Both the machines here described are made in a great variety of sizes, and with different numbers of hooks, according to special requirement. Their capacity is very wide, as they will make ropes from the smallest aizea up to 24 in. in circumference. In order to be of the greatest use, they require a full complement of change-wheels and strand-tubes. Sometimea a foreturn will havo two travellers, olio light and one heavy. When one is in use, the other is run into a siding, or on to an extension of tho line ln yond the requirement of that in use.
The aelcotion of the factory or walk system of manufacture will generally bo decided by the special circuinstaneea of the case, aa each has its advantagee and dieadvantagea. The factory or " house" machines, as they are called, are said to be capable of turning off more rope of a better quality, and at losa coat for wages and driving-power, than the " walk " machines, though this is a disputed point. They need much lese space for their operations, nO " walk " and long shed being required. But the machines are numerous and expensive, where a full equipment is necessary, the first outlay and cost of maintenance being greater than when the foreturn and traveller are the chief machines employed. The latter are the simplest, and, where land and labour are cheap, may in some cases he the most advantageous.
The greateat proportion of ropes manufactured are made from tarred yarna. There are two methods of tarring in use : in one, the yarns are tarred singly ; in the other, by the " haul." Yarna are tarred singly by arranging a number of large bobbins, usually about 16, on which the untarred yarns are wound, in a creel it, front of a double-cased copper steam-vat, in which the tar is kept boiling by moans of steam circulating in the cavity. In the pan, a copper or brass roller is adjusted, partly immersed in the tar. Over this roller, the yarns aro conducted, and as they pnes in contact with it, receive some of the boiling tar, which it hrings up in its revolution. The yarna are next drawn along a copper trough, in which are placed hide ropes twisted tightly round them, whose function it is to equally distribute the tar, and, by friction, to lay the fibres, and polish the yarn. Leaving the trough, they are wound upon a large 'eel, and formed into a haul. In tarring in the haul, the yarna aro wound upon a large reel, or warping-mill, in a helical form by a traversing motion, before being subjected to the tar. When the first layer is complete, the threads are passed round a pin or peg, and the motion of the reel is reversed until a second layer ia completed. These operations are continued until a warp containing 200-400 threads is made, which is then wound off, and coiled on a revolving plate or iron dish upon a bogie, which ie made to revolve for the purpose of imparting to the warp a fow turns of twist, to prevent the entanglement of the threads in passing through the subsequent processes and during mellowing. Tho warp is then taken to the tarring
machine, Fig. 1202, conaisting of a large trough or cistern, in which the tar is kept at boiling heat by means of coils of copper steam-piping. The yarn or warp is conducted through the boiling tar, and the pressing-apparatus, being drawn through by means of the gearing actuating the sheaves, around which it is twioe passed to prevent slipping, and is then coiled for the store. The difference in these processes is not very material : in the first case, the yarns are tarred before they are made into a warp; in tlao second, after that operation. In tarring singly, the yarns are warped aa they emerge from the tar-pan.
When the tarring procesa has been completed, the " hauls" or tarred warps arc conveyed into the store, in order to he mellowed, which is eimply allowing the tar to penetrate the fibres. The time for this varies acoording to the quality of the work for which they are intended. Two months is stated to be the shortest time in which this can be accomplished ; it is done much better when 6-8 months are devoted to it. In the Royal dockyards, it is customary to allow 12-15 months for the process. The tar used should be clear and of a light colour, in order to impart the best appearance. Contact with iron, when it is fluid, darkens and discolours it, and this should therefore be carefully avoided.
When the tarred yarns are required for use, they are brought from the mellowing-store ; the warps are wound upon the reel ; the threads are separated, and wound upon bobbins from the reel, thus reversing the previous operations; and the bobbins are conveyed to the stranding-machines to pass through the processes previously described.
Exports.—Our exports of cordage, cables, and ropes of hemp and similar material in 1880 were to :—Australia, 16,665 cwt., 54,155/. ; British N. America, 16,264 cwt., 34,766/. ; British W. Indies and British Guiana, 8886 cwt., 18,662/. ; Brazil, 8409 cwt., 23,237/. ; British S. Africa, 7074 cwt., 17,767/. ; Argentine Republic, 6378 cwt., 11,487/. ; Germany,5130 cwt., 12,823/. ; France,4027 cwt., 8942/. ; Sweden and Norway, 3615 cwt., 10,272/. ; Bombay and Sind, 3589 cwt., 8963/. ; Chili, 3356 cwt., 7564/. ; Peru, 2767 cwt., 5355/. ; Italy, 2531 cwt., 5696/. ; Japan, 2399 cwt., 4944/. ; United States, 2018 cwt., 4169/. ; Bengal and Burma, 1927 cwt., 7642/. ; British W. Africa, 1270 cwt., 4214/. ; Channel Islands, 1048 cwt., 6000/. ; other countries, 20,964 cwt., 48,949/. ; total, 118,307 cwt., 295,607/. R. M.
(See Fibrous Substances.)