Mr. Chapman gives the following notice of the mode of classifying the work in her majesty's dockyards. Petersburg hemp is mostly used for cables and cablets; Dalian hemp for bolt rope and breechings; and Riga hemp for all other cordage. To mako l'etersburg hemp into No. 20's, the hemp is given to the hatcheller in bundles of 70 lbs.; he takes out 7 lbs. of aborts, and gives 63 lbs. of heckled hemp to the spinner, who spins it into 18 threads of 170 fathoms and 34 lbs. each. To make Riga hemp Into No. 25's, the hemp is given to the hatcheller in bundles of 56 lbs.; he takes out 5 lbs. of shorts, and gives 51 lbs. of heckled hemp to the spinner, who spina 18 threads of 170 fathoms and lbs. each. In using Italian hemp, 16 lbs. of shorts are taken out of 112 lbs. of hemp; and the remaining 06 lbs. are made op into bands of If to 34 lbs. each, according to the size of the yarns to be made. Much old-fashioned routine still prevails in the royal dock yards, In defining exactly how many porters, garters, hatchellers, wheel turners, spinners, &c., shall be employed for each ton of hemp.
have hitherto spoken only of hemp as the material employed; hut several other kinds of vegetable fibre have been made use of in the manufacture of cordage; and some appear greatly to exceed hemp in strength. In a comparative trial made at Paris between ropes made of hemp and of the aloe from Algiers, the latter was found to bear 2000 kilogrammes, while the former, of equal aizo, bore only .100. Ropes have been formed also of long wool ; but they aro only about one-third as strong as the best hempen cordage of the same size. Ropes composed of fibres of hemp intermixed with threads of caout choue are very valuable for some purposes, owing to their superior strength and elasticity. Their power of bearing sudden jerks without injury is a highly important property. Such a rope was used with the grapnel or anchor of the great Nassau balloon, and was found to arrest the balloon without any unpleasant check when the grapnel caught. Ropes made of thongs of ox-hide twisted together are used in the rope-bridges of Peru, and for some other purposes. Coir or cocoa-nut fibre has lately been much used for this purpose, owing to the high price of Russian hemp ; it wears well, weighs little, and is cheap; and is useful for hawsers and warps owing to its great elasticity.
Wire Ropes.—Iron is the substitute which is now engaging most attention. Ropes formed of this metal are found to effect a great saving of expense from their durability and superior lightness. From a paper communicated by Count Breunner to the British Association in 1838, it appears that such ropes had been introduced about seven years before, in the silver mines of the Harz Mountains, and had been found so advantageous as almost entirely to supersede flat and round ropes of hemp in the mines of Hungary, and most of those in the Austrian dominions. The count observes that these iron ropes are nearly equal in strength to solid bars of the same diameter, and equal to hempen ropes of four times their weight. One of them had been in use for upwards of two years without any perceptible wear, though a common flat rope performing the same work would not have lasted much more than one year. The diameter of the largest rope in ordinary use is one inch and a half, and it is composed of three strands, each con taining five wires. Great care is observed in the manufacture of these ropes, that the ends of the wires may be set deep in the interior of the rope, and that two ends may not occur near the same part. In use, it is necessary that the ropes be wound on a cylinder of not less than eight feet diameter, and be kept well coated with tar, to prevent oxidation. In one case mentioned by Count Breunner, so great a saving of power was effected, that four horses were doing as much work with a wire rope as six with a flat hempen rope.
Prior to the date of this memoir, patents had been obtained in this country for the manufacture of wino ropes ; and they have since been improved and acted upon. The wire ropes of Mr. Andrew Smith are formed in various ways, according to their intended use. For stand
ing rigging straight untwisted wires are employed, bound round with cloth or small hempen cordage saturated with a solution of caoutchouc, asphaltum, or other preservative from rust. Flat ropes may likewise be made of straight wires, interwoven or wrapped with hempen yarn, or sewed between canvas, fic.; but the patentee prefers using them with a slight twist. Other ropes are formed much in tho same way as those of hemp; the wires taking the place of rope-yarns, and being twisted into strands, and combined into ropes, both hawser-laid and cable-laid. The twisting should not be so hard as in hempen cordage; and all the wires must be protected by an anticorrosive composition, or by coating with tin, zinc, fic. Ina patent obtained by Mr. Newell of Dundee, for improvements in wire ropes, coating with the follow ing mixture is recommended :—Tar, six parts; linseed oil, two parts ; and tallow, one part : the whole being melted together, and applied while hot. In this patent it is proposed to twist wires round a core, either of wire, hemp cord, spun yarn, or other material, to form a strand ; and to lay such strands round a similar core when there are more than three strands iu a rope. For joining the wires, Messrs. Smith and Newall both recommend twisting their ends together for a few inches; and the latter also suggests the possibility in some cases , of welding them. Wire ropes may be very conveniently and firmly secured at their ends by passing them through the small end of a conical collar, and doubling up, or upsetting, the ends of the wires, which may then be welded into a solid mass, or secured by running melted braes or solder among them. The collars may then be attached, in various ways, to anything with which it is desired to connect the rope ; or they may, as suggested in Newell's patent, be screwed together, so as to unite several lengths of rope. Iron is the material usually employed for wire ropes, but copper and other metals may also be used. The annexed table, showing the comparative size and weight per fathom for equal strength, gives the result of experiments with the wire ropes of Mr. Andrew Smith, and may serve to show their great superiority to those of hemp, which they surpass even in flexibility :— Experiments were made at Liverpool in 1857, to find the relative strength of hempen rope and wire rope for the standing rigging of ship.; as determined by the corporation testing-machine at King's All the ropes were made by Messrs. Garnock and Bibby, with equal care. The followingjasultis were obtained :— The advantage of iron is here very obvious ; indeed this metal is foul to be, for a given strength, less heavy, less bulky, one-fourth cheaper, and less affected by the atmosphere, than hemp. Soft wire makes the most pliable rope for splicing ; but hard wire is stronger. Three-fourths of all the ships now rigged at Liverpool are provided with iron wire standing rigging.
Some of the machines for making wire rope act in the following way. The wire is wound in bobbins mounted in frames set on the periphery of a larger frame like a cage. The cage revolves round an ails, on the bottoru of which is a fixed spur-wheel ; and the lower end of the vertical axis of each bobbin-frame carries a spur-wheel gearing into this. There is thus obtained a sort of sun-and-planet' motion, the cage carrying the bobbin round the central axis, and each bobbin frame revolving also on its own axis. The wires, in their progress from the bobbins, pass through holes in the top of the central axis, and are there united to form the strand or rope. In Mr. Newell's patent of 1857, the Strand-wire for electric cables is drawn through dies or between rollers after the twisting, to bring it to a close cylindrical form, and thereby aid the electric conduction.
The demand for wire rope being now very extensive, for shipping and for telegraphic cables, the patents are or have been regarded as valuable property. Mr. Newell's first patent, which expired in 1854, was a subject of many legal contests, arising out of infringements.