.S7A 1 H'JLL/AM S/EMKXS, J-.K.S. IQJ 



kinks. But it appears, from experiments made at Camdeii Town 

 I iy the Joint Committee on the Construction of Submarine Tele- 

 LTujih Cables (Appendix No. 9 of their Report), that copper wire 

 cannot be elongated more than 2 per cent, without receiving a per 

 manent set. It is also a well-ascertained fact, that when telegraph 

 OUT has been stretched at any time beyond the limits of elas- 

 ticity of the copper, the latter being henceforth too long for the 

 more elastic covering, will tend to assume a serpentine form, and 

 will push its way through the insulating material by slow degrees, 

 particularly in places where short bends, or kinks, occur. 



Based upon these views, the author designed a sheathing of the 

 following description : The conducting strand of copper wires con- 

 sists of seven comparatively strong and six thinner wires, which 

 latter fall into the spiral grooves between the fonner, and produce 

 a near approach to the cylindrical form, presenting the least sur- 

 face, for a given conducting area. The small remaining interstices 

 are filled up with Chatterton's, or some other, compound before the 

 conductor is covered, first with pure india rubber, in two layers, by 

 the process before described. The india-rubber-covered conductor 

 is carefully tested, and thereupon covered with gutta percha by the 

 ordinary die ; Chatterton's compound being used to solder the two 

 materials. The insulated conductor, or core, thus formed, is passed 

 in the sheathing works through a series of three machines in close 

 succession. In passing through the hollow spindle of the first 

 machine, a close spiral covering of hemp, previously saturated with 

 Stockholm tar, is applied, in such a way that each string is, and 

 remains, under a given strain, which may be adjusted by friction- 

 brakes. The second machine is similar in construction to the first, 

 but it supplies a second covering of hemp, wound in the opposite 

 direction to the first. The rope thus formed passes next through a 

 .stationary clip, with longitudinal grooves, to prevent it from turn- 

 ing round, in the operation immediately following. This consists 

 in the application, under the influence of great pressure, of from 

 three to six strips of copper, or other metal, which may best resist 

 the action of sea-water. The strips are coiled upon reels, and arc 

 accurately guided into the revolving covering tool, so as to overlap 

 each other equally for nearly half their breadth ; the pressure 

 applied being sufficient to crush, or socket, the one metal down 

 where it is covered by the other. The cable thus formed passes 



