m of this rod and gears with a
similar wheel on the shaft of the driving motor (not shown). Suspended from
the broader sides of S are the two flexible arms D, each carrying a brass
ball T. These balls are not fastened to the arms, but can slide up and
down, being held in position by the wire springs M, one end of each spring
being fastened to the screws C. These screws work in a slot cut in the
upper part of S, and are connected to the adjusting screw E. When E is
turned the screws are raised or lowered accordingly, and also the balls on
the arms D.

Fastened to the arms are two brushes of tow B, and these revolve inside but
just clearing the inner surface of the steel ring Z. Upon the motor speed
increasing above the normal the arms D, and consequently the balls T, swing
out, making a larger circle, causing the brushes B to press against the
steel ring Z, setting up friction which, however, is reduced as soon as the
motor regains its ordinary working speed. By careful adjustment the speed
of the motors can be kept perfectly constant. The object of having the
balls T adjustable on D, is to provide a means of altering the motor speed,
as the lower the balls on D the slower the mechanism runs, and _vice
versa_. {68}

[Illustration]

A simple and effective speed regulator devised by the writer is given in
drawings 33 and 34. It comprises two parts, A and B, the part A being
connected to the driving motor, and the part B working independently. The
independent portion B consists of an ordinary clock movement M, a steel
spindle J being geared to one of the slower moving wheels, so that it makes
just one revolution in two seconds. This spindle, which runs in two coned
bearings, carries at its outer end a light [Illustration] pointer D, about
two inches long, to the underside of which is fastened the thin brass
contact spring S, which presses lightly upon the ebonite ring N. {69} The
portion A comprises a spindle, pointer, and contact spring similar to those
employed in B, the spindle J' being geared to the driving motor by means of
F, so that the pointer D' makes a little more than one revolution in two
seconds. By means of a special form of brake on the driving motor, the
speed is reduced, so that both pointers travel at the same rate, viz. one
revolution in two seconds. By careful adjustment the two pointers can be
made to revolve in synchronism,[9] and when this is obtained the contact
springs S, S', pass over the contact