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

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          <head xml:id="echoid-head14" xml:space="preserve">
            <emph style="sc">Lect</emph>
          . III.</head>
          <p>
            <s xml:id="echoid-s807" xml:space="preserve">I. </s>
            <s xml:id="echoid-s808" xml:space="preserve">HYpotheſes Opticæ primarias, & </s>
            <s xml:id="echoid-s809" xml:space="preserve">fundamentales quaſi leges
              <lb/>
            expoſuimus hactenus, & </s>
            <s xml:id="echoid-s810" xml:space="preserve">excuſſimus quomodocunque: </s>
            <s xml:id="echoid-s811" xml:space="preserve">Se-
              <lb/>
            quitur jam ut ex iis emergentia quædam (ad apparentiarum cauſas tam
              <lb/>
            verè quàm expeditè diſcernendas conducentia) ſubjungamus corollaria;
              <lb/>
            </s>
            <s xml:id="echoid-s812" xml:space="preserve">de cæteris quæ faciliora videntur, aut uſum præ ſe ferunt potiſſimum
              <lb/>
            ſeligentes. </s>
            <s xml:id="echoid-s813" xml:space="preserve">Radios autem jam conſideramus, ut unicâ dimenſione præ-
              <lb/>
            ditos (ſiquidem reliquæ, quibus Phyſicè gaudent, parùm faciunt ad
              <lb/>
            computationes hîc inſtitutas) ut lineas, inquam ceu vulgò fit, rectas
              <lb/>
            concipimus a lucido quolibet aut aſpectabili puncto dimanantes. </s>
            <s xml:id="echoid-s814" xml:space="preserve">Quin
              <lb/>
            & </s>
            <s xml:id="echoid-s815" xml:space="preserve">cum, hoc admiſſo, ſinguli cujuſque radii inflectio in ſuperficie per-
              <lb/>
            agatur ad planum inflectens recta (uti conſtat è præmiſſis) cùm & </s>
            <s xml:id="echoid-s816" xml:space="preserve">no-
              <lb/>
            bis præſertim mox inſtitutum ſit ſingulorum punctorum radiationes
              <lb/>
            conſequentia ſymptomata ſic expendere, ut locos ipſorum apparen-
              <lb/>
            tes determinemus, oculi reſpectu centrum habentis in ejuſmodi
              <lb/>
            plano uſpiam conſtitutum; </s>
            <s xml:id="echoid-s817" xml:space="preserve">pro planis ubique rectas lineas, pro Sphæ-
              <lb/>
            ricis ſuperficiebus peripherias circulares, pro reliquis lineas reſpectivè
              <lb/>
            congruas, brevitati conſulentes & </s>
            <s xml:id="echoid-s818" xml:space="preserve">perſpicuitati, ſubſtituemus. </s>
            <s xml:id="echoid-s819" xml:space="preserve">Porrò
              <lb/>
            cùm quo præciſè modo peragatur viſio, quibúſque prædita ſit affecti-
              <lb/>
            onibus adhuc expoſitum non ſit; </s>
            <s xml:id="echoid-s820" xml:space="preserve">Et de illa tamen ſubindè craſſius ali-
              <lb/>
            quid ac generalius dicendis intexere fortaſſis ex uſu fuerit, illa ſaltem
              <lb/>
            pervnlgata, poſt hac curioſiùs expendenda, jam προλεπτικῶς adſume-
              <lb/>
            mus; </s>
            <s xml:id="echoid-s821" xml:space="preserve">nempe: </s>
            <s xml:id="echoid-s822" xml:space="preserve">Viſibile punctum in illo radio ſitum apparere, qui pro-
              <lb/>
            cedens ab ipſo (directè vel inflexè) centrum oculi permeat; </s>
            <s xml:id="echoid-s823" xml:space="preserve">proindéq; </s>
            <s xml:id="echoid-s824" xml:space="preserve">
              <lb/>
            ſitum objectorum è radiorum ità tranſeuntium poſitione judicari. </s>
            <s xml:id="echoid-s825" xml:space="preserve">Ma-
              <lb/>
            jora, minora, vel æqualia videri objecta, prout ipſorum extrema pun-
              <lb/>
            cta radiis cernuntur angulos ad oculi centrum reſpectivè majores, mi-
              <lb/>
            nores, aut æquales conſtituentibus; </s>
            <s xml:id="echoid-s826" xml:space="preserve">diſtinctam unius cujuſque puncti
              <lb/>
            viſionem radiis effici modo naturali, hoc eſt, divergentèr, oculo illa-
              <lb/>
            bentibus; </s>
            <s xml:id="echoid-s827" xml:space="preserve">Et ſiqua ſunt his agnata pariter obvia, ſeu manifeſta. </s>
            <s xml:id="echoid-s828" xml:space="preserve">
              <lb/>
            Quinetiam, verborum parci, vocabulis paſſim receptis & </s>
            <s xml:id="echoid-s829" xml:space="preserve">uſitatis defi-
              <lb/>
            niendis aut explicandis abſtinentes, ipſorum ſupponimus </s>
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