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EXPOSITION AT VIENNA.
Plate ix. small box upon the table, and can only be
B moved by pressure of the finger) in
order to complete the circuit to the semaphore.
The action of the apparatus is as follows : By depressing the button a and turning the crank, a current is made to pass out on the line ?, through the magnet in the semaphore, returning by l to the inductor.
On the current reaching the magnet (f Plate IX. B), the latter attracts the armature rn, which until then has been held in position by the tension of the spring o. Near the fulcrum of the armature are two arms, b and c, the former of which sustains the lever a h, which is hung at the pointy. As soon as the armature m is attracted by the electro-magnet , however, the support of the arm b is withdrawn and the lever a h falls into the fork of b and c, the projection on the under side striking upon the eccentric on wheel IV. below. An extension to the right of the fulcrum p, forming the short arm of the lever, lifts the catch g , the lower arm of which has kept the wheel I. in arrest. The catch being thus released, the weight sets the clockwork of the apparatus in motion, the course of the wheels being indicated by the direction of the arrows.
In Plate IX. B the signal is at line clear, the arm being raised. I represents the axis of the arm to which the latter, as well as the lever k, is immovably fixed. The lever k is attached by a movable joint to the upright z, which is in its turn attached by a movable joint to the lever n. A third movable joint attaches this to the lower part of z, which is extended to x. At x another lever extends and is firmly attached to the axis of wheel IV.
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