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

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            <p type="main">
              <s>
                <pb xlink:href="040/01/325.jpg" pagenum="305"/>
              the ſaid irradiation of four inches to a circle that hath but two
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              ches of diameter onely, the diameter of the irradiation or
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              land would be ten inches, and the ſuperficial content of the circle
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              would be to the
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              area
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              of the naked body, as 100. to 4. for thoſe
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              are the ſquares of 10. and of 2. the agrandizement would
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              fore be 25. times ſo much; and laſtly, the four inches of hair or
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              fringe, added to a ſmall circle of an inch in diameter, the ſame
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              would be increaſed 81. times; and ſo continually the
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              tions are made with a proportion greater and greater, according
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              as the real objects that increaſe, are leſſer and leſſer.</s>
            </p>
            <p type="margin">
              <s>
                <margin.target id="marg554"/>
                <emph type="italics"/>
              Superficial
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              gures encreaſing
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              proportion double to
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              their lines.
                <emph.end type="italics"/>
              </s>
            </p>
            <p type="main">
              <s>SAGR. </s>
              <s>The doubt which puzzled
                <emph type="italics"/>
              Simplicius
                <emph.end type="italics"/>
              never troubled
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              me, but certain other things indeed there are, of which I deſire
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              a more diſtinct underſtanding; and in particular, I would know
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              on what ground you affirm that the ſaid agrandizement is alwayes
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              equal in all viſible
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                <arrow.to.target n="marg555"/>
              </s>
            </p>
            <p type="margin">
              <s>
                <margin.target id="marg555"/>
                <emph type="italics"/>
              Objects the more
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              vigorous they are
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              in light, the more
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              they do ſeem to
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              creaſe.
                <emph.end type="italics"/>
              </s>
            </p>
            <p type="main">
              <s>SALV. </s>
              <s>I have already declared the ſame in part, when I ſaid,
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              that onely lucid objects ſo increaſed, and not the obſcure; now I
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              adde what remaines, that of the reſplendent objects thoſe that are
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              of a more bright light, make the reflection greater and more
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              ſplendent upon our pupil; whereupon they ſeem to augment
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              much more than the leſſe lucid: and that I may no more inlarge
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              my ſelf upon this particular, come we to that which the true
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              ſtris of
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              Astronomy,
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              Experience, teacheth us. </s>
              <s>Let us this evening,
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              when the air is very obſcure, obſerve the ſtar of
                <emph type="italics"/>
              Jupiter
                <emph.end type="italics"/>
              ; we
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              ſhall ſee it very glittering, and very great; let us afterwards look </s>
            </p>
            <p type="main">
              <s>
                <arrow.to.target n="marg556"/>
                <lb/>
              through a tube, or elſe through a ſmall trunk, which clutching the
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              hand cloſe, and accoſting it to the eye, we lean between the palm
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              of the hands and the fingers, or elſe by an hole made with a ſmall
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              needle in a paper; and we ſhall ſee the ſaid ſtar diveſted of its
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              beams, but ſo ſmall, that we ſhall judge it leſſe, even than a
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              eth part of its great glittering light ſeen with the eye at liberty:
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              we may afterwards behold the
                <emph type="italics"/>
              Dog-ſtars
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              beautiful and bigger than
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                <arrow.to.target n="marg557"/>
                <lb/>
              any of the other fixed ſtars, which ſeemeth to the bare eye no
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              great matter leſſe than
                <emph type="italics"/>
              Jupiter
                <emph.end type="italics"/>
              ; but taking from it, as before, the
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              irradiation, its
                <emph type="italics"/>
              Diſcus
                <emph.end type="italics"/>
              will ſhew ſo little, that it will not be
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              thought the twentieth part of that of
                <emph type="italics"/>
              Jupiter,
                <emph.end type="italics"/>
              nay, he that hath not
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              very good eyes, will very hardly diſcern it; from whence it may
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              be rationally inferred, that the ſaid ſtar, as having a much more
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              lively light than
                <emph type="italics"/>
              Jupiter,
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              maketh its irradiation greater than
                <emph type="italics"/>
                <lb/>
              ter
                <emph.end type="italics"/>
              doth his. </s>
              <s>In the next place, as to the irradiation of the Sun
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              and Moon, it is as nothing, by means of their magnitude, which
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                <arrow.to.target n="marg558"/>
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              poſſeſſeth of it ſelf alone ſo great a ſpace in our eye, that it
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              veth no place for the adventitious rayes; ſo that their faces ſeem
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              cloſe clipt, and terminate. </s>
              <s>We may aſſure our ſelves of the ſame
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              truth by another experiment which I have often made triall of; </s>
            </p>
          </chap>
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