n frees its armature, f, and the latter is pulled back by
a spring--a motion that sets in action a small steam engine that closes
the moderator valve. When the contact, a, is again immersed, the
electro, e, attracts its armature, and thus brings the moderator valve
back to its normal position. It is clear that the contact, a, must be
insulated from the ship's side.

Several contacts, a, might be advantageously arranged one above another,
in order to close the moderator valve more or less, according to the
extent of the screw's rise or fall.

* * * * *

MAGNETO-ELECTRIC CROSSING SIGNAL.

We illustrate to-day a new application of electricity to railroad
crossing signaling which the Pennsylvania Steel Company, of Steelton,
Pa., has just perfected. By its operation an isolated highway crossing
in the woods or any lonely place can be made perfectly safe, and that,
too, without the expense of gates and a man to work them or of a
flagman. It is surely a great improvement over the old methods, and it
is likely to have a large sale. In addition to considerations of safety,
possible saving in salaries to railroad companies by its use will be
great. This device is more reliable than a human being, and can make any
crossing safe to which it is applied. Its operation is described as
follows:

[Illustration: FIG. 2.--MAGNETO-ELECTRIC CROSSING SIGNAL]

The illustration shows the device as used on a single track railroad,
where it is so arranged as to be operated only by trains approaching the
crossing (i.e., in the form illustrated, from the right). A similar box
on the other side of the crossing is used for trains approaching in the
other direction. Two plates connected by a link, and pivoted, are placed
alongside of one rail, close enough to it to be depressed by the treads
of the wheels. By another link, one of the plates called the rock plate
(the one to the right) is connected to a rock shaft which extends
through a strong bearing into the heavy iron case or box shown, at a
suitable distance from the rail, within which an electric generator is
placed; the whole being mounted and secured upon the ends of two long
ties framed to receive it.

The action of this rock plate is peculiar. It is pivoted at the rear
end, not to a fixed point, but to a short crank arm, the bearing for
which is inclosed in the small box shown. As the first wheel of a train
which is approaching in the desired di