BACK-ROPE. The rope-pendant, or small chain for staying the dolphin-striker. Also a piece long enough to reach from the cat-block to the stem, and up to the forecastle, to haul the cat-block forward to hook the ring of the anchor--similarly also for hooking the fish-tackle. (_See_ GAUB-LINE.) BACKS. The outermost boards of a sawn tree. BACK-STAFF. A name formerly given to a peculiar sea-quadrant, because the back of the observer was turned towards the sun at the time of observing its zenith distance. The inventor was Captain Davis, the Welsh navigator, about 1590. It consists of a graduated arc of 30° united to a centre by two radii, with a second arc of smaller radius, but measuring 6° on the side of it. To the first arc a vane is attached for sight,--to the second one for shade,--and at the vertex the horizontal vane has a slit in it. BACKSTAY-PLATES. Used to support the backstays. BACKSTAYS. Long ropes extending from all mast-heads above a lower-mast to both sides of the ship or chain-wales; they are extended and set up with dead eyes and laniards to the backstay-plates. Their use is to second the shrouds in supporting the mast when strained by a weight of sail in a fresh wind. They are usually distinguished into breast and after backstays; the first being intended to sustain the mast when the ship sails upon a wind; or, in other terms, when the wind acts upon a ship obliquely from forwards; the second is to enable her to carry sail when the wind is abaft the beam; a third, or shifting backstay, is temporary, and used where great strain is demanded when chasing, chased, or carrying on a heavy pressure of canvas: they are fitted either with lashing eyes, or hook and thimble with selvagee strop, so as to be instantly removed. BACKSTAY-STOOLS. Detached small channels, or chain-wales, fixed abaft the principal ones. They are introduced in preference to extending the length of the channels. BACKSTERS. Flat pieces of wood or cork, strapped on the feet in order to walk over loose beach. BACK-STRAPPED. As a ship carried round to the back of Gibraltar by a counter-current and eddies of wind, the strong currents detaining her there. BACK-SWEEP. That which forms the hollow of the top-timber of a frame. BACK-WATER. The swell of the sea thrown back, or rebounded by its contact with any solid body. Also the loss of power occasioned by it to paddles of steamboats, &c. The water in a mill-race which cannot get away in consequence of the swelling of the river below. Also, an artificial accumulation of water reserved for clearing channel-beds and tide-ways. Also, a creek or arm of the sea which runs parallel to the coast, having only a narrow strip of land between it and the sea, and communicating with the latter by barred entrances. The west coast of India is remarkable for its back-waters, which give a most useful smooth water communication from one place to another, such as from Cochin to Quilon, a distance of nearly 70 miles.