that are seen but imperfectly—many problems still un- 
solved. It is the province of this paper to briefly summarize the condition of our 
knowledge with reference to one of these elements, viz., water. In view of the 
fact that nearly five-sixths of the human body is composed of water, and that five 
or six pints are required daily for its sustenance, it would seem that every intelli- 
gent person possessing a lively instinct of self-preservation should desire to be 
possessed of all possible knowledge relating to its quality and the matters carried 
by it. 
The sources from which supplies are obtained are four: From cisterns that 
catch and store the rainfall from roofs; shallow wells for the supply of isolated 
dwellings, or, when built larger or coupled together, for the supply of towns; deep 
wells, furnishing artesian water; rivers, or lakes and ponds, either natural or 
artificial. The common source is the rainfall, and it may clear the discussion if 
we trace this through its various stages, before it appears in a private or public 
supply. The water vapor that has arisen from the surface of land or ocean is 
condensed and falls as rain, washing the air of its mineral and organic dust, and 
absorbing also soluble gases, if any are present —ammonia, carbon dioxid, sul- 
phur oxids,etc. Even the rainfall, then, is not pure water, and when gathered from 
city roofs itis further made more impure by the roof washings; so that cisterns often 
contain a considerable quantity of mineral and organic matter, either dissolved in 
the water or found at the bottom in a putrescent mass. In the smaller towns it 
is not likely that the amount and character of such impurity will be detrimental 
to the health of those that use the water, if cisterns are kept reasonably clean; 
but in larger places, where dust and smoke are much more abundant, such water 
may be at least objectionable to the senses of sight and smell, if not absolutely 
harmful. 
When the rain falls on the ground it gives up to the vegetation its ammonia, 
and in return takes up from the soluble rocks certain of their salts and washes 
from the soil its earthy or organic dust, thus becoming richer in carbon dioxide 
and albuminoid ammonia, and with increased solvent power. Flowing from the 
highlands to the regions of forest and plain, various organic substances are ex- 
tracted which add to the impurity of the water, and often give it a decided color. 
An undulating country, underlaid by sandstone formations and covered by a suc- 
cession of forest and meadow and peaty bog, furnishes a brown or amber water, 
the color being derived chiefly from decomposed and caramelized carbonaceous 
matter. The water flowing from a limestone region, where the rocks are of a 
more soluble character and have given up some of their elements, is more apt to 
be colorless, though harder than the brown waters, and often containing as much, 
or more, organic matter. The rills and rivulets run together to form the larger 
streams, adding constantly to their burden of suspended or dissolved matter, both 
mineral and organic. The former kind of these impurities does not trouble the 
sanitarian when dealing with a surface-water, unless the matter is present in an 
excessive amount, as is the case with some of our larger western rivers. And 
here the difficulty is one connected with the appearance of the water or the dis- 
agreableness of its use, rather than on account of any direct bearing that the 
