BLOCK

A common single block is composed of three parts; the shell, the sheave, and the pins. The shell, arcasse, approaches nearest to the figure of a long spheroid, somewhat flatted in the middle. Between the two flat sides it is hollowed so as to receive a narrow cylindrical wheel called the sheave, rouct, formed of lignum-vitae, or other hard wood; and through the center of this sheave is bored a round hole to admit of a pin, which is driven through two corresponding holes in the middle of the shell, perpendicular to the hollow space within. The pin thus becomes the axis of the wheel or sheave, which completes the wooden work of the machine. Thus formed, it is bound with a sort of rope-ring, which is closely fitted to a notch passing round the surface of the shell, and over both ends of the pin: and by this ring, or wreath, which is called a block-strop, they are suspended upon the masts, shrouds, &c.

The complicated blocks, or those which contain a number of wheels, either have all the wheels to run upon one axis, (see plate I.) or have their shells so formed that the wheels are one above another. In the former shape they approach nearest the figure of a cylinder, and in the latter appear like two or more single blocks joined together endways.

Plate I

In plate I fig. 7. a, represents a single block, and b, c, two double ones, of different kinds, without strops. Fig. e, f, two double tackle blocks iron-bound, the lower one, f, being fitted with a swivel; g, a double iron-bound block with a large hook; h, a snatch-block; i, a top-block; k a voyal-block, and l, a clue-garnet-block. See SNATCH-BLOCK, TACKLE, and VOYAL.

Reference Works