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
vertical compound condensing engine of the same power, running at 180
revolutions. The dynamo generator is a four-pole 600 volt direct
current machine, series wound, and may be distinguished in the
engraving next to the switch board; while the motor receiver
connected to it, and erected in another portion of the Swiss section,
is of exactly the same size and type. The field, which is hexagonal in
shape, is cast in two pieces, bolted together horizontally, the
cross-sectional area of iron being 170 square inches.
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