OROUND TACKLK. 



OROUNn TACKLK. 



(or select committee * to inquire into the manufacture of anchors 

 Mid chain cables for the merchant senric*," and the motion wa agreed 

 to on the '2nd of February, 1864. 



The writer rememben the time when the chain cable had not sup- 

 planted that of hemp. In thoee davm, not half a century distant, the 

 EaU Indiaman, the deeply-laden West Indiaman, the) burdeneome 

 collier, and even the line-of-battle ahip, were eeen in that far-famed and 

 dreaded roadstead, " the Down*,* on the Kentish coast, plunging to 

 the itrain of a long cope of hempen and "coir* cable*, driving 

 onwar 1* again through (urge and mirf to the point of mean tendon, 

 from which a huge lea occasionally hurled them ; the rlattirity of the 

 cable* acting like a spring against the sudden blow from a huge ware 

 sufficient to sweep the decks and cause the ship to tremble. It is well 

 to contrast this with the preeent system. At the time when the chain 

 table was merely an attractiTe experiment, the oldest piloU and seamen 

 were of opinion that its rigidity would in bod weather tear the bows 

 from a hip, eren from the strongest. For yean it was remarkable 

 that until ships were strengthened for the purpose, the capsizing of 

 the windlass [\VWDI.ASS] was a circumstance of more frequent occur- 

 rence ; and it was only when public attention was drawn by chain 

 makers to the fact, that the weight of the submerged chain itaelf, 

 hanging in a curve, in some measure modified the shock of a sudden 

 tension, that the ship-owners consented to fit their ships with a cer- 

 tainly more compact and more manageable cable, such as we have in 

 use at the preeent day. The liability of the old cables to be destroyed 

 by chafing in rocky anchorage grounds, frequently occasioned the loss 

 of shipping. The necessity of anchoring in such unfavourable places 

 might occur several times in the course of a long voyage, and not only 

 would danger be incurred on each occasion, but there was the risk of 

 a ship being compelled, owing to the loss of anchors, to pursue her 

 coarse destitute of the usual means of security. The action of thu 

 water upon hemp, and its being alternately exposed to the air and 

 water, rendered in time the strongest cables rotten and insecure. The 

 idea of substituting Iron cables first occurred to M. Bougainville, who 

 made a voyage round the world, an account of which was published in 

 1771. The idea was not taken up until 1808, when Mr. Slater, a 

 surgeon in the navy, took out a patent for a chain-cable. Its merits 

 were not much valued until Capt. Brown, who had made experiments 

 with chain-cables which enabled him to form a just opinion of their 

 advantages, published tho results, and thus directed the attention of 

 naval men to their superiority. The Admiralty soon after ordered 

 them to be tried in the navy. In 1812, Mr. Brunton obtained a patent 

 for further improvements ; and after the war he enjoyed a brent for 

 im|>orting chain-cables into France, but the advantages which he de- 

 rived from it were so small that he relinquished his privilege. 



Chain-cables are now furnished with bolts at the distance of 10 or 

 15 fathoms from each other, by withdrawing which a ship may slip 

 her anchor in case of necessity with less trouble than was formerly 

 required in cutting a strong hempen cable. 



Chain-cables are of various kinds, but one general description of 

 the mode of manufacture will suffice. The efficiency of a cable is 

 dependent on two operations widely distinct, namely, the forging and 

 the letting. For large chains a piece of iron bar, seldom larger than 

 2J inches diameter, is cut to the proper length for a link, and is shaped 

 : i ing like ti>j. 1 . It is also during the cutting, and by means of a 

 powerful revolving dine, bnt into the form fig. 2. It is then ready for 

 the chain-smith, who is necessarily a well-skilled workman, who care- 

 fully welds the two ends together, introducing at the time the cast- 

 iron stud, fig. 8, the complete link having the form in fig. 4 ; other 

 links are shut on to this in the same manner, until the ponderous 

 chain, often of about 12 tons weight, is ready for the next process, 

 that of testing. The perfect welding of the two ends of the bar, is by 

 all respectable anchor-smiths mode a subject of pecuniary interest to 

 the workmen themselves, since a failure in a link under testing involves 

 to them loss of time and expense in replacement. 



Small vessels use a chain without a stud, the links arc vnri'.n.-ly 

 proportioned to the thickness of the bar, the " short link " having the 

 appearance of fig. 6. 



