Discoveries and inventions of the nineteenth century / by Robert Routledge.

  • Routledge, Robert.
Date:
1905
Catalogue details

Licence: In copyright

Credit: Discoveries and inventions of the nineteenth century / by Robert Routledge. Source: Wellcome Collection.

    632/882 (page 576)
    was manufactured, in which the gutta-percha core was protected by a cover- ing of iron wires laid specially on the exterior, and thus combining greater security with a far larger amount of tenacity. A view and section of this —the first practically successful submarine cable—are given in Fig. 297 of the real size. It has four separate copper wires, each insulated with a covering of gutta-percha, and the whole was spun with tarred hemp into the form of a rope, and protected with an outer covering of ten of the thickest iron wires wound spirally upon it The cable when complete was 27 miles in length, and each mile weighed 7 tons. This cable was laid in 1851, and from that time it has been in constant use, with the ex- ception of a few interruptions from accidental ruptures. Its success im- mediately led to the construction of other cables connecting England with Ireland, Belgium, Holland, &c. In 1855 the practicability of an Atlantic cable was no longer doubted, and ^350,000 were soon subscribed by the public for the project. A cable was manufactured weighing 10 tons to the mile,and in August, 1857,338 miles of it had been successfully paid out bythe ships when the cable parted. Better paying-out apparatus was now devised —self-releasing brakes were constructed, so that the cable should not be ex- posed to too great a strain ; and in 1858 another cable, requiring a strain of 3 tons to break it, was manufactured, and the laying of it commenced in mid-ocean—the Mcroera and Aga?)iem)ion going in opposite directions, and paying out as they proceeded. Twice the cable was severed, twice the ships met and repaired the injury ; but the third time, when they were 200 miles apart, the cable again broke. But again the attempt was repeated, and this time success crowned the effort; for on the 5th of August the two continents were telegraphically connected. Unfortunately the electric con- tinuity failed after the cable had been a month in use. Seven years elapsed before another endeavour was made ; but the experience gained in the unsuccessful attempt was not lost; and in 1865 another cable had been constructed, and the Great Eastern was em- ployed in laying it. In this the conductor was composed of seven copper wires twisted into one strand, covered with several layers of insulating material, and covered externally with eleven stout iron wires, each of which was itself protected by a covering of hemp and tar. This cable was 2,600 miles long, and contained 25,000 miles of copper wire, 35,000 miles of iron wire, and 400,000 miles of hempen strands, or more than sufficient to go twenty-four times round the world. It was carefully made, mile by mile, formed into lengths of 800 miles, and shipped on board the Great Eastern in enormous iron tanks, which weighed, with their contents, more than 5,800 tons. This cable was manufactured by Messrs. Glass and Elliot, at Greenwich, to whom the iron wire for the outer covering was furnished by Messrs. Webster and Horsfall, of Birmingham. Fig. 298 represents the workshops with the iron wire in process of making. The great ship sailed from Valentia on the 23rd of July, 1865, and the paying out com- jnenced. Constant communication was kept up with the shore, and signals exchanged with the instrument-room at Valentia, which is represented in Fig. 299, where, among various instruments invented by Sir W. Thompson, may be seen his mirror galvanometer. After several mishaps, which re- quired the cable to be raised for repairs after it had been laid in deep water, the Great Easterti had paid out about 1,186 miles of cable, and was 1,062 miles from Valentia, when a loss of insulation in the cable was dis- covered by the electricians on board. This indicated some defect in the portion paid out, and the usual work of raising up again had to be once