72 SUBMAKINE CABLE LAYING AND KEPAIEING-. 



in one operation. The first patent for applying a metal tape 

 to a cable was that of C. T. and E. B. Bright in 1852. 

 According to this the tape was laid on outside the inner serving 

 of jute. Mr. Henry Clifford, of the Telegraph Construction and 

 Maintenance Co., afterwards introduced the method above 

 referred to of laying the metal tape next the core, now generally 

 adopted in cables requiring this protection. Cables liable to 

 the depredations of the teredo are, as a rule, only those in 

 shallow waters of 300 or 400 fathoms. This pest does not 

 appear to exist at all at great depths, and the cores of deep- 

 sea cables are quite unprotected in this way. In exceptional 

 cases, however, where currents of higher temperature or 

 submarine hoc springs exist at considerable depths, this 

 protection is adopted as a safeguard against the possibility of 

 these or other cable-attacking insects being present. In the 

 Java and Straits of Malacca cables, which came more im- 

 mediately under the author's observation, these animals were 

 very lively, but the brass-taped cables laid in 1879 effectually 

 kept them at bay. In multiple-core cables for shallow water 

 it is usual to adopt the original method of laying the metal 

 tape over the inner jute serving on account of the saving of 

 material effected in protecting all cores with one serving. 

 There is the additional advantage in this method of protecting 

 the jute, which is said to have an attraction for boring insects. 

 For this purpose, also. Bright and Clark's compound, con- 

 taining mineral pitch, tar and finely powdered silica, is used in 

 alternate layers, with j ute yarn outside the sheathing wires, by 

 most manufacturing companies. From the success of this 

 compound it would seem that the sensation felt by the insect 

 as its boring fang touches the sharp glass-like grains is one 

 which it does not care to experience again. 



With regard to the mechanical protection of the core, there 

 is first what is termed the inner serving — namely, a serving of 

 jute yarn laid over the core as a buffer or cushion between it and 

 the heavy iron wires forming the outside armouring. The jute 

 J am, treated by steeping in cutch or brine before laying on, is a 

 very strong material, and it is now manufactured of a quality 

 more durable than hemp. In the early days hemp was largely 

 used for this serving, but the improvements made in the quality 

 of jute yarn, coupled with its lower price, render it infinitely 



