When hemp has been split into very fine fibres by the hatchel, it become ex ceedingly soft and pliant, and after it has lain for some time in the form of fine yarn, it may be unreeled and thrown loose, without losing much of its twist. Two such yarns may be put on the whirl of a spinning wheel, and thrown like flaxen yarn, so as to make sewing thread. It is in this way, indeed, that the sail makers' sewing thread is manufactured, and when it has been kept on the reel, or on balls or bobbins for some time, it retains its twist as well as its uses require. But this is by no means the case with yarns spun for great cordage. The hemp is so elastic, the number of fibres twisted together is so great, and the diameter of the yarn (which is a sort of lever, on which the elasticity of the fibre exerts itself,) is so considerable, that no keep ing will make the fibres retain this con strained position.
The end of a rope-yarn being thrown loose, it will immediately untwist, and this with considerable force and speed. It would, therefore, be a fruitless attempt to twist two such yarns together ; yet the of man has contrived to make use of this very tendency to untwist not only to counteract itself, hut even to pro duce another and a permanent twist, which requires force to undo it, and which will recover itself when this force is removed. Every person must recol lect, that when he hail twisted a pack thread very hard with his fingers between his two hands, if he slackens the thread by bringing his hands nearer together, the packthread will immediately curl up, running into loops or kinks, and will even twist itself into a neat and firm cord. The component parts of a rope are called strands, and the operation of uniting them with a permanent twist is called laying or closing, the latter term being chiefly appropriated to cables and other very large cordage.
The process for laying or closing large cordage is this : the strands of which the rope is composed consist of many yarns, and require a considerable degree of har dening. This cannot be done by a whirl driven by a wheel-band ; it requires the power of a crank turned by the hand. The strands, when properly hardened, become very stiff, and when bent round the top, are not able to transmit force enough for laying the heavy and unpliant rope which forms beyond it. The elastic twist of the hardened strands must, there. fore, be assisted by an external force. All this requires a different machinery and a different process. At the upper end of the walk is fixed up the tackle-board, this consists of a strong oaken plank, called a breast board, having three or snore holes in it, fitted with brass or iron plates. Into these are put iron cranks, called heavers, which have hooks or fore locks, and keys, on the ends of their spin dles. They are placed at such a distance from each other, that the workmen do not interfere with each other while turn ing them round. This breast board is fixed to the top of strong posts, well se cured by struts, or braces, facing the lower end of the walk. At the lower end is another breast board, fixed to the up right post of a sledge, which may be loaded with stones or other weights. Si milar cranks are placed in the holes of this breast board; the whole goes by the name of the sledge. The top necessary for closing large cordage is too heavy to be held in the hand ; it therefore has a long staff, which has a truck on the end : this rests on the ground, but even this is not enough in laying great cables. The top must be supported on a carriage, where it must lie very steady, and it needs at tendance, because the master workman has sufficient employment in attending to the manner in which the strands close behind the top, and in helping them by various methods. The top is therefore fixed to the carriage, by lashing its staff to the two uprights posts. A piece of soft rope, or strap, is attached to the han dle of the top by the middle, and its two ends are brought back and wrapped se veral limes tight round the rope, in the direction of its twist, and bound down.
This greatly assists the laying of the rope by its friction, which both keeps the top from flying too far from the point of union of the strands, and brings the strands more regularly into their places. The first operation is warping the yarns. At each end of the walk are frames called warping frames, which carry a great num ber of reels or winches, filled with rope yarn. The foreman of the walk takes off a yarn end from each, till he has made up the number necessary for his rope or strand, and bringing the ends together, he passes the whole through an iron ring fixed to the top of a stake driven into the ground, and draws them through : then a knot is tied on the end of the bundle, and a workman pulls it through this ring, till the intended length is drawn off the reels. The end is made fast at the bot tom of the walk, or at the sledge, and the foreman comes back along the skein of yarns, to see that none are hanging slacker than the rest. lie takes up in his hand such as are slack, and draws them tight, keeping them so till lie reaches the upper end, where he cuts the yarns to a length, again adjusts their tightness, and joins them altogether in a knot, to which he fixes the hook of a tackle, the other block of which is fixed to a firm post, called the warping post. The skein is well stretched by this tackle, and then separated into its different strands. Each of' these is knotted apart at both ends. The knots at their upper ends are made fast to the hooks of the cranks in the tackle-board, and those at the lower ends are fastened to the cranks in the sledge. The sledge itself is kept in its place by a tackle, by which the strands are again stretched in their places, and every thing adjusted, so that the sledge stands square on the walk, and then a proper weight is laid on it. The tackle is now east offi and the cranks are turn ed at both ends, in the contrary direction to the twist of the yarns (in some kinds of cordage the cranks are turned the same way with the spinning twist.) By this the strands are twisted and hardened up, and as they contract by this opera tion, the sledge is dragged up the walk. When the foreman thinks the strands sufficiently hardened, which he estimates by the motion of the. sledge, he orders the heavers at the cranks to stop. The middle strand at the sledge is taken off from the crank ; this crank is taken out, and a stronger one put in its place. The Other strands are taken off from their cranks, and are all joined on the hook which is now in the middle hole the top is then placed between the strands, and being pressed home to the point of their union, the carriage is placed under it, and it is firmly fixed down : some weight is taken off the sledge. The heavers now begin to turn at both ends ; those at the tackle board continue to turn as they did be fore, but the heavers at the sledge turn in the opposite direction to their former motion, so that the cranks at both ends are now turning one way. By the mo tion of the sledge-crank the top is forced away from the knot, and the rope begins to close. The heaving at the upper end restores to the strands the twist which they arc constantly losing by the laying of the rope. The workmen judge of this by making a chalk mark on intermediate points of the strands, where they lie on the stakes which are set up along the walk for their support. If the twist of the strands is diminished by the motion of closing., they will lengthen, and the chalk mark will move away from the tackle-board ; but if the twist increases by turning the cranks at the tackle board, the strands will shorten, and the mark will come nearer to it. As the closing of the rope advances, the whole shortens, and the sledge is dragged up the walk. The top moves faster, and at last reaches the upper end of the walk, the rope being now laid.