equires some sort of bucket
which will dig automatically under water and has not been therefore a
customary method except for large excavations where machinery can be
installed. There is no reason, however, why the method might not be used
for a single house.

[Illustration: FIG. 28.--A well that will catch surface waste.]

In whatever way the well is dug, one point in the construction that
needs to be emphasized is that the wall should be well cemented
together, beginning about six feet below the surface and reaching up to
a point at least one foot above the surface. This is to prevent
pollution from the surface gaining direct access to the well, and if
this cementing is well done for the distance named, it is not likely
that any surface pollution in the vicinity of the well could ever damage
the water. Figure 28 shows the section of a well where no such
precautions have been taken, and it is evident that not only surface
wash, but subsurface pollution may readily contaminate the water. Figure
29 (after Imbeaux), on the other hand, shows a shallow well properly
protected by a good wall and water-tight cover. Figure 30 shows a
photograph also of this latter type of well. Even if a cesspool or privy
is located dangerously near the well, in the second case the fact that
the contaminating influence must pass downward through at least six feet
of soil before it can enter the well is a guarantee that the danger is
reduced to the smallest possible terms.

[Illustration: FIG. 29.--A well properly protected.]

_Deep wells._

Deep wells are of the same general character as shallow wells. Usually,
the ground on which the rainfall occurs is more distant, so that the
source of the water is often unknown, and usually, also, the stratum
from which the water comes is overlaid by an impervious one.

[Illustration: FIG. 30.--A properly protected well.]

It often happens that there are several layers of water or of
water-bearing strata alternating with more or less impervious strata,
and that wells might be so dug as to take water from any one of them.
Indeed, not infrequently in driving down a pipe to reach water, a fairly
satisfactory quantity is obtained at a certain level, and then, in
order to increase the supply, the pipe is driven further, shutting off
the first supply and reaching some other, less abundant.

Deep wells are reached usually by wrought-iron pipe driven into the
ground. Sometimes this is done by taking a one