Signal-halyards stuff is made of strands that have been laid up in opposite ways, so as to lessen that tendency to taking in turns which is so inconvenient in hoisting flags.* It is laid up in lengths of 113 fathoms, and from to 1 inch in circumference. BLOCKS. Blocks of ships are made of elm, having either metal or lignum vitæ sheaves, with a metal bouching and iron pin. Their size is denoted by the length of the shell, and their quality by their degree of flatness or thickness, number of sheaves, scores for stropping, and nature of stropping. For instance, a brace block is (say) 20-inch, single, thin, and double scored. A tye block is, single, thick, and iron bound. Clump Blocks are made shorter and thicker, and have metal sheaves, which are smaller in diameter than those of other blocks which reeve the same sized rope. Tack and sheet blocks are of this description. Shoulder blocks are made with a projection left on one side of the top of the shell, which bearing against the place of connection, prevents the falls from being jammed. Such are Purchase and Fore tack blocks. The Fiddle block is a large and small single block made on end in one piece, each being equally large in the swallow. The parts of rope are kept more clear of each other in this kind of block, and as they do not cross, there is less friction; but as the upper sheave is smaller in diameter, there is a loss of power. Sister blocks are also two in one on end, but are of the same size. They are only used where two different ropes lead from similar directions, but well apart, as in the case of topsail lifts and reef-tackles. Strop bored blocks have a projection left on each side of the lower part of the shell, through which the strop passes, and which is supposed to keep small gear out of the swallow. They are used for reef-tackles and clue garnets. Iron stropped blocks have either a swivel or standing hook. In the case of snatch blocks, the binding is cut through to * In fitting flags, Sennit distance lines are less liable to take turns than is rope of any other kind. receive the rope, and is connected by a clamp, which should be locked whenever the rope is rove. Blocks should frequently be examined, not only as to strapping, but also by knocking the pin out, and inspecting the bouching. The loss of power, and strain on rope occasioned by a worn bouch is considerable. The working blocks of tackles, (for instance, the fly-block of top-sail halyards) are always more worn than the lower ones, and therefore without waiting until the sheaves shriek and become dumb, the blocks should be shifted or the sheaves transposed. This remark applies also to quarter-davits. That sheave on which the hauling part of the rope works does most duty for although it is assumed in mechanics that strain is equally born by all parts of a rope in a tackle, practice proves that the hauling part is most worn and strained, If, for example, we have a weight of 3 cwt. suspended by a luff-tackle, the upper block being fixed, and we hang a weight of 1 cwt. to the fall, the 3 cwt. would be balanced, but the fixed block would bear a weight of four cwt. And there is something of this kind which calls for greater strength, and frequent alteration in upper blocks (see p. 118). All blocks which stand horizontally-as lower brace blocks→ must be placed with the square end of the pin upwards; as, when the shell shrinks, it is liable to fall out if placed otherwise. Hanging, Tye, and Quarter blocks undergo great strains when bracing sharp up; if the former are two blocks, the weather halyards should be eased up sufficiently. Cat Blocks are liable to split, if not unhooked before fishing the anchor. So are Jeer Blocks, if hove together, as sometimes happens in the excitement of heaving up lower yards. The Language of Blocks is a most useful study. When their natural desire to "look to their work " is not gratified, they complain loudly. "If that block could speak, what would it say?" was a favourite question of a celebrated old officer who was not friendly to the over neat rigging mania that obtained in those times, when foot-ropes were stopt up, and gear was unrove to make a ship look "nice." There is a regular proportion for the size of rope stropping; and the blocks are fitted either with a hook and thimble, a lashing eye, or with a tail. The splice of the strop is always placed at the lower part of the block. A block is double stropped when it is desirable to give it a ! different stand to what it would have with a single one, as in the case of brace blocks. Gun Tackle Blocks are usually stropped with a grummet. One man can fit about 11 of these in a day of 9 hours' work: or 12 common, serving his own strop. Blocks should be three times the size of the rope rove in them. The standing part of the rope in small tackles is either spliced into the strop of one of the blocks, or clenched into a becket in the strop. In the latter way, the rope can more readily be temporarily applied to other purposes, or disconnected or stowed away in places which might be too small to contain the blocks also. In the case of two fold blocks, the splice or becket is placed on one side of the lower part of the strop, so that the standing part of the fall may look straight into its reeve. In the case of large tackles, the standing part of the fall is brought up alongside the fixed block and secured either round the neck of its strop, or to the place at which the block is attached. When the standing part is made fast at the moving block, it is generally rove through the becket and clenched round the neck of the strop. This keeps the block upright whilst overhauling down, and prevents a "Thorofoot." In either mode of applying the tackling, the block will be relieved of some strain by taking the standing part to the fixture or to the weight. Block strops if covered at all, should be so with matting laced on. A pointed strop is seldom dry; soon decays invisibly, and breaks without warning. The largest sized blocks made in one piece are 28 inches. Careening blocks, which are built, are as large as 42 inches, and are usually made with metal sheaves. The principal objection to many fold blocks is that the partitions cannot without being unwieldy be made thick enough to resist great pressure at the middle part of the pin. Upon the perfect straightness of which pin diminution of friction greatly depends. TABLE of the size and weight of purchase blocks, and the number allowed to each rate. Hooks. There are no rules laid down for the relative proportion of hooks to blocks, and as they Fig. 75. Figures 76, 77, 78, and 79, represent sections of hooks at their curved parts on a scale of half the actual size. These proportions have been adopted in the iron factories, and are warranted to bear the weights noted on each. As the inner fibres of the curve are exposed to a tearing asunder strain, whilst the outer bear only a crushing strain, the upper edges of these hooks are thickest. Metal Blocks being very much shorter in the shell than wooden, are frequently used under circumstances in which wooden ones would for want of space be impossible or inconvenient, such as steering gear, lifting machinery, mounting and dismounting guns. They are also used as quarter blocks in ships fitted with chain top-sail sheets. Thimbles are made both perfectly round, and also with the ends nearly joined. Two are sometimes united for the purpose of giving easy play to the adjoining strops or block, as well as a different stand; as in fitting lower and top-sail brace blocks. * One great advantage in Bothway's blocks is, that the hook may be unshipped and a shackle substituted at pleasure. M |