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directions. Under the place where the guy ropes at ton
are made fast to the pole, two cheeks are fixed, above
which the block is tied with ropes. Under the block a
pièce of timber about two feet long, six inches wide, and
four inches thick, is placed. The blocks have thre
ranks of pulleys latitudinally, so that it is necessary to
conduct three leading ropes from the upper part of the
machine; these are brought down to the lower block.
and are passed through its upper pulleys from the side
next the pole. They then are carried to the upper block.
passing from the outer sides of the lower pulleys to the
inner sides of the lower pulleys of the upper block.
Descending once more to the inferior block, they pass
round the second rank of pulleys from the inner to the
outer side, and are then returned to the second rank of
pulleys in the higher block, over which they pass and re
turn to the lowest, whence they are again carried up-
wards, and passing round the uppermost pulley, return
to the lower part of the machine. A third block is fixed
near the bottom of the pole, whose Greek name is
crayo, but with us it is called Artemo. This block,
which is made fast to the pole at a small distance from
the ground, has three pulleys through which the ropes
are passed, for the men to work them. Thus, three sets
of men, working without the intervention of a capstan,
quickly raise the weight to its required height. This
species of machine is called Polyspaston, because the
facility and despatch in working it, is obtained by means
of many pulleys. One convenience in using a single
pole is, that the situation of the weight in relation to the
pole, whether before it or to the right or left of it, is of
no consequence. All the machines above described, are
not only adapted to the purposes mentioned, but are also
useful in loading and unloading ships, some upright,
others horizontal, with a rotatory motion. On the ground,
however, without the aid of the poles, ships are drawn
on shore by the mere application of blocks and ropes.
