Galilei, Galileo, Mechanics, 1665

List of thumbnails

< >
11
11 		12
12
13
13 		14
14
15
15 		16
16
17
17 		18
18
19
19 		20
20
< >
page |< < of 40 > >|
    <archimedes>
      <text>
        <body>
          <chap>
            <p type="main">
              <s>
                <pb xlink:href="070/01/016.jpg" pagenum="286"/>
              than the Diſtance A C; that is, as the Force is leſſe than the
                <lb/>
              Weight.</s>
            </p>
            <p type="main">
              <s>Theſe Principles being declared, we will paſſe to the Contem­
                <lb/>
              plation of Pullies, the compoſition and ſtructure of which, together
                <lb/>
              with their uſe, ſhall be deſcribed by us. </s>
              <s>And firſt let us ſuppoſe the
                <lb/>
                <arrow.to.target n="marg1109"/>
                <lb/>
              ^{*} Little Pulley A B C, made of Mettall or hard Wood, voluble a­
                <lb/>
              bout it's Axis which paſſeth thorow it's Center D, and about this
                <lb/>
                <figure id="id.070.01.016.1.jpg" xlink:href="070/01/016/1.jpg" number="11"/>
                <lb/>
              Pulley let the Rope E A B C be put,
                <lb/>
              at one end of whichlet the Weight E
                <lb/>
              hang, and at the other let us ſuppoſe
                <lb/>
              the Force F. </s>
              <s>I ſay, that the Weight
                <lb/>
              being ſuſtained by a Force equall to
                <lb/>
              it ſelf in the upper Nut or Pulley
                <lb/>
              A B C, bringeth ſome benefit, as the
                <lb/>
              moving or ſuſtaining of the ſaid
                <lb/>
              Weight with the Force placed in F:
                <lb/>
              For if we ſhall underſtand, that from
                <lb/>
              the Center D, which is the place of the Fulciment, two Lines be
                <lb/>
              drawn out as far as the Circumference of the Pulley in the points
                <lb/>
              A and C, in which the pendent Cords touch the Circumference, we
                <lb/>
              ſhall have a Ballance of equal Arms which determine the Diſtance
                <lb/>
              of the two Suſpenſions from the Center and Fulciment D: Where­
                <lb/>
              upon it is manifeſt, that the Weight hanging at A cannot be ſuſtain­
                <lb/>
              ed by a leſſer Weight hanging at G, but by one equal to it; ſuch
                <lb/>
              is the nature of equal Weights hanging at equal Diſtances. </s>
              <s>And
                <lb/>
              although in moving downwards, the Force F cometh to turn about
                <lb/>
              the Pulley A B C, yet there followeth no alteration of the Alti­
                <lb/>
              tude or Reſpect, that the Weight and Force have unto the two
                <lb/>
              Diſtances A D and D C, nay, the Pulley encompaſſed becometh a
                <lb/>
              Ballance equal to A C, but perpetuall. </s>
              <s>Whence we may learn,
                <lb/>
              how childiſhly
                <emph type="italics"/>
              Ariſtotle
                <emph.end type="italics"/>
              deceiveth himſelf, who holds, that by making
                <lb/>
              the ſmall Pulley A B C bigger, one might draw up the Weight with
                <lb/>
              a leſſer Force; he conſidering that upon the enlargement of the
                <lb/>
              ſaid Pulley, the Diſtance D C encreaſed, but not conſidering that
                <lb/>
              there was as great an encreaſe of the other Diſtance of the Weight,
                <lb/>
              that is, the other Semidiameter D A. </s>
              <s>The benefit therefore that may
                <lb/>
              be drawn from the Inſtrument above ſaid, is nothing at all as to the
                <lb/>
              diminution of the labour: and if any one ſhould ask how it hap­
                <lb/>
              pens, that on many occaſions of raiſing Weights, this means is made
                <lb/>
              uſe of to help the Axis, as we ſee, for example, in drawing up the
                <lb/>
              Water of Wells; it is anſwered, that that is done, becauſe that
                <lb/>
              by this means the manner of employing the Force is found more
                <lb/>
              commodious: for being to pull downwards, the proper Gravity of
                <lb/>
              our Arms and other parts help us, whereas if we were to draw
                <lb/>
              the fame Weight upwards with a meer Rope, by the ſole ſtrength </s>
            </p>
          </chap>
        </body>
      </text>
    </archimedes>
Impressum