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

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1with a Machine to overcome a Reſiſtance, though great, with a
ſmall Force, in regard, that we ſhall manifeſtly prove that the ſame
Force placed in F, might in the ſame Time conveigh the ſame
Weight, with the ſame Motion, unto the ſame Diſtance, without
any Machine at all: For ſuppoſing, for example, that the Reſiſtance
of the Grave H be ten times greater than the Force placed in F, it

will be requiſite for the mo­
ving of the ſaid Reſiſtance,
that the Line F B be decuple
to B D; and conſequently,
that the Circumference of the
Circle F G C be alſo decuple
to the Circumference E A D:
and becauſe when the Force
ſhall be moved once along the
whole Circumference of the
Circle F G C, the Barrel EAD,
about which the Rope is be-laid which draweth the Weight, ſhall
likewiſe have given one onely turn; it is manifeſt, that the Weight
H ſhall not have been moved more than the tenth part of that way
which the Mover ſhall have gone.
If therefore the Force that is to
move a Reſiſtance that is greater than it ſelf, for ſuch an aſſigned
Space by help of this Machine, muſt of neceſſity move ten times as
far, there is no doubt, but that dividing that Weight into ten parts,
each of them ſhall be equall to the Force, and conſequently, might
have been tranſported one at a Time, as great a Space as that
which it ſelf did move, ſo that making ten journeys, each equal to
the Circumference E A D, it ſhall not have gone any farther than
if it did move but once alone about the Circumference F G C;
and ſhall have conveighed the ſame Weight H to the ſame Di­
ſtance.
The benefit therefore that is to be derived from theſe
Machines is, that they carry all the Weight together, but not with
leſſe Labour, or with greater Expedition, or a greater Way than
the ſame Force might have done conveying it by parcels.
Of PULLIES.
The Inſtruments, whoſe Natures are reducible unto the Bal­
lance, as to their Principle and Foundation, and others little
differing from them, have been already deſcribed; now for
the underſtanding of that which we have to ſay touching Pullies,
it is requiſite, that we conſider in the firſt place another way to uſe
the Leaver, which will conduce much towards the inveſtigation of
the Force of Pullies, and towards the underſtanding of other Me­
chanical Effects.
The uſe of the Leaver above declared ſuppoſed