REPORT OF MR. ROBERT B. LINES.
467
■which operates the small signal, is broken at z, notwithstanding it was at the same instant closed at x.
At the same time the magnet M turns the semaphore disc D in the direction shown by the arrow. Just before the disc D completes its movement, and after the white signal has been fully exhibited, a projection at o, on the lever L, comes in contact with a corresponding projection on the circuit-charger 4 and lifts it up, breaking the previously existing electrical contact at n. This cuts the battery' current olf from the magnet M and instantly transfers it to the locking magnet N. This occurs just as the soft iron armature Q on the disc comes in contact with N, and the latter beiim now stroimlv masr- netic, seizes Q with great force and locks the signal disc firmly in its new position. The magnet N is, however, wound with a much finer wire than M, and the insertion of this great amount of extra resistance in the circuit weakens it to less than half its original strength in the relay R. When this occurs, the spring S, which is adjusted with a strong tension, pulls the lever J away from the relay-magnet until it is itself arrested by the stop z. At this juncture the local circuit is completed through wires 8,9, and 10, and levers B mid J, and the station-signal turns to white also, respecting the movement of the semaphore.
It will be seen that the system of Mr. Pope, which requires a permanent current to maintain the semaphore at " line clear,” entirely avoids the danger from atmospheric currents, which seems to have been a bugbear of European systems, and that it fulfils as completely as possible the cardinal condition of Mr. Preece, that " any derangement of the apparatus, or the accidental delivery of a false signal, should at once indicate danger and produce safety.”
Were it required to deliver the signal from a passing train,
the object might perhaps be accomplished by substituting for
the mao-net M a mao-net such as that used for the automatic • © ©
whistle (Plate VIII.), the armature of which should be attracted by the combined force of the permanently magnetized cores and of a current of electricity sent in one direction, and again repelled (on the arrival of the train at a second contact where the semaphore should be changed) by the combined force of the spring and a current sent in the opposite direction.
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