y repeated in the interlocking of a large number of
signals.

[Illustration: FIG. 94.]

[Illustration: FIG. 95.]

On entering a signal-box a visitor will notice that the levers have
different colours:--_Green_, signifying distant signals; _red_,
signifying home and starting signals; _blue_, signifying facing points;
_black_, signifying trailing points; _white_, signifying spare levers.
These different colours help the signalman to pick out the right levers
easily.

To the front of each lever is attached a small brass tablet bearing
certain numbers; one in large figures on the top, then a line, and other
numbers in small figures beneath. The large number is that of the lever
itself; the others, called _leads_, refer to levers which must be pulled
before that particular lever can be released.

[Illustration: FIG. 96.]

[Illustration: FIG. 97.--Model signal equipment in a signalling school.
(By permission of the "G.W.R. Magazine").]

POINTS.

Mention was made, in connection with the lever, of _points_. Before
going further we will glance at the action of these devices for enabling
a train to run from one set of rails to another. Figs. 98 and 99 show
the points at a simple junction. It will be noticed that the rails of
the line to the left of the points are continued as the outer rails of
the main and branch lines. The inner rails come to a sharp V-point, and
to the left of this are the two short rails which, by means of shifting
portions, decide the direction of a train's travel. In Fig. 98 the main
line is open; in Fig. 99, the branch. The shifting parts are kept
properly spaced by cross bars (or tie-rods), A A.

[Illustration: FIG. 98.--Points open to main line.]

[Illustration: FIG. 99.--Points open to branch line.]

It might be thought that the wheels would bump badly when they reach
the point B, where there is a gap. This is prevented, however, by the
bent ends E E (Fig. 98), on which the tread of the wheel rests until it
has reached some distance along the point of V. The safety rails S R
keep the outer wheel up against its rail until the V has been passed.

POINTS AND SIGNALS IN COMBINATION.

Let us suppose that a train is approaching the junction shown in Figs.
98 and 99 from the left. It is not enough that the driver should know
that the tracks are clear. He must also be assured that the track, main
or branch, as the case may be, along which he has to go, is open; and on
the other hand, if he