J.
JACK, a sort of flag or colours, displayed from a mast erected on the outer end of a ship’s bowsprit. In the British navy the jack is nothing more than a small union flag, composed of the intersection of the red and white crosses; but in merchant ships this union is bordered with a red field. See the article Union.
JAMMING, the act of inclosing any object between two bodies, so as to render it immoveable, whilst they continue in the same position. This expression is usually applied to the situation of some running-rope, when it happens to be squeezed by the compression of the standing-rigging, &c. and by consequence incapable of performing its office, by traversing in the blocks, till it is released from this confinement. In this sense jamming is opposed to rendering, which see.
A cask, box, &c. is also said to be jammed, when it is in the same manner wedged in between weighty bodies, so as not to be dislodged without great difficulty.
JEARS, or GEERS, drisse, an assemblage of tackles, by which the lower yards of a ship are hoisted up along the mast to their usual station, or lowered from thence as occasion requires; the former of which operations is called swaying, and the latter, striking. See those articles.
In a ship of war, the jears are usually composed of two strong tackles, each of which has two blocks, viz. one fastened to the lower-mast-head, and the other to the middle of the yard. The two blocks which are lashed to the middle, or slings of the yard, are retained in this situation by means of two cleats, nailed on each side, whose arms enclose the ropes by which the blocks are fastened to the yard. The two ropes, which communicate with these tackles, lead down to the deck on the opposite side of the mast, according to the situation of the upper jear-blocks.
The jears, in merchant-ships, have usually two large single blocks on the opposite side of the mast-head, and another of the same size in the middle of the yard. The rope, which communicates with these, passes through one of the blocks hanging at the mast-head, then through the block on the yard, and afterwards through the other hanging-block upon the mast. To the two lower ends of this rope, on the opposite sides of the mast, are fixed two tackles, each of which is formed of two double blocks, the lower one being hooked to a ring-bolt in the deck, and the upper one spliced, or seized into the lower end of the great rope above, which is called the tye. By this contrivance the mechanical power of the tackle below is transmitted to the tye, which, communicating with blocks on the yard, readily sways up, or lowers it, either by the effort of both jears at once, on the opposite sides of the mast, or by each of them separately, one after the other.
JETTY-HEAD, a name usually given, in the royal dock-yards, to that part of a wharf which projects beyond the rest; but more particularly the front of a wharf, whose side forms one of the cheeks of a dry or wet dock.
JEWEL-BLOCKS, a name given to two small blocks, which are suspended at the extremity of the main and fore-top-sail-yards, by means of an eye-bolt, driven from without into the middle of the yard-arm, parallel to its axis. The use of these blocks is to retain the upper-part of the topmast studding-sails beyond the skirts of the top-sails, so that each of those sails may have its full force of action, which would be diminished by the incroachment of the other over its surface. The haliards, by which those studding-sails are hoisted, are accordingly passed through the jewel-blocks; whence, communicating with a block on the top-mast-head, they lead downwards to the top or decks, where they may be conveniently hoisted. See the article Sail.
JIB, foc, the foremost sail of a ship, being a large stay-sail extended from the outer end of the bowsprit, prolonged by the jib-boom, towards the fore-top-mast-head. See Sail.
The jib is a sail of great command with any side-wind, but especially when the ship is close-hauled, or has the wind upon her beam; and its effort in casting the ship, or turning her head to leeward, is very powerful, and of great utility, particularly when the ship is working through a narrow channel. See Sailing.
Jib-Boom, a boom run out from the extremity of the bowsprit, parallel to its length, and serving to extend the bottom of the jib, and the stay of the fore-top-gallant-mast. This boom, which is nothing more than a continuation of the bowsprit forward, to which it may be considered as a top-mast, is usually attached to the bowsprit by means of two large boom-irons, (see the article Iron-Work) or by one boom-iron, and a cap on the outer-end of the bowsprit; or, finally, by the cap without, and a strong lashing within, instead of a boom-iron; which is generally the method of securing it in small merchant-ships. It may therefore be drawn in upon the bowsprit, as occasion requires, which is usually practised when the ship enters a harbour, where it might very soon be broke, or carried away, by the vessels which are moored therein, or passing by under sail.
JIBING. See Gybing.
JIGGER, a machine, consisting of a piece of rope about five feet long, with a block at one end and a sheave at the other; and used to hold-on the cable, when it is heaved into the ship by the revolution of the windlass. See Holding-on.
The jigger is particularly useful when the cable is either slippery with mud or ooze, or when it is stiff and unwieldy; in both of which cases it is very difficult to stretch it back from the windlass by hand, which however is done with facility and expedition, by means of the jigger, as follows: the end of the rope, to which the sheave is fastened by a knot, is passed round the cable close to the windlass, and the hind part of the rope coming over the sheave, is stretched aft by means of another rope passing through the jigger-block. As soon as the last rope is extended, the turn of the former about the cable is firmly retained in its position, by the compression of its hind part under the sheave, acting upon what may be called the neck of the jigger. But as the cable continues to be heaved into the ship, it is evident that the jigger, which is fastened on a particular part thereof, stretching it back, will be removed further aft, by every turn of the windlass, and the effort of the jigger will be lessened in proportion to its distance from the windlass: this circumstance renders it necessary to fleet it, or replace in a proper state of action, as occasion requires. The man who performs this office accordingly calls out, fleet, jigger! one of the men, at the windlass, instantly fixes his handspec between the deck and the cable, so as to jam the latter to the windlass, and prevent it from running out till the jigger is refixed.
