Deep sea line block, is a small wooden snatch block, about from nine to eleven inches long.
Cheek blocks are half shells, bolted against the mast heads ; the chief bolt serves for the pin of the sheave they receive the halyards and stays of their respective masts.
• D blocks, are lumps of oak in the form of the letter D, from 12 to 16 inches long, and 8 or 10 feet wide ; they are bolted to the ship's side in the chan nels to receive the hits.
Long tackle block, are two single sheaves placed one above the other in the same shell. (See Fig. 3. Plate LVII.) The lower sheave is only the size of the other; it is used in combination with a common single block, to form the long tackle, for loading, or any other purchase. In the navy and East India service they are used as yard tackles. The rope is reeved through it in the same manner as it would be through a common double block ; but it is preferred where it is convenient, because the strap being in tfie centre of the resistance, it hangs more steadily than when the sheaves are on one pin.
Clue blocks. These are single sheaves sus pended from the yards by a strap with two eyes ; a lashing surrounds the yard and passes through the eyes, so as to suspend the block beneath the yard; these blocks receive the clue garnets or ropes which haul up the clues of the sail ; this is applied to the main and fore yard.
Clue line blocks are for the same purpose as the preceding, but applied to the top-sails, top-gallant, and sprit-sails. A great improvement has lately been made. in these blocks, by Mr Brunel, inventor of the block machinery at Portsmouth. The old clue line and clue garnet blocks, (for they are the same except in size,) was a single sheave block, strapped with two eyes as above ; a knot was made in the end of the clue line or garnet, just at the place where it was attached to the clue of the sail, to prevent the corner thereof be ing drawn into the block. This was not effective, and frequent inconvenience arose ; - for the sail being so constantly in motion, the rope had a great tendency to get entangled with the sail, and drawn over the sheave. The improved block in question is shewn in Plate LVIII. Fig. 1. The two holes at aa, are where
the rope goes in and out again. The sheave is si tuated in the centre of the block, so as to be wholly inclosed except a mortice at b, where the sheave is put in. The strap surrounds the lower part of the block ; then both ends pass through a hole in the up per part about c, crossing each other.' They are then formed into an eye, by which the block is suspended from the yard. By this means no accident can happen, as the garnet, or rope, is so inclosed in the block, that it cannot be deranged by any violence, nor the sail be drawn into the block.
Main sheet block is used for the sheet tackle of the main-sail-booms of small vessels. The pin projects from each side of the block, being in all the same length as the block ; the fail or rope of the tackle is belayed or twisted round this pin, to stop it. This block is either single or double, and has a hole through the end to receive its strap.
Monkey blocks are sometimes` used on the lower yards of small merchant ships, to lead (into the mast, or down upon the deck) the running rigging be longing to the sails. The shells are made of ash or elm. Some are only small single blocks attached by a strap and iron swivel to iron straps, which embrace and nail to the yard the block turning to lead the small running ropes in any direction ; others are near ly eight square, with a roller working in the middle, and a wooden saddle beneath to fit and nail to the yard. • Nine pin blocks are used to lead the running ropes in an horizontal direction. The shells, made of ash or elm, resemble the form of a nine-pin, though flat ted on the sides. Their lengths are generally confined to the place in which they are fixed ; and this is for the most part under the cross pieces of the fore castle, and quarter-deck bitts. The breadth of the block, sheave, &c. is governed by the rope, and ta per at the ends to three-eighths of the breadth of the middle; the pins at each end serving as a vertical axis, is two-thirds of the size of the end. The thick ness is five.cighths of the breadth. These blocks may be turned in a lathe, and flattened afterwards with a spoke sheave.