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

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1Body all at once, which would not have been moved by the ſame
Force, in the ſame Time, with an equall Motion, ſave onely in
pieces, without the help of the Leaver.
If of Iron, it is
called a Crow,
if of wood, a Bar
or Hand-ſpike.
Or Space.
Of the CAPSTEN and of the CRANE.
The Inſtruments which we are now about to declare, have
immediate dependence upon the Leaver, nay, are no other
but a perpetual Vectis or Leaver.
For if we ſhall ſuppoſe the
Leaver B A C to be ſuſtained in
the point A, and the Weight G to

hang at the point B, the Force be­
ing placed in C; It is manifeſt,
that transferring the Leaver unto
the points D A E, the Weight G
doth alter according to the Di­
ſtance B D, but cannot much far­
ther continue to raiſe it, ſo that
if it were required to elevate it yet
higher, it would be neceſſary to
ſtay it by ſome other Fulciment
in this Poſition, and to remit or return the Leaver to its former Po­
ſition B A C, and ſuſpending the Weight anew thereat, to raiſe it
once again to the like height B D; and in this manner repeating
the work, many times one ſhall come with an interrupted Motion
to effect the drawing up of the Weight, which for many reſpects
will not prove very beneficial: whereupon this difficulty hath bin
thought on, and remedied, by finding out a way how to unite to­
gether almoſt infinite Leavers, perpetuating the operation without
any interruption; and this hath been done by framing a Wheel
about the Center A, according to the Semidiameter A C, and an
Axis or Nave, about the ſame Center, of which let the Line A B
be the Semidiameter; and all this of very tough wood, or of other
ſtrong and ſolid matter, afterwards ſuſtaining the whole Machine
upon a Gudgeon or Pin of Iron planted in the point A, which
paſſeth quite thorow, where it is held faſt by two fixed Fulciments,
and the Rope D B G, at which the weight G hangeth, being be-laid
or wound about the Axis or Barrell, and applying another Rope
about the greater Wheel, at which let the other Grave I be hang­
ed: It is manifeſt, that the length C A having to the other A B
the ſelf-ſame proportion that the Weight G hath to the Weight I,
it may ſuſtain the Grave G, and with any little Moment more ſhall
move it: and becauſe the Axis turning round together with the
Wheel, the Ropes that ſuſtain the Weights are alwaies pendent and
contingent with the extream Circumferences of that Wheel and