nd therefore the latter may be run by either machine,
or, in fact, any combination of machines, lamps, and motor be made as
required.

The form of switch made by the Oerlikon Works is illustrated in Fig.
7. Two thick semicircular bands of copper are screwed at one end to
opposite sides of a square block which is turned round by the switch
handle. The block has a projection at each corner, and two strong,
flat, stationary springs are attached to the framework of the switch
and press on opposite sides of the block. The ends of the springs
engage in the projections and prevent the switch being turned round
the wrong way, while the pressure of the springs on opposite sides
forces the copper bands to take up a position exactly in line with the
terminal contacts when the switch is closed, or at right angles to
them when it is opened.

[Illustration: FIG. 4A]

[Illustration: FIGS. 4, 4B and 4C]

Further, each lamp has its own separate adjustable resistance, fuse,
and switch. These are of special construction, combined in one, and
are illustrated in Figs. 4 and 4A; the other figures, 4B and 4C,
showing some of the details of the same. The wires, W W, lead from and
to one lamp. The current enters at one wire, passes through the fuse,
f--Figs. 4C and 4A--down the center of the cylinder to a divided
contact, into which a switch arm can be shot. When this is so, a
connection is made to the upright brass rod, T, which serves to grip
the band, R, passing round the body of the cylinder. The current then
passes through all the turns of wire above the band, and out at the
other terminal. The resistance can be varied by raising or lowering
the band. Fig. 4B shows the manner of tightening the band against the
wires on the cylinder. The upright rod, T, is seen in section, and is
fixed in one position to the frame of the apparatus. Abutting against
this, and working in the block to which the two ends of the band are
screwed, is a thumb screw, S, by turning which the band may be
loosened for adjusting, and tightened when the right position is
found. The cylinder is covered with asbestos sheet, and the wire,
which is of nickel, and measures altogether from 3 to 4 ohms, is wound
helically round this. The switch arm, to which the handle is attached
below, does not itself make and break the circuit, but carries a
spring, as shown, which, when the arm is at the end of its movement,
pulls over the contact lever with a rapid action, shooting t