conductors
on the armature, or to increase the number of field coils, or both.
That means a larger machine, and a corresponding increase in cost.

In practice, in large plants, with alternating-current machines it has
become usual to mount the field magnets on the shaft, and build the
armature as a stationary ring in whose air space the field coils
revolve. This simplifies the construction of slow-speed, large-output
dynamos. Such a machine, however, is not to be had for the modest
isolated plant of the farmer with his small water-power.

[Illustration: Instantaneous photograph of high-pressure water jet
being quenched by buckets of a tangential wheel]

[Illustration: A tangential wheel, and a dynamo keyed to the same
shaft--the ideal method for generating electricity. The centrifugal
governor is included on the same base]

Dynamos can be designed for almost any waterwheel speed, and, among
small manufacturers especially, there is a disposition to furnish
these special machines at little advance in price over their stock
machines. Frequently it is merely a matter of changing the winding on
a stock machine. The farmer himself, in many cases, can re-wind an old
dynamo to fit the speed requirements of a direct-connected drive if
the difference is not too great. All that would be necessary to
effect this change would be to get the necessary winding data from the
manufacturer himself, and proceed with the winding. This data would
give the gauge of wire and the number of turns required for each spool
of the field magnets; and the gauge of wire and number of turns
required for each slot in the armature. The average boy who has
studied electricity (and there is something about electricity that
makes it closer to the boy's heart than his pet dog) could do this
work. The advantages of direct drive are so many that it should be
used wherever possible.

When direct drive cannot be had, a belt must be used, either from a
main shaft, or a countershaft. The belt must be of liberal size, and
must be of the "endless" variety--with a scarfed joint. Leather belt
lacing, or even the better grades of wire lacing, unless very
carefully used, will prove unsatisfactory. The dynamo feels every
variation in speed, and this is reflected in the lights. There is
nothing quite so annoying as flickering lights. Usually this can be
traced to the belt connections. Leather lacing forms a knot which
causes the lights to flicker at each revolution o