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

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            <p type="main">
              <s>
                <pb xlink:href="040/01/374.jpg" pagenum="345[354]"/>
              facility apprehended in the
                <emph type="italics"/>
              Prolomaick
                <emph.end type="italics"/>
              Syſteme.</s>
            </p>
            <p type="main">
              <s>SALV. </s>
              <s>I neither ought, nor can deny any thing that
                <emph type="italics"/>
              Sagredus
                <emph.end type="italics"/>
                <lb/>
              ſhall requeſt: And the delay by me deſired was to no other end,
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              ſave only that I might have time once again to methodize thoſe
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              prefatory points, in my fancy, that ſerve for a large and plain
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              claration of the manner how the forenamed accidents follow, as
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              well in the
                <emph type="italics"/>
              Copernican
                <emph.end type="italics"/>
              poſition, as in the
                <emph type="italics"/>
              Ptolomaick
                <emph.end type="italics"/>
              : nay, with
                <lb/>
                <arrow.to.target n="marg678"/>
                <lb/>
              much greater facility and ſimplicity in that than in this. </s>
              <s>Whence
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              one may manifeſtly conceive that Hypotheſis to be as eaſie to be
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              effected by nature, as difficult to be apprehended by the
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              ſtanding: yet nevertheleſſe, I hope by making uſe of another
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                <arrow.to.target n="marg679"/>
                <lb/>
              kind of explanation, than that uſed by
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              Copernicus,
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              to render
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              wiſe the apprehending of it ſomewhat leſſe obſcure. </s>
              <s>Which
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              that I may do, I will propoſe certain ſuppoſitions of themſelves
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              known and manifeſt, and they ſhall be theſe that follow.</s>
            </p>
            <p type="margin">
              <s>
                <margin.target id="marg678"/>
                <emph type="italics"/>
              The
                <emph.end type="italics"/>
                <lb/>
              can
                <emph type="italics"/>
              Syſteme
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              cult to be
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              ſtood, but eaſie to
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              be effected.
                <emph.end type="italics"/>
              </s>
            </p>
            <p type="margin">
              <s>
                <margin.target id="marg679"/>
                <emph type="italics"/>
              Neceſſary
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              poſitions for the
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              better conceiving
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              of the conſequences
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              of the Earths
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              tion.
                <emph.end type="italics"/>
              </s>
            </p>
            <p type="main">
              <s>Firſt, I ſuppoſe that the Earth is a ſpherical body, turning
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              round upon its own Axis and Poles, and that each point aſſigned
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              in its ſuperficies, deſcribeth the circumference of a circle,
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              er or leſſer, according as the point aſſigned ſhall be neerer or
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              farther from the Poles: And that of theſe circles the greateſt is
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              that which is deſcribed by a point equidiſtant from the ſaid Poles;
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              and all theſe circles are parallel to each other; and
                <emph type="italics"/>
              Parallels
                <emph.end type="italics"/>
              we
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              will call them.</s>
            </p>
            <p type="main">
              <s>Secondly, The Earth being of a Spherical Figure, and of an
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              pacous ſubſtance, it is continually illuminated by the Sun,
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              ding to the half of its ſurface, the other half remaining obſcure,
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              and the boundary that diſtinguiſheth the illuminated part from
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              the dark being a grand circle, we will call that circle the
                <emph type="italics"/>
                <lb/>
              nator of the light.
                <emph.end type="italics"/>
              </s>
            </p>
            <p type="main">
              <s>Thirdly, If the Circle that is terminator of the light ſhould
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              paſſe by the Poles of the Earth, it would cut (being a grand
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              and principal circle) all the parallels into equal parts; but not
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              paſſing by the Poles, it would cut them all in parts unequal,
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              cept only the circle in the middle, which, as being a grand circle
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              will be cut into equal parts.</s>
            </p>
            <p type="main">
              <s>Fourthly, The Earth turning round upon its own Poles, the
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              quantities of dayes and nights are termined by the arches of the
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              Parallels, interſected by the circle, that is, the terminator of the
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              light, and the arch that is ſcituate in the illuminated Hemiſphere
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              preſcribeth the length of the day, and the remainer is the
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              tity of the night.</s>
            </p>
            <p type="main">
              <s>Theſe things being preſuppoſed, for the more clear
                <lb/>
                <arrow.to.target n="marg680"/>
                <lb/>
              ſtanding of that which remaines to be ſaid, we will lay it down
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              in a Figure. </s>
              <s>And firſt, we will draw the circumference of a
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              circle, that ſhall repreſent unto us that of the grand Orb </s>
            </p>
          </chap>
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