Galilei, Galileo, Mechanics, 1665

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1the ſaid Cylinder the Helical Line deſcribed by the Line AEFGH,
which
we vulgarly call the Wale of the Screw, which was produ­
ced
by the Line A C.
And in this manner is the Inſtrument made,
which
is by the Greeks called Κόχλος, and by us a Screw; which

winding
about
cometh
to work
24[Figure 24]
and
inſinu­
ate
with its
Wales
under
the
Weight, and
with
facility rai­
ſeth
it.
And we
having
demon­
ſtrated
, That up­
on
[or along]
the
elevated Plane the Force hath the ſame proportion to the
Weight
, that the perpendicular Altitude of the ſaid Plane hath to
its
Length; ſo, ſuppoſing that the Force in the Screw A B C D is
multiplied
according to the proportion by which the Length of the
whole
Wale exceedeth the Altitude C B, from hence we come
to
know that making the Screw with its Helix's more thick or cloſe
together
, it becometh ſo much the more forceable, as being begot
by
a Plane leſs elevated, and whoſe Length regards its own Per­
pendicular
Altitude with greater proportion.
But we will not
omit
to advertiſe you, that deſiring to find the Force of a propo­
ſed
Screw, it will not be needful that we meaſure the Length of
all
its Wales, and the Altitude of the whole Cylinder, but it
will
be enough if we ſhall but examine how many times the Di­
ſtance
betwixt two ſingle and Contiguous terms do enter into one
ſole
Turn of the ſame Wale, as for example, how many times
the
Diſtance AF is contained in the Length of the Turn AEF:
For
this is the ſame proportion that the Altitude CB hath to all
the
Wale.
Levar in capo
ſignfieth to lift
on
high by force

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