Barrow, Isaac, Lectiones opticae & geometricae : in quibus phaenomenon opticorum genuinae rationes investigantur, ac exponuntur: et generalia curvarum linearum symptomata declarantur

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            <s xml:id="echoid-s3225" xml:space="preserve">
              <pb o="57" file="0075" n="75" rhead=""/>
            è dictis colligatur licet, quòd oculo, cujus Centrum O uſpiam in
              <lb/>
            ipſa N Π ponitur, circa punctum Z (ipſam N Π prænotato modo
              <lb/>
            quadriſecans) radiantis imago conſpicietur. </s>
            <s xml:id="echoid-s3226" xml:space="preserve">Sit enim pupillæ (prout
              <lb/>
            antehac aliquoties) diameter EF; </s>
            <s xml:id="echoid-s3227" xml:space="preserve">per eujuſce terminos tranſeant
              <lb/>
            radiorum LM, RS reflexi LE, RF; </s>
            <s xml:id="echoid-s3228" xml:space="preserve">quorum iſte ſecet ipſum N Π in
              <lb/>
            Y, hic in X. </s>
            <s xml:id="echoid-s3229" xml:space="preserve">quoniam igitur radiorum obliquiorum ipſo RS,
              <lb/>
            rectiorum ipſo LM nullus oculum intrabit; </s>
            <s xml:id="echoid-s3230" xml:space="preserve">utì ſuprà non ſemel argu-
              <lb/>
            mentati ſumus, intra ſpatium XY neceſſario conſiſtet imago. </s>
            <s xml:id="echoid-s3231" xml:space="preserve">quineti-
              <lb/>
              <note position="right" xlink:label="note-0075-01" xlink:href="note-0075-01a" xml:space="preserve">Fig. 78.</note>
            am cùm radiorum arcui LR incidentium qui prope punctum Z re-
              <lb/>
            flectuntur axi N Π propiùs adjacentes perpendicularius oculum fe-
              <lb/>
            riunt, ìdque ſpiſſiùs (ut ex analogia par eſt exiſtimare; </s>
            <s xml:id="echoid-s3232" xml:space="preserve">nec enim
              <lb/>
            id operoſiùs aggrediar demonſtrare) propter aliquoties expoſitas
              <lb/>
            cauſas ab eo videbuntur obtutum afficientes radii promanare; </s>
            <s xml:id="echoid-s3233" xml:space="preserve">hoc eſt
              <lb/>
            ad ipſum imago conſiſtet. </s>
            <s xml:id="echoid-s3234" xml:space="preserve">Accedit quod ob anguſtiam pupillæ ſpa-
              <lb/>
            tium XY ſatìs modicum exiſtit; </s>
            <s xml:id="echoid-s3235" xml:space="preserve">ut puncti modum vix excedere vi-
              <lb/>
            deatur.</s>
            <s xml:id="echoid-s3236" xml:space="preserve"/>
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          <p>
            <s xml:id="echoid-s3237" xml:space="preserve">XIX. </s>
            <s xml:id="echoid-s3238" xml:space="preserve">Subdo; </s>
            <s xml:id="echoid-s3239" xml:space="preserve">ſi ſtatuatur oculi centrum uſpiam in ZN; </s>
            <s xml:id="echoid-s3240" xml:space="preserve">iſque ver-
              <lb/>
            ſus partes N obvertatur; </s>
            <s xml:id="echoid-s3241" xml:space="preserve">objectum confuſiùs apparere; </s>
            <s xml:id="echoid-s3242" xml:space="preserve">quippe cùm
              <lb/>
            reflexi viſum convergentes appellant; </s>
            <s xml:id="echoid-s3243" xml:space="preserve">vel quoniam imago Z tunc pone
              <lb/>
            viſum conſiſtit.</s>
            <s xml:id="echoid-s3244" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s3245" xml:space="preserve">XX. </s>
            <s xml:id="echoid-s3246" xml:space="preserve">Hinc à ſpeculo Cavo tantùm una repræſentatur Imago, ſaltem
              <lb/>
            bene diſtincta. </s>
            <s xml:id="echoid-s3247" xml:space="preserve">Nam in duorum reflexorum N Π;</s>
            <s xml:id="echoid-s3248" xml:space="preserve">, R σ concurſu X
              <lb/>
            ſtatuatur oculi centrum; </s>
            <s xml:id="echoid-s3249" xml:space="preserve">& </s>
            <s xml:id="echoid-s3250" xml:space="preserve">ſit R ζ = 1/4 R σ; </s>
            <s xml:id="echoid-s3251" xml:space="preserve">unde R ζ &</s>
            <s xml:id="echoid-s3252" xml:space="preserve">lt; </s>
            <s xml:id="echoid-s3253" xml:space="preserve">RX.
              <lb/>
            </s>
            <s xml:id="echoid-s3254" xml:space="preserve">itaque ſpectabitur quæ ad ζ imago ab oculo in X collocato, verſúſque
              <lb/>
            partes NR obverſo; </s>
            <s xml:id="echoid-s3255" xml:space="preserve">ſed tum imago Z poſt oculum conſiſtit.</s>
            <s xml:id="echoid-s3256" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s3257" xml:space="preserve">XXI. </s>
            <s xml:id="echoid-s3258" xml:space="preserve">Et hæc quidem rectè percepta, ſerióquè perpenſa vix addubi-
              <lb/>
            to quin facilè ſibi fidem conciliatura ſint; </s>
            <s xml:id="echoid-s3259" xml:space="preserve">nihil ut ſit opus adverſantia
              <lb/>
            _ſeu veterum Opticorum decreta, ſeu recentiorum Commenta pluribus_
              <lb/>
            _convellere;_ </s>
            <s xml:id="echoid-s3260" xml:space="preserve">quæ certè cùm nullâ perſpicuâ ratione nituntur, tum ab
              <lb/>
            experientia plerumque diſcordant. </s>
            <s xml:id="echoid-s3261" xml:space="preserve">Cætera verò ſiqua reſtant ad hoc
              <lb/>
            argumentum ſpectantia ſtudio veſtro commendabimus elicienda; </s>
            <s xml:id="echoid-s3262" xml:space="preserve">mox
              <lb/>
            ad è ſenſibiliter finita diſtantia radiantis puncti _Symptomata_ ſimiliter
              <lb/>
            exploranda animum adjecturi.</s>
            <s xml:id="echoid-s3263" xml:space="preserve"/>
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