rozen up through the entire winter following.

Such simple methods also fail when the supply of water is not adequate,
since, in order to secure a large quantity from a stream whose flow is
periodic and irregular, some storage must be provided, and storage
usually requires more or less elaborate construction work at the
reservoir. Another reason for more elaborate construction at a spring is
to prevent surface contamination, and it is always desirable to roof
over a spring in order to protect it from surface flows. The writer has
seen, as an example of objectionable construction, a spring in the
bottom of a ravine or gully down which, in time of rain, torrents of
water passed, although in a dry season the spring was the only sign of
water in the vicinity. It could not but happen that this torrent of
water, which carried all kinds of pollution from the road above,
practically washed through the spring, destroying its good quality. In
such a case, another channel for the gulley water ought to have been
made, or else the spring dug out and roofed over, so that the torrential
water could pass above it.

In other cases, the spring is found at the lowest point in a general
depression, so that, while no stream passes through the spring, the
spring is a catch-all for the surface drainage in the vicinity. In such
cases the water should be protected by a bank of earth around the
spring, behind which the drainage should be led off through a special
pipe line if necessary.

_Spring reservoirs._

In protecting the spring and in building up around it in order to put it
underground, concrete is the most suitable material, although a large
sewer pipe or a heavy cask or barrel will answer the purpose. It is
usually sufficient to dig out the spring to a depth of four or five
feet, and with a pump it is possible to keep the water down, so that the
concrete walls may be laid. In building these walls, it is important to
notice from which side the spring water comes, and on that side holes
should be left in the wall. These openings may properly be connected
with agricultural tile drains laid out from the spring in different
directions, serving both to drain the ground and to add volume to the
spring. It is often possible instead of pumping out water during
construction to drain a spring temporarily, in places where the ground
slopes rapidly, by carrying out a drainpipe from the lowest level; this
drain is to be later stopped up.

The s