From the great care bestowed on the manufacture of chain-cables by 

 such houses as Wood ft Co., of Saltncy, the Tyne Works, ami otlj,-r 

 eminent in-the trade, it is doubtful if much improvement ) rein can 

 be consistently hoped for. Such firms having their own testing-bouses, 

 usually give a certificate with their best chains ; but the question arises 

 as to how far a Htmd testing by public machines, such at at Liverpool, 

 Smderltmd, Ac., is judicious 1 



Professor Hodgkinion gives the tensile strength of wrought-iron as 

 24 tons to the square inch of section. Now the sectional arc' of a 2} 

 inch chain will be 3-S8 square inches, and therefore the maximum of 

 breaking itrain which such a chain is calculated to bear is about 96| 

 tons. But the question was strongly urged by Mr. Saxby in 1855 (see 

 ' Nautical Mag.'), whether the amount of proof required by the govern- 

 ment were not the cause of frequent failure of a chain from orrr fating. 

 It is significant that Sir J. ElphinstoBe has just stated hi the House of 

 Commons, that in the public testing machines at Liverpool 82 per cent. 

 of the chain-cables tried there had broken I 



A few considerations on the operation of testing a metal may be 

 useful Especially should we investigate the probable effect of testing 

 on the atoms [ ATOMS] of which tile iron (or metal) is composed. 

 If we view the subject as a mere case" of itrain and resistance, we con- 

 fine our scrutiny to a dangerous limit Let us suppose it possible that 

 the following figure represents a minute portion of a substance, say of 

 wood or iron : 



Imagine tho dots to be atoms enormously magnified. It is supposed 

 that in all solids atoms arc in approximation only, not in contact ; that 

 equilibrium is produced among these atoms by innate counteracting 

 forces, attractive and repulsive. Let the circles surrounding the 

 dots represent the limit of attraction for each atom while in equili- 

 brium : suppose, for example, such dots are the atoms of a lancewood 

 bow. If we cast arrows from it during, say, an hour, we shall on 

 unstringing it find that if the arrows have been projected by means of 

 nulden jerks, the bow will sooner recover its original shape than if such 

 arrows had been thrown by a d'>tdy drawn force ; and moreover we 

 shall find that the arrows in the former case will reach a more distant 

 object than in the latter : hence we infer thjit the bow will bear a 

 much greater strain with impunity in the first case than hi the second. 

 And thus it is with the testing of a chain-cable by the slow method in 

 use. But to return to tho bow.; the common phrase " lotting it* 

 elasticity " is very significant when applied to iron, whieh in this respect 

 differs from wood, the one being ductile, the other not ; hence a piece 

 of wood bent so much as to draw ita atoms farther apart than the 

 imaginary circles in Jig. 6 permit, or to separate its atoms beyond the 

 sphere of each other's attraction, as shown at a, 6, in fig. 6, becomes 

 " broken," unless a restoration of position go sudden as to retard the 

 re-arrangement which the disturbance of electric, or galvanic, or 

 calorific agencies induce, it possible ; and in tho case of wrought-iron, 

 this re-arrangement is supposed to commence when the tension amounts 

 to about ten tons to the square inch of sectional area ; and this can 

 only take place at the cost of the metal's so-called " elasticity ; 

 changes in the iron depending upon a supposed polarity imparted to 

 its atoms, by disturbance of electric currents made evident by the 

 production of sensible magnetism. 



The iron thus becomes comparatively " brittle," and consequently 

 less able to resist even the proof-strain which, in the first instance, it 

 may have borne with safety. 



Does it not appear then that an iron chain cable, in being subjected 

 to a tcrond test, must become materially weakened 1 It is remarkable 

 that, although we speak of iron becoming " permanently " Htretc-lu -<1 I <y 

 a strain of upwards of 10 tons, such is merely conditional, because the 

 judicious application of a red heat has, in the well-known process of 

 annealing, the effect of restoring a state of equilibrium, a fact bearing 

 strongly upon a consideration of the very nature of electricity ittelf. 

 That the greatest strain which affects a ship's cable is in some measure 

 favourable to the " restoration in position " of the molecules of the 

 iron, may bo understood from the following unexaggerated sketch. It 

 is not the riding of a ship in a mere tide-way that usually tries a cable 

 to the utmost; but it is the tremendous sudden jerks which a cable 

 sustains when (as in Jig. 7, c.) a ship is checked by her ground-tackle 

 when on the very crest of a wave. The moment the wave has passed, 

 the weight and " elasticity " of the chain [if not destroyed by over- 

 letting), together with the weight of the metal in suspenxion from tho 

 shock, gives the ship an onward impulse which lessens the shock of tin- 

 next wave (sailors believe in what they call " master-waves ") ; thus 

 the chain has time to partially recover its atomic equilibrium : this 

 may be seen in the altered angle at which the cable hangs from the 

 hawse, as shown in jig. 7 d. 



It would seem from the above remarks that, to lessen the dangers 

 which at present affect ground-tackle, so far as they result from the 

 breaking (or " parting," as it is cal!e.l i t Mi.- chain-cable, thu following 

 point* demand the deepest consideration : 



1. It '/ correct totttta chain to a amount far beyond 10 torn to the 

 inch sectional area ! 



2. Should a chain ever be tetttd a second time I 



