REPORT OF MR. ROBERT B. LINES.
459
As wheel IV. revolves, therefore, in the direction of the arrow, the upright z is raised, and the semaphore lowered to "arrest.” At the end of a half turn, however, the eccentric on wheel IV. has raised the lever a h to its original position. There being no longer any current passing through the electromagnet /(for, as I have said, the slightest turn of the crank is sufficient to set the machinery in motion), the spring o lifts the armature m, and the arm b again supports the lever a h at the point a.
An instant after, the bent arm of the catch g, which has been kept in its raised position by a second eccentric on wheel IV., falls into the notch. The lower, or straight arm of y, is thus raised, intercepts the wheel I and blocks the machinery. The joint X is now above instead of below the wheel IV., and the semaphore is maintained at the position of arrest.
It is evident that {mother current of electricity will again release the clock-work, and the wheels moving again in the same direction, will bring the apparatus back to the position shown in the diagram, and change once more the position of the semaphore.
The number of times this can be repeated, depends, of course, upon the distance which the weight has to descend before " running down.” In almost all of the siguals yet constructed, the clock-work has been placed by Mr. Hohe- negger at the top of the apparatus, instead of near the base, as here represented. The construction here shown has been lately adopted on account of the difficulty in winding up the apparatus at such a height, but the change has, of course, rendered more frequent attention necessary.
The use of two wires in this signal, which on a short line Would not be a matter of much moment, on longer circuits would, of course, add greatly to the expense of the apparatus. Its object is to avoid the giving of false signals by lightning or " earth currents,” to which the system would be liable if the earth formed part of the circuit. I do not think this danger sufficient, however, to justify, or rather to require the use of a second wire in case of the signal being employed at a considerable distance.
It will be seen by reference to Fig. C, that a third wire is employed for what I suppose must still be called the " control,”