42 THE POPULAR SCIENCE MONTHLY. 



Fleeming Jenkin has seen a fault 18 inches long due to this cause, 

 and it is asserted that the same cause destroyed the Toulon-Algiers 

 cable, which was connected to the land-lines without lightning-guards. 



We are every now and then startled by the announcement that 

 light cables are to be preferred to the present iron-clad type, and the 

 object of this investigation has been to discover what data there are 

 to justify any pi'eference to one form of cable over another. I have 

 said already that the committee called attention to the remarkable fact 

 that, in almost all cases, small cables have been found liable to mis- 

 haps, while the heavier the cable the greater had been its durability. 



Mr. Newall, in his evidence, said that the hemp-covered cable 

 which he attempted to lay in 1859, between Candia and Egypt, had 

 the hemp eaten off by the teredo in a very short time, and it was too 

 weak to recover for repairing. The same firm laid an unprotected core 

 from Varna to the Crimea, and it lasted until the winter set in ; it is 

 frequently said that it was cut by order of the French commander-in- 

 chief, but there is no proof of this, and I am not disposed to believe 

 it. Mr. Woodehouse, the engineer who laid this core, said in his 

 evidence he " should not advise anybody to lay so light a cable across 

 the Atlantic, because so small a strain would break it. Ifitisonce 

 safe at the bottom, perhaps it may rest." Mr. Newall said he thought 

 it folly to lay any thing excepting unprotected core. Consistently 

 with this conviction, he laid in 1869 several lines of unprotected India- 

 rubber core, connecting the Grecian islands with the main-land ; they 

 were protected only near the shore. The sea is quiet and tideless in 

 those parts; no better spot could be wished for the experiment, yet 

 they every one of them gave out within two years. 



The Red Sea cable, covered externally with light wires, and unpro- 

 tected with bituminous compound, was so rusted in a short time that 

 it could not be lifted for repairs. 



Notwithstanding, Mr. Newall's partiality for light cables, he sug- 

 gests at the close of his evidence what I assume he would consider 

 the most perfect form of cable. He would cover the copper with 

 India-rubber, protect this core with steel wires vulcanized, the whole 

 then passed through heat; thus insulating all the wires, he would make 

 the cable in one length, and have no joints. Mr. Fleeming Jenkin, in 

 his report to the International Exhibition of 1862, says : 



" So long as the iron wires lasted, the cables frequently continued to work 

 in spite of faults, but sooner or later the iron wires of all these light cables 

 rusted away in parts ; so soon as this took place they one and all broke up into 

 short sections ; this fact has been observed in depths of 100 fathoms ; " the reasons 

 were not obvious to Mr. Jenkin, but he says : " Meanwhile the use of large iron 

 wire seems a sure guarantee against this danger, for as yet no cable covered 

 with wire of the large gauges has ever parted in the manner described. The 

 difficulty is, to find a permanent material which shall retain its strength and con- 

 tinue to afford protection after the cable is laid." 



