or CAPSTERN, a strong massive column of timber, formed like a truncated cone, and having its upper extremity pierced with a number of holes to receive the bars or levers. It is let perpendicularly down through the decks of a ship; and is fixed in such a manner, that the men, by turning it horizontally with their bars, may perform any work which requires any extraordinary effort.

A capstan is composed of several parts, where A is the barrel, b the whelps, c the drumhead, and d the spindle. The whelps rise out from the main body of the capstan like buttresses, to enlarge the sweep, so that a greater quantity of cable, or whatever rope encircles the barrel, may be wound about it at one turn, without adding much to the weight of the capstan. The whelps reach downwards from the lower part of the drumhead to the deck. The drumhead is a broad cylindrical piece of wood resembling a millstone, and fixed immediately above the barrel and whelps. On the outside of this piece are cut a number of square holes parallel to the deck, to receive the bars. The spindle or pivot d, which is shod with iron, is the axis or foot upon which the capstan rests, and turns round in the faucer, which is a sort of iron socket let into a wooden stock or standard called the flep, resting upon and bolted to the beams.

Besides the different parts of the capstan above explained, it is furnished with several appurtenances, as the bars, the pins, the pawls, the swifter, and the faucer, already described. The bars are long pieces of wood, or arms, thrust into a number of square holes in the drumhead all round, in which they are as the radius of a circle, or the spokes in the nave of a wheel. They are used to heave the capstan round, which is done by the men setting their breasts against them, and walking about, like the machinery of a horse mill, till the operation is finished.—The pins e, are little bolts of iron thrust perpendicularly through the holes of the drumhead, and through a corresponding hole in the end of the bar, made to receive the pins when the bars are fixed. They are used to confine the bars, and to prevent them from working out as the men heave, or when the ship labours. Every pin is fastened to the drumhead with a small iron chain; and that the bars may exactly fit their respective holes, they are all numbered.—The pawls f, No. 1, are situated on each side the capstan, being two short bars of iron, bolted at one end through the deck to the beams close to the lower part of the whelps; the other end, which occasionally turns round on the deck, being placed in the intervals of the whelps, as the capstan turns round, prevents it from recoiling or turning back by any sudden jerk of the cable, as the ship rises on the sea, which might greatly endanger the men who heave. There are also hanging pawls g, No. 3, used for the same purpose, reaching from the deck above to the drumhead immediately below it. The swifter is a rope passed horizontally through holes in the outer end of the bars, and drawn very tight; the intent of this is to keep the men steady as they walk round when the ship rocks, and to give room for a greater number to assist by pulling upon the swifter itself.

The most frequent use of the capstan is to heave in the cable, and thereby remove the ship or draw up the anchor. It is also used to wind up any weighty body, as the masts, artillery, &c. In merchant ships it is likewise frequently employed to discharge or take in the cargo, particularly when consisting of weighty materials that require a great exertion of mechanical powers to be removed.

There are commonly two capstans in a man of war, the main and the gear capstan; the former of which has two drumheads, and may be called a double one. This is represented in No. 3. The latter is represented in No. 2.

Formerly the bars of the capstan went entirely through the head of it, and consequently were more than double the length of the present ones; the holes were therefore formed at different heights, as represented in No. 1. But this machine had several inconveniences, and has long been entirely disused in the navy. Some of these sort of capstans, however, are still retained in merchant ships, and are usually denominated crabs. The situation of the bars in a crab, as ready for heaving, is represented in No. 4.

To rig the CAPSTERN, is to fix the bars in their respective holes, and thrust in the pins, in order to confine them.—Surge the CAPSTERN, is the order to slacken the rope heaved round upon it, of which there are generally two turns and a half about the barrel at once, and sometimes three turns.—To Heave the CAPSTERN, is to go round with it heaving on the bars, and drawing in any rope of which the purchase is created.—To come-up the CAPSTERN, is to let go the rope upon which they had been heaving.—To Pawl the CAPSTERN, is to fix the pawls to prevent it from recoiling during any pause of heaving.