In order to avoid this evil, Mr. Balfour stretched out at length upon a rope ground all the yarns which were to compose the strand, to the same length as the proposed strand. The remaining length of the yarns, or the excess of the length of the yarns above the re quired length of the strand, was to be wound up on as many bobbins as there were yarns placed upon a large frame. The yarns were separated at intervals throughout their whole length from the frame to the commencement, where they all united either through holes arranged in concentric circles, or round the notches of an apparatus, which he called a top minor. The whole of the yarns were then twisted at that end, the top minor retiring as the twist advanced. As the yarns at the opposite end would remove from the bob bins no more than was necessary from their position in the internal or external part of the spiral, they would of course be of different lengths. " This plan," says Mr. Chapman, " was very ingenious, and had much merit in its principle, although defective in stopping short of what would effect the ultimate pur pose of causing all the yarns to bear alike on break ing the rope. Before a rope is brought to its break ing stress, both it and the strands composing it are much elongated, and their diameters greatly reduced. Now, under any reduction of diameter of strand, it is apparent that the outside coat of yarns must slacken considerably, and give no support to the internal yarns, which, from the smallness of the spiral, could elongate but little, and must of course break in suc cession from the centre outwards. In addition to this defective circumstance, the mode of operation was so complex and laborious, as to prevent its adoption. This invention of Mr. Balfour's, though defective and nugatory, has nevertheless been the basis of all future improvements." The defect in Mr. Balfour's method was very ingeni ously supplied by Mr. Joseph Huddart of Islington's "new mode of making great cables, and other cord age, so as to obtain a greater degree of strength therein, by a more equal distribution of strain upon the yarns." This method was secured by patent, in 1793, and was suggested by a practice which Mr. Huddart had seen among the negroes in the West Indies, in making lines of a certain description. Be hind the top minor of Mr. Balfour, Mr. Huddart places a tube, consisting of two parts, divided longi tudinally, and overlapping each other. These tubes, made of thin steel, and brought to a spring temper, may be more or less compressed. Mr. Huddart's top minor consists of a plate, perforated with a proper number of holes for the yarns, arranged in concentric circles; and at a distance from the plate, sufficient to allow the yarns to be easily concentrated, is placed the above-mentioned tube, which is connected with a re gister, which indicates the proper angle of twist dur ing that process, and regulates the increased angle of the next process. The reels which held the yarns, were placed at the head of the rope ground in a sta tionary frame, and as the strand was twisted by the hook of a sledge, the register advanced towards the stationary frame. To the mass of yarn thus formed into a strand, Mr. Huddart gave an additional twist, by which the strand was shortened, and a compensa tion made for the effects of a reduction of its diameter by stretching. Mr. Huddart likewise proposed a method of twisting the yarns while they were forming into a strand, in order to counteract the diminution of strength which would have arisen from the untwisting produced by the countertwist of the strand.
Such was the state of the rope manufacture, when Mr. Chapman of Newcastle took out his first patent for the improvement of cordage, and which was fol lowed by a series of other patents, which appear to have contributed greatly to the present improved state of the rope manufacture. His first patent, dated in 1797, had for its object to dispense with rope grounds, and to reduce the expense of the manufacture. The strands revolved round their own axis only, and the rope was formed by the revolution of a separate axis on which it was wound.
Mr. Chapman's second patent, dated 1798, consisted in tarring the yarns so as to cause them all to wind up singly as they came from the tar kettle; and in making the strand separately by house machinery, and in two distinct methods. The first of these me
thods consisted in having the yarns on separate reels fixed on a platform, supported by the revolving shaft or frame, by which, when the yarns were brought to a focus, the strand was to be twisted, and thence drawn forward and coiled up by machinery in a stationary po sition. The second method consisted in having the reels in a stationary frame, and conducting the yarns separately into one focus over to a revolving shaft or frame, in which the strand has to be wound up as made, and which contained the machinery for hauling forward the yarns which composed the strand. The hauling-forward machinery consisted of two rollers on a stationary and separate frame, close to the opening in the top of the revolving shaft, which twisted the yarn prepared for a strand, and contained the reel on which it was wound up. The two rollers by which the yarns were compressed and brought forward, drew them out to the same length, and prevented the yarn from being twisted into a mass. The strands thus made, were proved by public experiments to be greatly superior to those made by the old methods.
In the same year, viz. 1798, Mr. Balfour took out a second patent for improvements on his former method of manufacturing ropes, which was successfully tried in the king's yards, and for which he received a pre mium of some thousand pounds from the navy board. The backward motion of the sledge which was in troduced by Mr. Balfour, and which affords the most simple and perfect method of forming strands, led Mr. Chapman to the idea of regulating the motion of the sledge; so that for every revolution of the strand the sledge should move backwards through the exact length of axis assigned to it, and thus render the twist uniform. He therefore took out a patent in 1798, for his method of effecting this, which he thus describes: This object he attained, '' by stretching a rope, which he called a ground rope, the whole length of the ropery, and upon the floor of it. This rope was pass ed, in the form of an S, partially round two or more grooved wheels with horizontal axes, fixed with other apparatus on the common machine for making ropes, technically called a sledge, but which for that purpose is fitted with wheels to travel on a railroad. The grooved wheels press against each other to bind the rope, and have upon their axes toothed wheels, con necting them with each other, and finally with the hooks for turning the strands, which, in this instance, are all turned by one great crank, intervening between the hooks and the wheels appropriated to the back ward motion, and connected with the ground rope. Thus when the hooks were turned by the crank, the sledge was also drawn backwards, by the turning of the grooved wheels which received any determinate motion to that of the strand hooks, by means of changeable wheels easily taken off and on. In the pre ceding instance, the labour of the men is relieved by a rope leading from the sledge to a horse capstan, at the foot of the ropery. In consequence of the ground rope, (which is capable either of drawing the sledge forward, or retarding its motion,) the horse cannot draw the sledge faster than it ought to move; but his spare power is given in aid of twisting the strands through the intervention of the wheels, which connect that operation with the backward motion." Several ropeworks were erected under this patent on the river Tyne, Mr. Chapman having fitted up each ropery with all the apparatus for 560; and the ropes which were made were greatly superior to others. The strands made on the improved principle, were as strong as common made ropes, when the girt of the former was to that or the latter as 71 to 94 upon an average of 14 ropes, from 3 to 10 inches in girt; and the cables were as strong as common made ones, when the girt of the former was to that of the latter as 143 to 189 upon an average of 14 cables, from 51 to 20 inches in girt.