In fact, because of danger from flood water and
ice, it is better to locate it in a more protected spot, leading the
water to the wheel by means of a race and flume.

[Illustration: Bird's-eye view of a developed water-power plant]

A typical crib dam, filled with stone, is shown in section in the
diagram, and the half-tone illustration shows such a dam in course of
construction. The first bed of timbers should be laid on hard-pan or
solid rock in the bed of the stream parallel to its flow. The second
course, across the stream, is then begun, being spiked home by means
of rods cut to length and sharpened by the local blacksmith, from
3/4-inch Norway iron. Hemlock logs are suitable for building the crib;
and as the timbers are finally laid, it should be filled in and made
solid with boulders. This filling in should proceed section by
section, as the planking goes forward, otherwise there will be no
escape for the water of the stream, until it rises and spills over
the top timbers. The planking should be of two-inch chestnut, spiked
home with 60 penny wire spikes. When the last section of the crib is
filled with boulders and the water rises, the remaining planks may be
spiked home with the aid of an iron pipe in which to drive the spike
by means of a plunger of iron long enough to reach above the level of
the water. When the planking is completed, the dam should be well
gravelled, to within a foot or two of its crest. Such dams are
substantial, easily made with the aid of unskilled labor, and the
materials are to be had on the average farm with the exception of the
hardware.

[Illustration: Cross-section of a rock and timber dam]

This dam forms a pond from which the race draws its supply of water
for the wheel. It also serves as a spillway over which the surplus
water escapes. The race should enter the pond at some convenient
point, and should be protected at or near its point of entrance by a
bulkhead containing a gate, so that the supply of water may be cut off
from the race and wheel readily. The lay of the land will determine
the length and course of the race. The object of the race is to secure
the required head by carrying a portion of the available water to a
point where it can escape, by a fall of say 30 deg. to the tailrace. It
may be feasible to carry the race in a line almost at right angles to
the stream itself, or, again, it may be necessary to parallel the
stream. If the lay of the land is favorable, t