Jigger-Tackle, a light small tackle, consisting of a double and single block, and used on sundry occasions by seamen. See Tackle.
IN, dedans, the state of any of a ship’s sails, when they are furled or stowed. It is used in this sense also in opposition to out, which implies that they are set, or extended to assist the ship’s course.
INSURANCE, assurance, a certain contract, by which an individual, or company, agrees to indemnify whatever losses or damages may happen to a ship or cargo, during a voyage, provided they are not occasioned by default of the person insured. For this agreement the latter pays a certain sum in advance, called the præmium, which accordingly falls to the insurer, in case the ship arrives in a safe harbour; but if the ship is lost, the insurer renders the stipulated sum to the merchant.
JOURNAL, in navigation, a sort of diary, or daily register of the ship’s course, winds, and weather; together with a general account of whatever is material to be remarked in the period of a sea-voyage.
In all sea-journals, the day, or what is called the 24 hours, terminates at noon, because the errors of the dead-reckoning are at that period generally corrected by a solar observation. The daily compact usually contains the state of the weather; the variation, increase, or diminution of the wind; and the suitable shifting, reducing, or enlarging the quantity of sail extended; as also the most material incidents of the voyage, and the condition of the ship and her crew; together with the discovery of other ships or fleets, land, shoals, breakers, soundings, &c.
The form of keeping journals is very different in merchant-ships; but one method appears to be invariably pursued in the navy, which nevertheless is certainly capable of improvement, because no form can be properly called perfect, that leaves as great a space for one day’s work, the matter of which may be contained in very few lines, as for another that abounds with important incidents, so as to occupy ten times the space. If therefore there be any such thing as propriety of method on this occasion, it seems to imply, that the space containing, should conform to the matter contained, which will necessarily be greater or less, according to circumstances.
IRON-WORK, ferrure, a general name for all the pieces of iron, of whatsoever figure or size, which are used in the construction of a ship: as bolts, boom-irons, nails, spikes, chains and chain-plates, block-strops, cranks, braces, pintles, and googings.
The most material of these articles are explained in their proper places; but as the article bolt, of which the figures are represented in plate [II]. was accidentally omitted in the proper place, according to the plan of this work, it may not be improperly introduced here.
A bolt then is generally a cylindrical pin of iron, of which there are various sorts, used for sundry occasions in ship-building.
The bolts are principally employed either to unite several members of a ship’s frame into one solid piece, or to fasten any moveable body on a particular occasion. Those which are calculated for the former purpose have commonly small round heads, somewhat flatted, as in fig. 1 & 2. plate [II]. On the contrary, the bolts which are intended for the latter use, have either a large round head, as those of the chains, fig. 4. or an eye, with or without a ring in the same place, fig. 5, 6, and 39, as those which are designed to secure the great guns, the jears of the main-sail and fore-sail, the stoppers of the cables, &c.
The bolts are short or long, according to the thickness of the timber wherein they are to be lodged: they penetrate either quite through the pieces into which they are driven, or to a certain determinate depth. The last of these, called a rag-bolt, is retained in its situation by means of several barbs, fig. 3. which, fastening into the timbers, prevent the bolt from loosening from its station by the working of the ship. The first, after being driven through the pieces it is intended to unite, is confined by a flat iron wedge, called the forelock, which is thrust through a narrow hole in the small end of the bolt, where it is hardened home by a hammer; and to prevent the forelock from cutting the wood-work in this position, a little iron ring is fixed over the end of the bolt, between the forelock and the timber.
Those bolts, which have the largest of the round-heads, are called fender-bolts, being driven into the wales, stem, or sides of some small vessels of burthen, as lighters, beancods, prames, &c. to defend their timber-work from the shock of any other vessels which may fall aboard by accident.
A boom-iron is composed of two iron rings, formed into one piece, so as nearly to resemble the figure of 8. It is employed to connect two cylindrical pieces of wood together, when the one is used as a continuation of the other; such is the jib-boom to the bowsprit; and such are the studding-sail booms to the respective yards from whose extremities they are prolonged. The rims, or circles of the boom-irons, are broad and flat; and one of them, which is firmly driven upon the main, or fore-yard-arm, is somewhat larger than the other, as exhibited in fig. 7. plate [II]. The studding-sail-boom usually rests in the small ring, through which it is occasionally thrust outwards from the yard-arm, when the studding-sail is to be set. Every boom of this kind has, or ought to have, two boom-irons, one of which is fixed on the extremity of the yard, and the other further inward. The former of these is frequently framed of one ring only, which projects from the end of the yard, where it is fastened by a strong iron bar, opening into a sort of fork or crotch that slides upon the yard lengthwise, where it is fastened by nails driven from above and below.
ISLAND of ICE, a name given by sailors to a great quantity of ice collected into one huge solid mass, and floating about upon the seas near or within the arctic circle.
Many of these fluctuating islands are met with on the coasts of Spitzbergen, to the great danger of the shipping employed in the Greenland fishery.
JUNK, bouts de cable, a name given to any remnants or pieces of old cable, which is usually cut into small portions for the purpose of making points, mats, gaskets, sennit, &c. See Points, &c.
JURY-MAST, a temporary or occasional mast, erected in a ship to supply the place of one which has been carried away by tempest, battle, or the labouring of a ship in a turbulent sea.