DHOW. The Arab dhow is a vessel of about 150 to 250 tons burden by measurement--grab-built, with ten or twelve ports; about 85 feet long from stem to stern, 20 feet 9 inches broad, and 11 feet 6 inches deep. Of late years this description of vessel has been well built at Cochin, on the Malabar coast, in the European style. They have a great rise of floor; are calculated for sailing with small cargoes; and are fully prepared, by internal equipment, for defence--many of them are sheathed on 2-1/2-inch plank bottoms, with 1-inch board, and the preparation of chunam and oil, called _galgal_, put between; causing the vessel to be very dry and durable, and preventing the encroachments of the worm or _Teredo navalis_. The worm is one of the greatest enemies in India to timber _in_ the water, as the white ant (_termites_) is out of it. On the outside of the sheathing board there is a coat of whitewash, made from the same materials as that between the sheathing and planks, and renewed every season they put to sea. They have generally one mast and a lateen sail. The yard is the length of the vessel aloft, and the mast rakes forward, for the purpose of keeping this ponderous weight clear in raising and lowering. The tack of the sail is brought to the stem-head, and sheets aft in the usual way. The halyards lead to the taffrail, having a pendant and treble purchase block, which becomes the backstay, to support the mast when the sail is set. This, with three pairs of shrouds, completes the rigging, the whole made of _coir_ rope. Several of these vessels were fitted as brigs, after their arrival in Arabia, and armed by the Arabs for cruising in the Red Sea and Arabian Gulf, as piratical vessels. It was of this class of vessel that Tippoo Sultan's navy at Onore consisted. The large dhows generally make one voyage in the season, to the southward of Arabia; taking advantage of the north-east monsoon to come down, and the south-west to return with an exchange cargo. The Arabs who man them are a powerful well-grown people, and very acute and intelligent in trade. They usually navigate their ships to Bengal in perfect safety, and with great skill. This was well known to Captain Collier and his officers of the _Liverpool_ frigate, when they had the trial cruise with the Imam of Muscat's fine frigate in 1820. DIACLE. An old term for a boat-compass. DIAGONAL BRACES, knees, planks, &c., are such as cross a vessel's timbers obliquely. (_See_ DIAGONAL TRUSSING.) DIAGONAL RIBBAND. A narrow plank made to a line formed on the half-breadth plan, by taking the intersections of the diagonal line with the timbers. (_See_ RIBBANDS.) DIAGONALS. A line cutting the body-plan diagonally from the timbers to the middle line. Diagonals are the several lines on the draughts, delineating the station of the harpings and ribs, to form the body by.