ROP

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ROP

voyed king Charles TIT. of Spain to Lisbon . In July, lie attack-ed Gibraltar; when, by the bravery ©f the English seamen, theplace was taken on the 24lh, though the town was extremelystrong, .well-furnished with ammunition, and had 100 guns mount-ed, all facing the sea and the narrow' passes to'the land : an actionwhich was conceived and exoiuted in less than aweek; yet wasthen very little thought of; though it has since endured sieges ofmany months’ continuance, andunore than once baffled the unitedforces of -France and Spain . This brave officer being obliged, byparty spirit, to quit the service of Iris country, retired to his seatin Kent; where, he enjoyed otium cum dignitate. He was thricemarried- 1 : and by his second lady, Mrs. Luttrell, left one son.He died January 24, 1708-9, in his 58th year, and was buriedin Canterbury cathedral , where a monument is erected to his me-mory.

ROOT, among botanists. See Botany , and Plant.

Root, in algebra and arithmetic, denotes any number which,multiplied by itself once or oftener, produces any other number;and is called the square, cube, biquadrate, &c. root, according tothe number of multiplications. Thus, 2 is the square root of 4;the cube root of 5 ; the biquadrate root of 16, &cc. See Arith-metic, and Algebra .

ROPE, is applied to a considerable collection of twisted fibres.Smaller bands are called lines, strings, or cords; and it is not ap-plied with great propriety even to those, unless they are composedof smaller things of the same kind twisted together. Two hay-bands twisted together would be called a rope, All the differentkinds of this manufacture, from a fishing-line or whip-cordto the cable of a first rale ship of war, go by the general name ofcordage.

ROPE-MAKING.

ROPE-MAKING is the art of making ropes and all kinds ofcordage. Rope-making is an art of great importance : and thereare few that better deserve the attention of the intelligent observer.Hardly any art can be carried on without assistance of the rope-maker. Cordage makes the very sinews and muscles of a ship ;and every improvement which can be made in its preparation,either in respect to strength or pliableness, must be of immenseservice to the .mariner, and to the commerce and the defence of na-tions. And therefore to a trading nation, such as Great Britain ,whose commercial and political importance depends upon its ship-ping, rope-making must be considered as of the utmost import-ance. Ropes are made of every substance that is sufficiently jfibrous,,flexible, and tenacious, but chiefly of the barks of plants, jThe Chinese and other orientals even make them of the ligneous jparts of several plants, such as certain bamboos and reeds, thestems of the aloes, the fibrous covering of the cocoa-nut, the fila-ments of the cotton-pod, and the leaves of some grasses, such asIhe sparte. (lygeum, Linn.) The aloe (agave, Linn.) and thesparte, exceed ail others in strength. But the barks of plants arethe most productive of fibrous matter fit for this manufacture.Those of the linden-tree (tilia,) of the willow, the bramble, thenettle, are frequently used : but hemp and flax are of all othersthe best; and of these the hemp is preferred, and employed in allcordage exceeding the size of a line, and even in many of thisdenomination. Hemp is very various in its useful qualities.These are great strength, and the length and fineness of the fibre.Being a plant of very greedy growth, it sucks tip much of theunaltered juices of the soil, and therefore differs greatly accord-ing to its soil, climate, and culture. The best in Europe comesto us through Riga , to which port it is brought from very distantplaces southward. It is known by the name of Riga rein (i. c.clean,) hemp. Its fibre is not the longest (at least in the dressedstate in which we get it) of all others; but it is the finest, most■flexible, and strongest. The next to this is supposed to be thePetersburg!! hraak hemp. Other hemps are esteemed nearly inthe following order: — Riga outshot, Petersburgh onbhot, hempfrom Koningshurg, Archangel, Sweden , Memel. Chucking is aname given to hemp that comes from various places, long in thefibre, but coarse and harsh, and its strength is inferior to thehemps which one woukl think weaker. The aim of the rope-maker is to unite the strength of a great number of fibres. Thiswould be done in the completes! manner by laying the fibres pa-rallel to each other, and fastening the bundle at the two ends ; buttins would be of very limited use, because the fibres are short, notexceeding three feet and a half at aw average. They must there-fore be entangled together, in such a manner that the strength ofa fibre shall not be able to draw it out from among the rest of thebundle. This is done by twisting or twining them together, wdiiehcauses them mulually to compress eacli other. When the fibresare so disposed in a long skain, that their ends succeed each other Jalong its length, w ithout many of them meeting in one place, andthis skain is twisted round and round, we may cause them to com-press each offer to any degree we please, and the friction on a;R>:e which we attempt to pull out may be more than its cohesion

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can overcome. It will therefore break. Consequently if we pullat this twisted skain, we shall not separate it by drawing one par-cel out from among the rest, but the whole fibres will break ; andif the distribution of the fibres lias been very equable, the skainwill be nearly of the same strength in every part. If there is anypart where many ends of fibres meet, the skain will break in thatpart. We can twist a skain of fibres so very hard, that it willbreak with any attempt to twist it harder. In this state all thefibres are already strained to the utmost of their strength. Sucha skain of fibres can have no strength. It cannot carry a weight,because each fibre is already strained in the same manner as ifloaded with as much weight as it is able to bear. What we havesaid of this extreme case is true in a certain extent of every degreeof twist that we give the fibres. Whatever force is actually ex-erted by a twisted'fibre, in order that it may sufficiently compressthe rest to hinder them from being drawn out, must be consideredas a weight hanging on that fibre, and must be deducted from itsabsolute strength of cohesion, before we can estimate the strengthof the skain. "The strength of the skain is the remainder of theabsolute strength of the fibres, after we have deducted the forceemploved in twisting them together. From this observation maybe deduced a fundamental principle in rope-making, that all twist-ing, beyond what is necessary for preventing the fibres from beingdrawn out without breaking, diminishes the strength of the cord-age, and should be avoided. It is of importance to keep this inmind. Spinning is the first part of the process, It is done invarious wavs, and with different machinery, according to thenature of the intended cordage. In the manufacture of the largerkinds, such as are used for the standing and running rigging ofships, an alley or walk is inclosed for the purpose, about 200fathoms long, and of a breadth suited to the extent of the manu-facture. Jt is sometimes covered above. At the upper end ofthis rope-walk is set up the spinning-wheel. The hand of thiswheel goes over several rollers called whirls, turning on pivots inbrass-holes. The pivots at one end come through the frame, andterminate in little hooks. The wheel being tinned by a winch,gives motion in one direction to all those whirls. 'The spinner liasa bundle of dressed hemp round his waist, with the two ends meet-ing before him- 'Die hemp is laid in this bundle in the way thatwomen spread the flax on the distjifl. r I here is great variety inthis; but the general aim is to lay the fibres so, that as long as tirebundle lasts, there may be an equal number of the ends at theextremity, and that a fibre may never oiler itself double or in abight. The spinner draws out a proper number of fibres, twiststhem with his fingers, and having got a sufficient length detached,he fixes it to the hook of a whirl. The wheel is now. turned, andthe skain is twisted, becoming what is called a rope-yarn, and thespinner walks backwards down the rope-walk. The part alreadytwisted draws along with it more fibres out of the bundle, Th espinner aids this with his fingers, supplying hemp in due propor-tion as lie walks away from the wheel, and taking care that thefibres come in equally from both sides of his bundle, and that theyenter always with their ends, and not by the middle, which woulddouble them. Rope-varns, for the greatest part of the larg®

rigging-