a few points. The centre rail should on the curves
also be 3/8 inch deep, and raised slightly above the bed so as to project
above the wheel rails. The method already described of bonding at joints
will serve equally well on curves. If the outer rail is super-elevated
slightly, there will be less tendency for the rolling stock to jump the
track when rounding the curve.

When the rails are in place the boards may be cut with a pad-saw to curves
corresponding with the breadth of the track on the straight. If the boards
incline to warp, screw some pieces of 1/8-inch strip iron to the under side
across the grain, sinking the iron in flush with the wood.

The brass strip for the rails costs about one penny per foot run. Iron
strip is much cheaper, but if it rusts, as it is very likely to do, the
contact places will need constant brightening.

Points.--Fig. 45 shows the manner of laying out a set of points, and
connecting up the rails. The outside wheel rails, it will be seen, are
continuous, and switching is effected by altering the position of the
moving tongues, pivoted at PP, by means of the rod R, which passes through
a hole in the continuous rail to a lever or motor of the same reversible
type as is used for the locomotive. If a motor is employed, R should be
joined to a crank pin on the large driven cog--corresponding to that
affixed to the driving wheel (Fig. 47)--by a short rod. The pin is situated
at such a distance from the axle of the cog wheel that a quarter of a
revolution suffices to move the points over. The points motor must, of
course, have its separate connections with the "central station." To show
how the points lie, the rod R also operates a semaphore with a double arm
(Fig. 46), one end of which is depressed--indicating that the track on that
side is open--when the other is horizontal, indicating "blocked." The arms
point across the track.

[Illustration: FIG. 45.--Points for electric railway.]

Details.--The tongues must be bevelled off to a point on the sides
respectively nearest to the continuous rails. The parts AA are bent out at
the ends to make guides, which, in combination with the safety rails, will
prevent the wheels jumping the track. Care should be taken to insulate
centre rail connecting wires where they pass through or under the wheel
rails.

It is advisable to lay out a set of points, together with motor and
signals, on a separate board.

[Illustration: Fig. 46.--Double-armed sign