K.
round the second range of pulleys from the inner to the outer side, they are carried to the
second range of pulleys of the higher (trochlea), which passing over, they return to the
lowest: from the lowest they are carried to the upper; and passing round the uppermost (pulleys),
return to the bottom of the machine.
At the root of the machine is placed a third trochlea (P), which is called by the Greeks
ebagonta; by us, artemon. This trochlea is bound to the foot of the machine, and has three
pulleys, around which the ropes passing, are conveyed thence to the men (R) who are to pull
them; and so by the power of three rows of men, the weight is, without a capstan, quickly
taised to the top. This kind of machine is called polyspaston, because it has many pulleys,
which produce facility and expedition. The using of one beam has this convenience, that the
load may be put as much as you will either before or declining to the right or left side.
All the machines before described, are adapted not only to these purposes, but allo to the
loading and unloading of ships; some being disposed erect, others horizontally in verlatile
carchesia; so likewise, without erecting beams, by a similar management of ropes and
trochleas on the plain ground, ships are drawn alhore.
(a*) Our workmen also sometimes make use of a ma¬
chine similar to this, being a long beam fixed at the bottom
in a wheel, as its base; and having sheaves of pulleys at
the top, by which stones or timbers are raised to the height
of the work.
As Perrault's figures of these machines appear to be
accurate and intelligibly drawn, I have made use of them
so far as they accord with my ideas, altering them only
where I imagined they were misconceived or erroneous.
(4*) Vitruvius speaks of the charchesum, at the lalt
chapter of this book, as being a very simple machine, and
usually made by the soldiers themselves. Some part at
the top of a ship's mast was called by the same appella¬
tion, as was also a particular kind of cup. It is supposed
to have been an upright beam, with another lying hori-¬
zontally acros the top, and moveable upon a hinge up¬
ward and downward, as well as having a horizontal
motion around; by these motions therefore it could raile
things from the ground, and then convey them to their
intended situation.
The French grue is a machine of this kind, and is very
serviceable in building, but is not used in this country.
It may not therefore be useless to describe it, and give à
representation thereof. AB, Fig. LXXVII. is a post lup¬
ported by the struts and frame C; on the pivot Areits à
long beam DD, fixed to the timbers EE and FF, and
supported from them obliquely by braces GG. In the
timbers EE and FF (each of which consists of two
pieces bolted together laterally) are cut round holes at
HH, large enough to admit the post AB, which is cut
cylindrically in those places: by these means the whole
triangular frame FDF rests, and may be turned upon the
pivot A, and is preserved in its position by the timbers EE
and FF, embracing the post at HH. From the timber FF
hangs a cylindric wheel I, large and broad enough for two
or three men to walk in it: around the axis K of which
is wound a rope, which passing through the timber FF to
a pulley at the end of the timber E, is carried to the upper
end of the long beam DD; where passing round a
pulley D, it descends, and is fastened to the weight L to
be raised. The men then, by walking in the wheel l,
turn it, and wind the rope round the axis K, thereby
raising the weight; which, when arrived at the height re¬
quired, is, by turning the machine on the pivot 4, con¬
veyed to its place in the work.
Perault has, in his trandlation of Vitruvius, given an
acount of a machine to raise weights, that adts upon the
principle of the roler, having (as he mistakingly asserts)
no friction: a model of it is kept in the cabinet of the
King of France. It consists of a long column 4B,
Fig. LXXVIII. resting at bottom on a pivot A, and lup¬