e of danger in
water is always human or animal pollution. Occasionally we find water
which is bad to drink on account of minerals dissolved on its way through
the ground or on account of passage through lead pipes, but the danger is
never from ordinary decomposing vegetable matter. If you have to choose
between a bright, clear stream which may be polluted at some point above,
and a pond full of dead leaves and peaty matter, but which you can inspect
all around and find free from contamination, choose the pond. Even in the
woods it is not easy to find surface waters that are surely protected, and
streams particularly are dangerous sources of water supply. We have now
got rid of the idea that running water purifies itself. It is standing
water which purifies itself, if anything, for in stagnation there is much
more chance for the disease germs to die out. Better than either a pond or
stream, unless you can carry out a rather careful exploration of their
surroundings, is ground water from a well or spring; though that again is
not necessarily safe. If the well is in good sandy soil with no cracks or
fissures, even water that has been polluted may be well purified and made
safe to drink. In a clayey or rocky region, on the other hand,
contaminating material may travel for considerable distance under ground.
Even if your well is protected below, a very important point to look after
is the pollution from the surface. I believe more cases of typhoid fever
from wells are due to surface pollution than to the character of the water
itself. This is a danger which can, of course, be done away with by
protection of the well from surface drainage, by seeing that the surface
wash is not allowed to drain toward it and that it is protected by a tight
covering from the entrance of its own waste water. If good water cannot be
secured in any of these ways, the water must be purified. It has been said
that what we desire in water supply is innocence and not repentance; but
if you cannot get pristine innocence, you can, at least, secure works meet
for repentance and make the water safe, by filtering through either a
Pasteur or a Berkefeld filter--either of those filters will take out
bacteria, while no other filters that I know of will or by various
chemical disinfectants, not any of them very satisfactory--or, best of
all, by boiling, which will surely destroy all disease germs."

Indians had a way of purifying water from a pond or swamp by d