Dec. 7, 1883.] 



♦ KNOWLEDGE ♦ 



345 



SUBMARINE CABLES. 



THE facts that the sum of £12,54.5,000 has been in- 

 vested in the one French and seven English cables 

 providing telegraphic communication between Europe and 

 North America, that the majority of this investment came 

 from the British public, and that the present market value 

 is only (approximately) X7, 000,000, give evidence, were 

 evidence wanting, of the interest that is felt by the specu- 

 lating and moneyed public in oceanic telegraphy. Apart, 

 however, from a shareholder's point of view, the interest 

 evinced by the "general" public from the time that the 

 first Transatlantic Cable was laid, and for his share in 

 which operation Mr. C. Bright received the honour of 

 knighthood, down to the present moment, is a keen one. 

 Nor is this interest confined to the cables above-mentioned. 

 Events of the past few years have progressed at so rapid a 

 rate, changes in political geography have been so extensively 

 and unexpectedly made, that the saying that "upon the feeble 

 strands of copper connecting the various quarters of the 

 globe depends the fate of empires," is not altogether with- 

 out a warrant. It would be an interesting calculation to 

 sum up the grand total of the telegraph systems throughout 

 the world, more ('specially as only a few days since the 

 fiftieth anniversary of the erection of the first telegraph 

 line was celebrated in Germany. Equally interesting, too, 

 would be a study of the improvements that have been 

 made year by year, and almost month by month, 

 in the development of the various systems in vogue. 

 In the case of submarine telegraphy, much has 

 been learned, but most probably much more remains 

 to be learned. The average life of a cable is very short, 

 and is affected by a multitude of causes. The connection 

 between the electrician, the geographer, the physicist, and 

 the naturalist in cable-laying and repairing is so close that 

 anything bearing on the subject is sure to receive ready 

 and careful attention. It is therefore not impossible that 

 the meeting of the Society of Telegraph Engineers, held 

 on the 29th ult., will form one of the landmarks in the 

 history of industrial science. A lengthy discussion lesulted 

 from a short paper, contributed by Captain S. Trott and 

 Mr. F. A. Hamilton, in which the authors took up a most 

 daring amd startling standjwint In effect they en- 

 deavoured to demonstrate that in one of the most im- 

 portant details of cable manufacture we were utterly 

 at fault, that not only were we failing to do that 

 which is right, but that we were absolutely doing 

 our best to insure the inefSciency of the cable. This 

 opinion from one wlio has probably had more practical 

 experience in repairing deep sea cables than any other 

 living man, demands the most serious consideration. It 

 is no wonder then that several gentlemen, many of whom 

 could record considerable experience in cable laying, were 

 placed upon their mettle, and entered into the discussion 

 with the greatest interest. 



As our readers are probably aware, the general method 

 adopted in the manufacture of a cable is to enclose the 

 copper conductor in one or more coatings of gutta-percha, 

 or other insulating material, to surround this with a layer 

 of tarred hemp, and to envelop the whole in a heavy iron 

 armour composed of stranded stout iron wire. 



The principal accidonta to wliich theso cables are liable may be 

 briefly ciiumoratod (say the authors) as follows : — Abrasion by 

 ice and on rocky and stony bottom ; ruptures caused by vessels' 

 anchors; injuries inflicted by marine insects; and the wrinr/imj 

 asunder of the core hij the iron wires. 



Accidents arising,' from the first cause have not been numerous ; 

 indeed, taking into consideration the heavy masses of ice that 

 beset the coasts and banks of Newfoundland and Cape Breton 

 Island, and extend far west along the shores of Nova Scotia, it is 

 marvellous that so few cases of crushing have occnn-ed. 



With regard to breaks on rocky and stony bottom, it is worthy 

 of remark that, excepting in the case of those which have taken 

 place in the immediate vicinity of the shore or in very shallow 

 water, few can be recorded ; and we may here state, as the result 

 of long and careful observation, that cables are rarely chafed 

 tlirough, and we believe that injuries attributed to this agency 

 should in some instances be put down to quite another cause. 



The number of breaks which have occurred to some cables, in 

 consequence of fishing-vessels hooking them with their anchors, is 

 greatly in excess of those brought about by any other means ; but 

 as these accidents are to a great extent unavoidable, and are easily 

 and rapidly repaired, we will dismiss this portion of our subject 

 with the remark, that considering the number of vessels engaged in 

 the great fisheries on the banks lying between the meridian of 48^ 

 and 70° West, the wonder is that the cables are not broken far more 

 frequently. 



In reference to faults caused by marine insects, it can be said 

 that, although the Atlantic cables have not enjoyed a complete 

 immunity, they have been remarkably free from any very serious 

 attacks of these borers, and, as their assaults can be repelled by 

 well-known means, we do not consider the question a very promi- 

 nent one, as far as Atlantic cables are concerned. 



It is, however, on " the wringing asunder of the core by 

 the iron wires " that the authors have chiefly to speak. 

 Records are very numerous showing that cables have 

 " suddenly snapped without any perceptible cause," and, 

 " with everything favourable, have parted silently and sud- 

 denly;" breaks which, according to Dr. Russell, " seemed to 

 point to some mysterious agency e.xisting in the depths of 

 the ocean, beyond the perception of science or man's cen- 

 tral." " The agency described as mysterious still exists," 

 say the authors, " and the history of some of the most 

 recent Atlantic cables, if published, would prove that these 

 so-called improved types are liable to the same mishaps as 

 those we have mentioned ; indeed, they are even more 

 liable, for, notwithstanding their strength, it is quite as 

 difficult, and even more so, to recover them from deep 

 water." The question is asked, " Why do cables suddenly 

 sever in deep water whilst being submerged, or when being 

 picked up, and even after being successfully submerged 1 ' 

 The answer is, that 



Iron-armonred cables have a strong tendency to twist or curl, as 

 the spiral lay of the wires imparts a constant helical force in a 

 direction contrary to the lay. 



Consequently, any slack given is apt to result in a kink or a 

 succession of kinks, which is followed by a wringing asunder of the 

 fabric when the strain is renewed. This accounts for most of the 

 misfortunes which have happened in submerging some cables, for 

 whenever it became necessary to stop or slacken speed in shifting 

 from one tank to another, or for some other purpose, the risk of 

 this accident has always been incurred. 



An iron-armoured cable cannot be recovered from deep water 

 excepting in short lengths, because the operation of heaving-in 

 causes the armour to unlay or untwist, and this results in an accu- 

 mulation of turns at and near the ocean bed, and a wringing or 

 wrenching asunder of the fabric is sure to occur. 



Cables sometimes break in deep water, because when the iron 

 wires become weakened by corrosion, the curling or untwisting 

 tendency is unopposed, and the stronger portions on either side 

 of the weakened spot untwist, thus exerting a force contrary in 

 direction on each side, but concentrated in action at the damaged 

 portion. 



This is the whole secret— this is the mysterious agency, and thus 

 it is that the most serious cause of injury to submarine cables 

 must be attributed to the iron wires. 



Further on the authors maintain that gutta-percha is 

 practically indestructible, but iron wire has caused the 

 loss of many miles of submarine cables, and that, except- 

 ing when in contact with iron, vegetable fibre is inde- 

 structible. 



We could (the authors dcclai-e) cite numerous instances of 

 cables having been lifted from considerable depths solely by means 

 of the yum portion of the fabric, which retains its strength suffi- 

 ciently to bear the superincumbent weight of oxidised iron wires. 

 The core serving, which is composed of common jute yarn, has 

 time after time done duty as the strength-giving material, although 



