consists of an ordinary
electro-magnet with a disk in front of its poles. The pile, C, placed
behind the receiver, consists of a piece of carbon, h, held by a
partition, i, and covered with a salt of mercury, and of a plate of
zinc, l, which is held at a distance from the mercurial salt by a
spring, m, fixed to the insulating piece, n.

[Illustration: ANDERS TELEPHONE]

When the button, o, which is a poor conductor, is pressed, the zinc
plate, l, comes into contact with the mercurial salt, and the circuit is
closed through the line wire 1, the pile, the receiver, the transmitter,
and the line wire 2, while when the button is freed the current no
longer passes. The apparatus, then, can serve as a receiver or
transmitter only when the button is pressed.--_Bull. de la Musee de
l'Industrie_.

* * * * *

BROWN'S ELECTRIC SPEED REGULATOR.

When the sea is rough, and the screw leaves the water as a consequence
of the ship's motions, the rotary velocity of the screw and engine
increases to a dangerous degree, because the resistance that the screw
was meeting in the water suddenly disappears. When the screw enters the
water again, the resistance makes itself abruptly felt, and causes
powerful shocks, which put both the screw and engine in danger. Ordinary
regulators are powerless to overcome this trouble, since their
construction is such that they act upon the engine only when the excess
of velocity has already been reached.

Several remedies have been proposed for this danger. For example, use
has been made of a float placed in a channel at the side of the screw,
and which closes the moderator valve by mechanical means or by
electricity when the screw descends too low or rises too high.

[Illustration: BROWN'S ELECTRIC SPEED REGULATOR.]

Mr. Brown's system is based upon a new idea. The apparatus (see figure)
consists of two contacts connected by an electric circuit. One of them,
b, is fixed to the ship in such a way as to be constantly in the water,
while the other, a, corresponds to the position above which the screw
cannot rise without taking on a dangerous velocity. In the normal
situation of the ship, the electric circuit, c (in which circulates a
current produced by a dynamo, d), is closed through the intermedium of
the water, which establishes a connection between the two contacts. When
the contact, a, rises out of the water, the current is interrupted. The
electro, d, the