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

Table of figures

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              <s>
                <pb xlink:href="040/01/1017.jpg" pagenum="323"/>
              Rectangle F H deſcribeth whilſt it draweth the Weight D along
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              the Plane B A, by the means of a Chord parallel to this Plane, and
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              paſſing about the Pulley E, in ſuch ſort, that H G, that is the height
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              of this Rectangle, is equal to B A, along which the Weight D is to
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              move, whilſt it mounteth to the height of the Line C A. </s>
              <s>And N O
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              repreſents the firſt Dimenſion of ſuch another Force, that is de­
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              ſcribed by the Rectan­
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              gle N P, in the time that
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                <figure id="id.040.01.1017.1.jpg" xlink:href="040/01/1017/1.jpg" number="220"/>
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              it is raiſing the Weight
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              L to M. </s>
              <s>And I ſuppoſe
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              that L M is equal to B A,
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              or double to C A; and
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              that N O is to F G, as
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              O P is to G H. </s>
              <s>This
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              done, I conſider that at
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              ſuch time as the Weight
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              D is moved from B to­
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              wards A, one may ima­
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              gine its Motion to be
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              compoſed of two others, of which the one carrieth it from B R to­
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              wards C A, (to which operation there is no Force required, as all
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              thoſe ſuppoſe who treat of the Mechanicks) and the other raiſeth
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              it from B C towards R A, for which alone the Force is required:
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              inſomuch that it needs neither more nor leſs Force to move it
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              along the Inclined Plane B A, than along the Perpendicular C A.
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              </s>
              <s>For I ſuppoſe that the unevenneſſes,
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              &c.
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              of the Plane do not
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              at all hinder it, like as it is alwaies ſuppoſed in treating of this
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              matter.</s>
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              <s>So then the whole Force F H is employed only about the raiſing
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              of D to the height of C A: and foraſmuch as it is exactly equal to
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              the Force N P, that is required for the raiſing of L to the Height
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              of L M, double to C A, I conclude by my Principle that the
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              Weight D is double to the Weight L. </s>
              <s>For in regard that it is
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              neceſſary to employ as much Force for the one as for the other,
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              there is as much to be raiſed in the one as in the other; and no
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              more knowledge is required than to count unto two for the
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              knowing that it is alike facile to raiſe 200 pounds from C to A,
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              as to raiſe 100 pounds from L to M: ſince that L M is double
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              to C A.</s>
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              <s>You tell me, moreover, that I ought more particularly to ex­
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              plain the nature of the Spiral Line that repreſenteth the Plane
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              equally enclined, which hath many qualities that render it ſuffi­
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              ciently knowable.</s>
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