Air and sunshine having been assured for all parts of the house in daily
use, the next question must be an unfailing and full supply of pure water.
"Dig a well, or build near a spring," say the builders; and the well is
dug, or the spring tapped, under the general supposition that water is
clean and pure, simply because it is water, while the surroundings of
either spring or well are unnoticed. Drainage is so comparatively new a
question, that only the most enlightened portions of the country consider
its bearings; and the large majority of people all over the land not only
do not know the interests involved in it, but would resent as a personal
slight any hint that their own water-supply might be affected by deficient
drainage.

Pure water is simply oxygen and hydrogen, eight-ninths being oxygen and
but one-ninth hydrogen; the latter gas, if pure, having, like oxygen,
neither taste nor smell. Rain-water is the purest type; and, if collected
in open vessels as it falls, is necessarily free from any possible taint
(except at the very first of a rain, when it washes down considerable
floating impurity from the atmosphere, especially in cities). This mode
being for obvious reasons impracticable, cisterns are made, and rain
conducted to them through pipes leading from the roof. The water has thus
taken up all the dust, soot, and other impurities found upon the roof,
and, unless filtered, can not be considered desirable drink. The best
cistern will include a filter of some sort, and this is accomplished in
two ways. Either the cistern is divided into two parts, the water being
received on one side, and allowed to slowly filter through a wall of
porous brick, regarded by many as an amply sufficient means of
purification; or a more elaborate form is used, the division in such case
being into upper and under compartments, the upper one containing the
usual filter of iron, charcoal, sponge, and gravel or sand. If this water
has a free current of air passing over it, it will acquire more sparkle