BLOCKS AND PURCHASES.
Parts of a block. Made and morticed blocks. Bull's-eye. Dead-eye.
Sister-block. Snatch-block. Tail-block. Whip. Gun-tackle. Luff-tackle.
Whip-upon-whip. Luff-upon-luff. Watch or tail-tackle. Runner-tackle.
Blocks are of two kinds, _made_ and _morticed_. A _made block_ consists
of four parts,--the _shell_, or outside; the _sheave_, or wheel on
which the rope turns; the _pin_, or axle on which the wheel turns; and
the _strap_, either of rope or iron, which encircles the whole, and
keeps it in its place. The sheave is generally strengthened by letting
in a piece of iron or brass at the centre, called a _bush_.
A MORTICED BLOCK is made of a single block of wood, morticed out to
receive a sheave.
All blocks are single, double, or three-fold, according to the number
of sheaves in them.
There are some blocks that have no sheaves; as follows: a _bull's-eye_,
which is a wooden thimble without a sheave, having a hole through the
centre and a groove round it; and a _dead-eye_, which is a solid block
of wood made in a circular form, with a groove round it, and three
holes bored through it, for the lanyards to reeve through.
A SISTER-BLOCK is formed of one solid piece of wood, with two sheaves,
one above the other, and between the sheaves a score for the middle
seizing. These are oftener without sheaves than with.
SNATCH-BLOCKS are single blocks, with a notch cut in one cheek, just
below the sheave, so as to receive the bight of a fall, without the
trouble of reeving and unreeving the whole. They are generally
iron-bound, and have a hook at one end.
A TAIL-BLOCK is a single block, strapped with an eye-splice, and having
a long end left, by which to make the block fast temporarily to the
rigging. This tail is usually selvageed, or else the strands are opened
and laid up into sennit, as for a gasket.
A TACKLE is a purchase formed by reeving a rope through two or more
blocks, for the purpose of hoisting.
A WHIP is the smallest purchase, and is made by a rope rove through one
single block.
A GUN-TACKLE PURCHASE is a rope rove through two single blocks and made
fast to the strap of the upper block. The parts of all tackles between
the fasts and a sheave, are called the _standing parts_; the parts
between sheaves are called _running parts_; and the part upon which you
take hold in hoisting is called the _fall_.
A WHIP-UPON-WHIP is where the block of one whip is made fast to the
fall of another.
A LUFF-TACKLE PURCHASE is a single and a double block; the end of the
rope being fast to the upper part of the single block, and the fall
coming from the double block. A luff-tackle upon the fall of another
luff-tackle is called _luff-upon-luff_.
A WATCH-TACKLE or TAIL-TACKLE is a luff-tackle purchase, with a hook in
the end of the single block, and a tail to the upper end of the double
block. One of these purchases, with a short fall, is kept on deck, at
hand, in merchant vessels, and is used to clap upon standing and
running rigging, and to get a strain upon ropes.
A RUNNER-TACKLE is a luff applied to a runner, which is a single rope
rove through a single block, hooked to a thimble in the eye of a
pennant.
A SINGLE BURTON is composed of two single blocks, with a hook in the
bight of the running part. Reeve the end of your rope through the upper
block, and make it fast to the strap of the fly-block. Then make fast
your hook to the bight of the rope, and reeve the other end through the
fly-block for a fall. The hook is made fast by passing the bight of the
rope through the eye of the hook and over the whole.