In preparing the hemp for spinning an ordinary thread of rope yarn, it is only heckled over a large keg or clearer, until the fibres are straighted and sepa rated so as to run freely in the spinning. In this case the hemp is not freed of the tow or cropt, unless it is designed to spill beneath the usual grist, which is about twenty yarns for the strand of a three inch strap laid rope. The spinning is still performed by hand, being found not only more economical, but also to make a firmer and smoother thread than has yet been effected by machinery. Various ways have been tried of preparing the yarns for tarring. That which seems now to be most generally in use, is to warp the yarns upon the stretch as they are spun. This is accom plished by having a wheel at the foot as well as the head of the walk, so that the men are able to spin both up and down, and also to splice their threads at both ends. By this means they are formed into a haul re sembling the warp of a common web, and a little turn is hove into the haul to preserve it from getting foul in the tarring. The advantages of warping from the spinners as above, instead of winding on wenches, as formerly, are, I st, the saving of this last operation alto gether; 2dly, the complete check which the foreman has of the quantity of yarn spun in the day; and 3dly, that the quality of the work can be subjected to the minutest inspection at any time. In tarring the yarn, it is found favourable to the fairness of the strip, to allow it to pass around or under a reel or roller in the bottom of the kettle while boiling, instead of coiling the yarn in by hand. The tar is then so pressed from the yarn by means of a sliding nipper, with a lever over the upper part, and to the end of which the necessary weight is suspended. The usual proportion of tar in ordinary ropes is something less than a fifth. In large strap-laid ropes, which are necessarily subjected to a greater press in the laying of them, the quantity of tar can scarcely exceed a sixth, without injuring the ap pearance of the rope when laid.
For a long period the manner of laying the yarns into ropes, was by stretching the haul on the rope ground, parting the number of yarns required for each strand, and twisting the strands at both ends by means of hand-hooks or cranks. It will be obvious that this method, especially in ropes of any consider able size, is attended with serious disadvantages. The strand must ever be very uneven; but the principal disadvantage, and that which gave rise to the many attempts at improvement, was, that the yarns being all the same length before being twisted, it followed when the rope was finished, that while those which occupied the circumference of the strand, were perfectly tight, the centre yarns on the other hand, as they were now greatly slackened by the operation of hardening or twisting the strands, actually would bear little or no part of the strain when the rope was stretched, until the former gave way. The method displayed in the accompanying drawing and description is among the latest and most approved. Every yarn is given out
from the bobbin frame as it is required in twisting the rope; and the twist communicated in the outgoing of the carriage, can he increased or diminished at plea sure. In order to obtain a smooth and well-filled strand, it is necessary, also, in passing the yarns through the nipper board, to proportion the number of centre and outside yarns. We know of no arithmetical proportion for ropes of all sizes; but in ordinary sized ropes, the strand seems to have the fairest appearance when the outside yarns form from 2-3ds to 3-4ths of the whole quantity in the strand. But the nicest part of the oper ation is the proportion of twist given by the carriage in drawing out and forming the strands. Were the whole twist necessary, communicated then, and the rope closed without the operation of hardening, the whole strain would bear on the centre yarns when the rope came to be stretched. The object of hardening (that is twisting the strands at both ends before putting in the top to close the rope,) seems to be, at once to tighten and firm the strand, and also so to ease the centre yarns, as that too much strain may not fall upon them either in closing or afterwards in stretching the rope. We find the twist to he in this proportion when one complete turn of an outside yarn occupies as much space along the strand as the circumference of the rope itself when made. This is easily seen by attach ing a white thread to an outside yarn before it reaches the nipper. It may be also ascertained by the differ ence of length between the centre and an outside yarn, taken in connexion with the circumference of the rope; but the former method is the simplest and most satis factory. It may be remarked also, that this refers to strap-laid ropes only. In hawser, or cant-laid ropes, as they are called, the proportion twist is fully 8th less. Where this is not attended to, the hawser, or cable, will be found to be stiff and unmanageable. However, it is difficult to give precise arithmetical proportions. The ropemaker should have frequent recourse to experiment, that is, to the examination of the rope after being stretched or used; and as he pre viously knew the proportion of twist in drawing out, and in hardening, to vary those according to the ob servations which he makes. In hardening the strands of a strap-laid rope, the carriage usually comes in fully more than one-tenth of the length of the strand. In laying the strands together, it only requires to be at tended to, that, while as much after turn is given as is necessary for the right formation of the rope, just so much twist should be communicated to the strands by the forehooks, as will counteract the opposite or after turn. This is easily seen by observing whether the strands before the top, are shortening, or otherwise, while the rope is closing. A chalk mark upon the strand, close by a stake-head, will show this. If this is not attended to, and too much turn given, some of the outside yarns will most probably snap, even in the closing.