that this drain
may not become choked, at suitable intervals, in the length of the track,
sump holes are formed as illustrated in diagram, Fig. 4 These sump holes
have a well for the accumulation of mud, and are also connected with the
main street drain, so that water can freely pass away. The hand holes
afford facility for easily removing the dirt.

In a complete track these hand holes would occasionally be wider than shown
here, for the purpose of removing or fixing the collector, Fig. 5, which
consists of two sets of spirally fluted rollers free to revolve upon
spindles, which are held by knuckle-joints drawn together by spiral
springs; by this means the pressure of the rollers against the inside of
the tube is constantly maintained, and should any obstruction occur in the
tube the spiral flute causes it to revolve, thus automatically cleansing
the tubes.

[Illustration: FIG. 4]

The collector is provided with two steel plates, which pass through the
slit in the center rail; the lower ends of these plates are clamped by the
upper frame of the collector, insulating material being interposed, and the
upper ends are held in two iron cheeks. Between these steel plates
insulated copper strips are held, electrically connected with the collector
and with the adjustable clip mounted upon the iron cheeks; this clip holds
the terminal on the end of the wire (leading to the motor) firmly enough
for use, the cheeks being also provided with studs for the attachment of
leather straps hooked on to the framework of the car, one for the forward
and one for backward movement of the collector. These straps are strong
enough for the ordinary haulage of the collector, and for the removal of
pebbles and dirt that may get into the slit; but should any absolute block
occur then they break and the terminal is withdrawn from the clip; the
electric contact being thereby broken the car stops, the obstruction can
then be removed and the collector reconnected without damage and with
little delay.

[Illustration: FIG. 5]

In order to secure continuity of the center rail throughout the length of
the track, and still provide for the removal of the collector at frequent
intervals, the framework of the collector is so made that, by slackening
the side-bolts, the steel plates can be drawn upward and the collector
itself withdrawn sideways through the hand holes, one of the half-tubes
being removed for the purpose.

Fig. 6 illustrates another arr