an instrument or machine of wood, chiefly employed in the rigging and other parts of a ship, by means of which a facility is given to the hoisting up or lowering down the masts, yards, and sails, or to the moving of any great weight, as guns, anchors, bales, casks, &c. It is, in fact, a modification of the pulley, and the names may almost be considered as synonymous.

There is nothing in the appearance of a block which, to an unpractised eye, would seem to require any stretch of mental ingenuity or of manual dexterity to manufacture. It is a machine apparently so rude in its structure, and so simple in its contrivance, that the name was probably given to it from its general resemblance to a log of wood, as is obviously the case with a butcher's block, a barber's block, the block of the executioner, &c. Of the two constituent parts of a ship's block, the external shell and the internal sheave, every carpenter might make the one, and every turner the other; and yet, when blocks were made by the hand, it seldom happened that the several parts were adjusted to each other with sufficient accuracy, or that a strict uniformity was observed in the various sorts and sizes, without which they cannot be expected to work with that degree of ease and truth, which is so desirable, and even necessary in the important office they are designed to fulfil, in the rigging and other parts of a ship.