TELEGRAPH. I. OCEAN TELEGRAPHY.—During the last few years few radical innova tions in ocean telegraphy have been suggested, while practically none of fundamental im portance have been introduced. There has, however, been marked improvement in details, and many valuable refinements have added to the speed and accuracy of working.
A Selenium Cable Recorder. —The currents employed in submarine telegraphy are so min ute that the method first employed in receiving messages was that of the deflections of a very delicate mirror galvanometer. Later, Sir William Thomson introduced his siphon recorder, which leaves a permanent record, consisting of a continnous curve of varying amplitude, the reading of which, however, requires considerable practice. With the idea of obviating this difficulty. Eugene Baron, of Tannd-Szyll, Germany, has recently devised a form of recorder in which the record is considerably simplified. and approaches more nearly to the 3lorse characters. Broadly stated, the de letting coil of the ordinary siphon recorder is made to change the position of a light screen, which, moving before two small slits, admits light to and shuts it off from two selenium cells, which then act in the manner described below.
The accompanying illustrations show the details of the apparatus. The box, K, Figs. 1 and 2. is divided into two compartments, the first of which contains the electromagnetic part of the relay and the selenium cells. This disposition is not essential, however, as they can be removed to any desirable place, and the recording apparatus proper need only be in the operating room. The second compartment contains a bright source of light, such as an incandescent lamp, F, Fig. 8. The dividing wall between the two, W. has two slits, through which the light enters when permitted to by the screen, V. The relay consists. as stated above, of the siphon recorder coil, r, placed in the magnetic field of the magnets, N S, and deflected in either direction, according to the direction of the currents in the cable. The coil carries a downward projection in the shape of a triangular prism, V, Figs. 1 and 3.
When the latter is in its central position it covers both slits, e, and and prevents the light from passing either one. A current passing through the coil deflects the latter correspond ingly, and with it the triangular screen, which then permits the light to pass in the same side, as shown, in the direction, F J, Fig.:. After passing the slits, the light is concen trated on the selenium cells. ZI Z2 by the lenses. L, L. Fig. 2.
Light falling on the cells reduces their resistance. as is well known, and the two local bat teries being in circuit with the cells. Z, the current is varied accordingly. The ment of the recording apparatus is shown diagrammatically in Fig. 2. M, and It are two pow erful horseshoe magnets. the poles of like name being diagonally opl:osite each other. Between the poles of these magnets there is pivoted a bar magnet. A, supported by the spindle. X. This polarized armature can be regulated to a central position by the springs„ A, and the coils, a, n, of very fine wire, are included in the local circuits. The poles, a, s„ act, the one attractively, the other repulsively, upon the armature ; s, a, act similarly. A small dif ference in the strength of these four poles causes a deflection of the armature. It is apparent that as light is admitted to either cells, the armature, will he deflected in one direction or the other, and the armature can be made to record these movements, either directly or through the medium of another recording apparatus, by the eiosing of an auxiliary local circuit.
The Cultriss Siphon Vibrator for Ocean Cables.—The use of static electricity to vibrate the siphon, with the object of preventing friction at the marking point of Sir William Thomson's siphon recorder, has always been the one defect in this otherwise most. perfect and beautiful instrument ; for, as is well-known. in damp weather, static electricity is difficult to produce and weli-nigh impossible to control.