he same
between the divided contact piece, and making a perfect contact. The
switchboard forms one side of a closed wooden case or cupboard, with
sufficient room for a man to enter and adjust the resistances or
switches for each lamp. These are screwed to the inside of the case in
rows, to the number of twenty-five. The greatest care has been taken
in the fixing of the connections to the inside of this case, and no
leading wires of different potential are allowed to cross each other.

[Illustration: FIG. 11A]

The Oerlikon lamp, which is designed to work with constant potential,
is shown partly in section in Fig. 8. There is only one solenoid, A,
through which all the current passes, and whose action is to strike
the arc and maintain the current constant. The soft iron core, C, is
suspended from the inside of the tube, T, in which it has an up and
down movement checked by an air piston in the tube. An end elevation
of the brake wheels and solenoid is given in Fig. 9, where it will be
seen that the spindle carrying these wheels also carries between them
a pinion engaging with the rack rod, R. The top carbon attached to the
rack rod falls by its own weight, and is therefore in contact with the
lower carbon before the lamp is switched in circuit. When this is done
the core is instantly magnetized, and attracted to the soft iron brake
wheels, which it holds firmly. The air cushion in the tube prevents
the core being drawn up until it has fairly gripped the sides of the
wheels. The subsequent raising of the core therefore turns the wheels,
raises the rack rod, and strikes the arc. The feed is operated by the
weakening of the magnetic field of the coil, which causes the core to
lose its grip of the wheels, and allows the top carbon to descend. The
catch, L, Fig. 8, has a lateral play, and serves to engage in the
teeth of the rack rod, so as to prevent its falling when being
trimmed. Each carbon when in position is held against two rectangular
guide bars by the pressure of a wire spring--see figure. In this way
the carbon is pressed against two parallel knife edges, and is
therefore always in true alignment. The action of the lamp is very
simple, the working parts are few and solidly constructed, and the
regulation, as exhibited by the lamps running in the galleries, is
exceptionally steady.

The transmission of power plant consists of two 250 horse power
dynamos--C.E.L. Brown's patent--the generator being driven by a
vert