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-s682" xml:space="preserve">
              <pb o="18" file="0036" n="36" rhead=""/>
            reflectionis leges examuſſim obſervat. </s>
            <s xml:id="echoid-s683" xml:space="preserve">Nam quoniam iſoſcelis trian-
              <lb/>
            guli ZB β anguli ZB β Z β B ſunt æquales, etiam anguli (de rectis
              <lb/>
            reſidui) ABE, α β F pares erunt; </s>
            <s xml:id="echoid-s684" xml:space="preserve">quod reflectioni proprium eſt.
              <lb/>
            </s>
            <s xml:id="echoid-s685" xml:space="preserve">Itaque non abs recto pronunciant hoc Dioptrici; </s>
            <s xml:id="echoid-s686" xml:space="preserve">neque tamen cauſam,
              <lb/>
              <note position="left" xlink:label="note-0036-01" xlink:href="note-0036-01a" xml:space="preserve">_Kepl. prop. 14_.</note>
            fortaſſis ab iis prætermiſſam, tacere volui, nonnihil ab immediatæ re-
              <lb/>
            flectionis cauſa diverſam; </s>
            <s xml:id="echoid-s687" xml:space="preserve">nè quiſquam hæſitet, aut hoc adſumenti
              <lb/>
            gravetur concedere.</s>
            <s xml:id="echoid-s688" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s689" xml:space="preserve">VII. </s>
            <s xml:id="echoid-s690" xml:space="preserve">Hæc autem doctrina cùm multis experimentis utcunque com-
              <lb/>
            probari queat, unum ſaltem breviter attingam ſatìs illuſtre, neminíſq;
              <lb/>
            </s>
            <s xml:id="echoid-s691" xml:space="preserve">non examini patens. </s>
            <s xml:id="echoid-s692" xml:space="preserve">Eſto triangulum ABC ſectio priſmatis triangu-
              <lb/>
            laris æquilateri (nimirum vitrei, ſeu cryſtallini) baſi parallela; </s>
            <s xml:id="echoid-s693" xml:space="preserve">in hu-
              <lb/>
              <note position="left" xlink:label="note-0036-02" xlink:href="note-0036-02a" xml:space="preserve">Fig. 13.</note>
            jus autem baſe ſumatur punctum quodpiam F, & </s>
            <s xml:id="echoid-s694" xml:space="preserve">ſit angulus CFG
              <lb/>
            circiter graduum 50. </s>
            <s xml:id="echoid-s695" xml:space="preserve">(unde juxta doctrinam hîc inſinuatam, & </s>
            <s xml:id="echoid-s696" xml:space="preserve">poſteà
              <lb/>
            clariùs exprimendam, radius GF velut extremus erit eorum, qui re-
              <lb/>
            ctæ BC è vitri partibus illabentes refractionem patientur; </s>
            <s xml:id="echoid-s697" xml:space="preserve">eo ſcilicet
              <lb/>
            obliquior quilibet reflectetur.) </s>
            <s xml:id="echoid-s698" xml:space="preserve">Sit igitur (quoniam utramque quaſi
              <lb/>
            patitur inflectionem) ejus refractus FM, reflexus FE; </s>
            <s xml:id="echoid-s699" xml:space="preserve">item FGre-
              <lb/>
            fringatur in GO, & </s>
            <s xml:id="echoid-s700" xml:space="preserve">FE in ER. </s>
            <s xml:id="echoid-s701" xml:space="preserve">Porrò jam in GO ſtatuatur oculi
              <lb/>
            centrum O; </s>
            <s xml:id="echoid-s702" xml:space="preserve">& </s>
            <s xml:id="echoid-s703" xml:space="preserve">ab eo prodeat radius OQ, qui refringatur in QP;
              <lb/>
            </s>
            <s xml:id="echoid-s704" xml:space="preserve">ipſorum OG, OQ refracti GF, OP (uti ſecundum principia no-
              <lb/>
            ſtra poſthac conſtabit) progredientes divergent; </s>
            <s xml:id="echoid-s705" xml:space="preserve">erítque proptereà
              <lb/>
            ang. </s>
            <s xml:id="echoid-s706" xml:space="preserve">QPC &</s>
            <s xml:id="echoid-s707" xml:space="preserve">gt; </s>
            <s xml:id="echoid-s708" xml:space="preserve">GFC; </s>
            <s xml:id="echoid-s709" xml:space="preserve">quare radius QP medium BC penetrabit,
              <lb/>
            ac refringetur, puta in PN; </s>
            <s xml:id="echoid-s710" xml:space="preserve">liquebit autem è dicendis refractos FM,
              <lb/>
            PN à ſe divergere; </s>
            <s xml:id="echoid-s711" xml:space="preserve">Hinc jam radiis MF, NP interpoſitum objectum
              <lb/>
            radiis OG, OQ interjectum apparebit, velut ad μ ν, ſitu neutiquam
              <lb/>
            immutatum. </s>
            <s xml:id="echoid-s712" xml:space="preserve">Rurſus autem ab oculi dicto centro prodeat alter radius
              <lb/>
            OK, cujus refractus ſit KI; </s>
            <s xml:id="echoid-s713" xml:space="preserve">hìc itaque rurſum à GF diverget, ac
              <lb/>
            indè erit ang. </s>
            <s xml:id="echoid-s714" xml:space="preserve">KIF &</s>
            <s xml:id="echoid-s715" xml:space="preserve">lt; </s>
            <s xml:id="echoid-s716" xml:space="preserve">ang. </s>
            <s xml:id="echoid-s717" xml:space="preserve">GFC; </s>
            <s xml:id="echoid-s718" xml:space="preserve">adeóque KI minimè penetrabit
              <lb/>
            medium BC, at reflectetur, puta in IH; </s>
            <s xml:id="echoid-s719" xml:space="preserve">tum IH refringatur in HS. </s>
            <s xml:id="echoid-s720" xml:space="preserve">
              <lb/>
            Ergò jam radiis ER, HS interjacens objectum puta RS radiis OG,
              <lb/>
            OK interjectum cernetur, velut ad ρ σ, ſitu partium everſo. </s>
            <s xml:id="echoid-s721" xml:space="preserve">Conſe-
              <lb/>
            quuntur hæc doctrinam noſtram, & </s>
            <s xml:id="echoid-s722" xml:space="preserve">experientiæ liquidò conſentanea
              <lb/>
            deprehendentur, quin & </s>
            <s xml:id="echoid-s723" xml:space="preserve">obſervatu dignum erit, è duplici refractione
              <lb/>
            ſpectatum objectum MNIridis coloribus tinctum adparere (rubro
              <lb/>
            ſcilicet ad μ, cæruleo ad ν, croceo medium occupante) objecti verò
              <lb/>
            RS è duplici refractione, ſed reflectione tamen intercedente, appre-
              <lb/>
            henſi imaginem ρ σ colore nihil ab ipſo objecto differre. </s>
            <s xml:id="echoid-s724" xml:space="preserve">Quod ex eo
              <lb/>
            ſanè videtur evenire, quoniam ang FEB angulo FGC æquatur; </s>
            <s xml:id="echoid-s725" xml:space="preserve">
              <lb/>
            adeóque radius KO non aliter è vitro exit, quam RE ingreſſus eſt;</s>
            <s xml:id="echoid-s726" xml:space="preserve"/>
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