Salusbury, Thomas, Mathematical collections and translations (Tome I), 1667

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1
From the Inſtrument laſt deſcribed, the other Inſtrument which
we
call the Crane is not much different, as to form, nay, differeth
nothing
, ſave in the way of applying or employing it: For that the
Capſten
moveth and is conſtituted perpendicular to the Horizon,
and
the Crane worketh with its Moment parallel to the ſame Ho­
187[Figure 187]
rizon
.
For if upon the Circle D A E we ſuppoſe an Axis to be
placed
Column-wiſe, turning about the Center B, and about which
the
Rope D H, faſtened to the Weight that is to be drawn, is be­
laid
, and if the Bar F E B D be let into the ſaid Axis [by the Mor­
tace
B] and the Force of a Man, of an Horſe, or of ſome other
Animal
apt to draw, be applyed at its end F, which moving round,
paſſeth
along the Circumference F G C, the Crane ſhall be framed
and
finiſhed, ſo that by carrying round the Bar F B D, the Barrell
or
Axis E A D ſhall turn about, and the Rope which is twined
bout
it, ſhall conſtrain the Weight H to go forward: And becauſe
the
point of the Fulciment about which the Motion is made, is the
point
B, and the Moment keeps at a Diſtance from it according to
the
Line B F, and the Reſiſtor at the Diſtance B D, the Leaver
F
B D is formed, by vertue of which the Force acquireth Moment
equall
to the Reſiſtance, if ſo be, that it be in proportion to it, as
the
Line B D is to B F, that is, as the Semidiameter of the Axis to
the
Semidiameter of the Circle, along whoſe Circumference the
Force
moveth.
And both in this, and in the other Inſtrument we
are
to obſerve that which hath been frequently mentioned, that is,
That
the benefit which is derived from theſe Machines, is not that
which
the generality of the Vulgar promiſe themſelves from the
Mechanicks
; namely, that being too hard for Nature, its poſſible

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