The masts of ships are built of several pieces selected from the strongest parts of trees, and attached together both in the fore-and-aft and in the athwart-ship directions, the whole being bound together by hoops at intervals. Usually the central piece consists of one log of timber reduced to a many-sided form, and to the sides of this are applied other pieces, which are connected with it either by a longitudinal projection in each, which is let into a corres ponding channel made in the central piece, or by blocks of hard wood which are let into both the central and attached pieces.
Vessels of iron are now very frequently con structed both for rivers and for navigation in tho open seas, and they have many advan tages over ships of wood. They are much lighter, or more buoyant. They are less liable to become arched, and are better able to with stand the effects of striking upon a rock. In the latter case a ship of wood would have its bottom pierced, or it might go to pieces, while the iron one would merely become indented. They are formed with rib frames at intervals, and with longitudinal hoops of iron ; and they are covered with iron plates, which are fastened to the ribs by bolts or rivets. The lower part of the interior may be divided into compart ments, which can be rendered air-tight; and thus, in the event of the bottom being perfo rated in any place, the water would be con fined within that compartment till the damaged plate could be repaired or replaced.
Ships have different designations, according to the number of their masts or the disposi tion of their sails. The word ship is more particularly applied to those vessels which have a fore, a main, and a mizen mast, with a top-mast and top-gallant-mast to each ; and in which the yards, in sailing before the wind, are braced square, that is, in vertical posi tions perpendicularly to the length of the ship the mizen-sail alone being usually in a fore and.aft position, that is, in a vertical plane passing through the keel. A bark is a vessel with masts and sails like those of a ship, ex cept that the mizen-mast carries no top-sail or top-gallant sail. A brig has a fore and a main mast, with top and top-gallant masts and sails, like those of a ship ; but it has no mizen-mast, and the main-sail has a position corresponding to that of the mizen•sail in a ship with three masts. A snow is rigged in the same manner as a brig, except that the main-sail is attached to a small mast abaft of and very near the main-mast. A schooner has
two masts, and the sails attached to them are, in their usual position, in vertical planes pass ing through the keel : it has small or no top sails. Lastly, a sloop (sbaloop) has only one mast, with a main-sail, whose plane is usually in a fore-and-aft position. Each of the dif ferent kinds of ships has a bowsprit which carries a fore-stay-sail and a jib-sail.
In the British navy, ships which carry 70 or a greater number of guns are called line-of battle ships. Frigate is a term which is sup posed to have been first, applied to a light galley moved by sails or oars ; but it is now applied to ships of war, generally with two decks, and carrying from 36 to 60 guns. These are built narrower than line-of-battle ships in proportion to their length, and sail swiftly. They accompany fleets in order to watch at a distance the movements of the enemy, and they act singly against ships of a like kind. Ships of war of a lower class than frigates have the denominations of sloops, corvettes, !wigs, cutters, brigantines, ketches, schooners, and 5er/es. The sloops of war and corvettes carry 1.om 4 to 20 guns, and some, brigs carry 16 pins. The number of guns in a vessel of tither of the remaining classes does not ex leed 10.
The tonnage of a ship is, properly, an xpression for the interior capacity by the lumber of tons of sea-water which it could :ontain; therefore, if the interior volume were sound in cubic feet, on dividing that volume.
35 (the number of cubic feet of sea-water which are equal in weight to one ton), the quotient would be the tonnage required. There have, however, been various modes of esti mating ships' tonnage.
There are now employed in the yearly transit of Great Britain with the world and with her own shores, about 33,700 sailing vessels, and 1150 steam vessels, employing 240,000 seamen. Calculating the value of each ship and cargo, as the value has been estimated before parliament, at 50001., we have an aggregate value—sailing vessels, steamers, and their cargoes included—of about 174,000,000/. Further, supposing that the yearly wages of the seamen, including officers, was 20/. per head, the amount paid in wages would be 4,800,000/.
Various details bearing more or less closely on the subject of ship-building will be found under ANCHOR; BLOCKS; RIGGING; ROPE MANUFACTURE; SAIL MAKING; SCREW PRO PELLER ; SHEERS ; STEAM VESSEL ; &C.