CABLE 559 



gothor, the slenderer parts are at the sides, and the thicker at the ends of the elliptic 

 links. Such rods as the above are formed at once by rolling, swaging, or any other 

 means ; but in practice, this plan has not been extensively carried out ; the simple 

 round iron seems best. 



The first avowed proposal to substitute iron cables for cordage in the sea service is 

 stated to have been made by Mr. Slater, surgeon of the Navy, who obtained a patent for 

 the plan in 1808, thoughhe does not seem to have had the means of carrying it into effect 

 a very general misfortune with ingenious projectors. It was Lieut. Samuel Brown, 

 of the Koyal Navy, who, in January 1808, had represented to the Naval Boards the 

 policy of employing iron rigging and chain cable, and who, in February of that year, 

 enrolled a patent for those articles, and in 1811 first employed chain cables in the 

 vessel ' Penelope,' of which he was commander, for the purpose of experimental ex- 

 perience, this vessel of 400 tons having been fitted expressly for the trial by Captain 

 Brown, Mr. Bruton, and other friends, at personal expense and risk, with iron rigging, 

 chains, and cables, in place of hemp and rope. 



He made a voyage in this ship from England to Martinique and Guadaloupe and 

 home again, in the course of four months, having anchored many times in every 

 variety of ground without any accident. He multiplied his trials, and acquired 

 certain proofs that iron might be substituted for hemp in making cables, not only for 

 mooring vessels, but for the standing rigging. Upon his return from the West Indies, 

 Captain Brown strongly represented the advantages practically experienced of iron over 

 hemp. A committee of naval officers reported upon the whole affair, and the Govern- 

 ment ordered the ' Namur ' of 74 guns, the ' Monmouth ' of 64, the ' Crescent ' frigate, 

 and the ' Alonzo ' sloop, to be fitted \vith two chain cables of 100. fathoms each, and 

 Lieut. Brown was promoted to the rank of captain. These chains -were of various 

 forms of links ; those, for instance, supplied to the ' Crescent ' were composed of very 

 short links with parallel sides. 



Since this period, chain cables have been universally introduced into all the ships of 

 the Koyal Navy ; but the twisted links employed at first by Brown have been replaced 

 by straight ones, stayed in the middle with a cross rod, the contrivance of Captain 

 Brown, which was secured by patent in this country. 



The twisting of the links was done in order to assimilate the chain to the form of 

 rope, and for the purpose of making it run out with less concussion to the ship ; but 

 this in practice was found really to let the cable render out too easily, and -was dis- 

 continued in practice. 



Some of the cables supplied in 1811 to the ships of, war were found to have defec- 

 tive links ; their general use was suspended until the beginning of 1812, when Captain 

 Brown invented a mode of shutting the link with a long scarf, and introduced a 

 machine to put upon the chain any amount of strain that ought to be brought to bear, 

 and thus ascertain defects of workmanship and material. This proving machine led 

 to the introduction of stay pins in the links ; about the middle of 1812, chain cables 

 were thus brought to great perfection, and very generally introduced into the Koyal 

 Navy. 



The first thing to be considered in the manufacture of iron cable is, to procure a 

 material of the best quality, and, in using it, always to keep in view the direction of 

 the strain, in order to oppose the maximum strength of the iron to it. The best form 

 of the links may be deduced from the following investigation : 



Let A B {fig. 307) be a circular link or ring, of one-inch rod iron, the outer cir- 

 cumference of the ring being 15 inches and the inner 9. If equal 

 opposite forces be applied to the two points of the link c i>, pull- 

 ing c towards B, and D towards F, the result will be, when the 

 forces are sufficiently intense, that the circular form of the link 

 will be changed into another form with two round ends and two 

 parallel sides, as seen in fig. 308. The ratio of the exterior to 

 the interior periphery, which was originally as 15 to 9, or 5 to 3, 

 is no longer the same in fig. 308. Hence there will be a derange- 

 ment in the relative position of the component particles, and 

 consequently their cohesion will be progressively impaired, and 

 " 



eventually destroyed. "La fig, 307, the segment M N of the outside ( (r)" 



periphery being equal to 3 inches, the corresponding inside seg- V_ 



ment will be fths of it. If this portion of the link, in conse- Y fi\ z 



quence of the stretching force, comes to be extended into a straight 



fine, as shown in fig. 308, the corresponding segments, interior and exterior, must both 



he reduced to an equal length. The matter contained in the 3 inches of the outside 



periphery must therefore be compressed, that is, condensed into l^inch ; or the inside 



periphery, which is only 1| inch already, must be extended to 3 inches : that is to 



say, the exterior condensation and the interior expansion must take place iu the 



