TRANSACTIONS OF THE SECTIONS. 187 



been made upon the injector as it first came from the hand of the inventor ; but 

 these cannot be made clear without a reference to diagrams. 



On the Outer Covering of Deep-sea Cables. By C. "W. Siemens, C.E. 



The want of success which has hitherto attended deep-sea cables renders it per- 

 haps desirable that the attention of the Section should be called to the subject. 

 We are able at present to point to shallow sea-lines, such as the Dover and 

 Calais, the Port Patrick and Dunagadee, and the Dover and Ostend lines, which 

 have lasted above fourteen years, and in which the electric conductors, together 

 with their insulating coating, remains to this day unimpaired, although the thick 

 iron wires which constitute their outer covering are greatly diminished in strength 

 through oxidation, and have given rise to occasional repairs. It has, moreover, 

 been proved, beyond doubt, that the great hydrostatic pressure upon deep-sea 

 cables does not deteriorate the insulated conductor, but, on the contrary, greatlv 

 improves the insulation ; and, as regards the durability of the outer covering, deep- 

 sea cables have the natural advantage over shallow* sea-lines that they lie upon 

 tranquil ground far beyond the reach of currents, of accidental disturbances through 

 ship's anchors or the coral-fisher's hooks, and, to some extent at least, beyond the 

 reach of animal life. The drawbacks to these advantages are, that the risk of acci- 

 dent is greater in laying down deep-sea lines, and that, when laid, they are less 

 accessible for repairs ; but these circumstances do not suffice to account for the very 

 rapid failure of those deep-sea cables which had been successfully submerged, as, for 

 instance, the first Atlantic, the Toulon and Algiers, and other lines in the Medi- 

 terranean. 



But why, it may be asked, are deep-sea cables not made precisely the same as 

 shallow sea- or shore-end lines, seeing- that the latter have given proof of greater 

 strength and durability ? The answer is that the laying of a heavy iron-clad cable 

 into deep seas woidd be attended with great risk, because the retarding force which 

 has to be applied to a cable in going overboard increases with the depth (or length 

 of suspended cable), and would amount to several tons ; tug-steamers woidd have 

 to be applied to assist the cable-ship, and any stoppage in the operation through 

 the breakage and entanglement of a wire, or other cause, might seriously compromise 

 the safety of the cable and of the ships themselves. Moreover, deep-sea cables are 

 generally lone/ cables, and ships could hardly be found to carry a heavy cable of the 

 requisite length in one niece, nor could it be joined with safety on the open seas. 

 The risk of breakage of a heavy deep-sea cable woidd also be great, because the 

 thick iron wires composing the same could hardly reach down to the bottom of the 

 North Atlantic without breaking by their own dead weight. 



Considering these circumstances, it becomes evident that the strength and per- 

 manency of a deep-sea cable cannot be attained by thick iron wires, but that other 

 materials and modes of construction must be had recourse to. 



In reviewing past experience, we find that in the case of the Varna and Balaclava 

 cable (300 miles) , which was laid in 1858, no sheathing- of any kind was applied to 

 the insidated conductor. The operation of paving out was accomplished with great 

 ease and success, and the electrical communication was kept open for nearly nine 

 months, when it suddenly ceased, in consequence either of chafing against rocks or 

 shells, or the tooth of the Teredo. 



Several cables were laid in the Mediterranean in 1855 and 1856, consisting of an 

 insidated conductor covered with strings of tarred hemp, which was laid on in the 

 manner of an iron sheathing. A difficulty was experienced in laving this descrip- 

 tion of cable, owing to its excessive specific lightness and roughness of surface, 

 which combined to make it sink so very slowly to the bottom, that it was paid out, 

 as it were, in a straight line upon the surface of the water ; and although no break- 

 power whatever was applied, not sufficient cable would leave the ship to cover the 

 irregularities of the bottom. This tightening of the cable, when laid, was further 

 increased by the shrinkage of the hemp strings in the water, and, moreover, by the 

 action of local currents in the water, to which the cable remained exposed for a long 

 time during its descent. The consequence was that the cable strained and broke 

 during the operation of laying, or rather immediately after. In raising this cable 



