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

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              <s>
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              poſite blank, if the ſight were made in one onely point; but if we
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              ſhould find, that the edges of the white cartel appear diſcovered,
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              it ſhall be a neceſſary argument that the viſual rayes do not iſſue
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              from one ſole point. </s>
              <s>And to make the white label to be hid by
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              the black, it will be requiſite to draw neerer with the eye:
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              Therefore, having approached ſo neer, that the intermediate
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              bel covereth the other, and noted how much the required
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              proximation was, the quantity of that approach ſhall be the
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              tain meaſure, how much the true concourſe of the viſive rayes, is
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              remote from the eye in the ſaid operation, and we ſhall moreover
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              have the diameter of the pupil, or of that circlet from whence
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              the viſive rayes proceed: for it ſhall be to the breadth of the
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              black paper, as is the diſtance from the concourſe of the lines,
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              that are produced by the edges of the papers to the place where
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              the eye ſtandeth, when it firſt ſeeth the remote paper to be hid
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              by the intermediate one, as that diſtance is, I ſay, to the diſtance
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              that is between thoſe two papers. </s>
              <s>And therefore when we
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              would, with exactneſſe, meaſure the apparent diameter of a Star,
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              having made the obſervation in manner, as aforeſaid, it would be
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              neceſſary to compare the diameter of the rope to the diameter of
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              the pupil; and having found
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              v.g.
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              the diameter of the rope to be
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              quadruple to that of the pupil, and the diſtance of the eye from
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              the rope to be, for example, thirty yards, we would ſay, that the
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              true concourſe of the lines produced from the ends or
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              ties of the diameter of the ſtar, by the extremities of the
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              meter of the rope, doth fall out to be fourty yards remote from
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              the ſaid rope, for ſo we ſhall have obſerved, as we ought, the
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              portion between the diſtance of the rope from the concourſe of
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              the ſaid lines, and the diſtance from the ſaid concourſe to the
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              place of the eye, which ought to be the ſame that is between
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              the diameter of the rope, and diameter of the pupil.</s>
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              * Striſce.
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                <emph type="italics"/>
              How to find the
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              diſtance of the rays
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              concourſe from the
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              pupil.
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              </s>
            </p>
            <p type="main">
              <s>SAGR. </s>
              <s>I have perfectly underſtood the whole buſineſſe, and
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              therefore let us hear what
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              Simplicius
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              hath to alledge in defence of
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              the
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              Anti-Copernicans.
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              </s>
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            <p type="main">
              <s>SIMP. </s>
              <s>Albeit that grand and altogether incredible
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              nience inſiſted upon by theſe adverſaries of
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              Copernicus
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              be much
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              moderated and abated by the diſcourſe of
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              Salviatus,
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              yet do I
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              not think it weakened ſo, as that it hath not ſtrength enough left
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              to foil this ſame opinion. </s>
              <s>For, if I have rightly apprehended the
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              chief and ultimate concluſion, in caſe, the ſtars of the ſixth
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              nitude were ſuppoſed to be as big as the Sun, (which yet I can
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              hardly think) yet it would ſtill be true, that the grand Orb [or
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              Ecliptick] would occaſion a mutation and variation in the ſtarry
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              Sphere, like to that which the ſemidiameter of the Earth
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              ceth in the Sun, which yet is obſervable; ſo that neither that, no </s>
            </p>
          </chap>
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