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

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        <div xml:id="echoid-div58" type="section" level="1" n="14">
          <pb o="47" file="0065" n="65"/>
        </div>
        <div xml:id="echoid-div72" type="section" level="1" n="15">
          <head xml:id="echoid-head18" xml:space="preserve">
            <emph style="sc">Lect</emph>
          . VI.</head>
          <p>
            <s xml:id="echoid-s2599" xml:space="preserve">I. </s>
            <s xml:id="echoid-s2600" xml:space="preserve">ABſolutis iis, quæ radiis accidunt ad planam ſuperficiem in-
              <lb/>
            flexis (obſervatu quæ videbantur non indigna, cúmque: </s>
            <s xml:id="echoid-s2601" xml:space="preserve">prin-
              <lb/>
            cipiis noſtris cohærentia; </s>
            <s xml:id="echoid-s2602" xml:space="preserve">quæ denuò viam ſternebant, aut metho-
              <lb/>
            dum aperiebant ſequentibus) ad curvas jam gradum promovemus;
              <lb/>
            </s>
            <s xml:id="echoid-s2603" xml:space="preserve">circa quas equidem cogitâram communia quædam delibare; </s>
            <s xml:id="echoid-s2604" xml:space="preserve">verùm
              <lb/>
            excuſſà re, tam exilem illam & </s>
            <s xml:id="echoid-s2605" xml:space="preserve">abſtractam deprehendo, ſatius ut
              <lb/>
            exiſtimem actutùm ad particularia deſcendere. </s>
            <s xml:id="echoid-s2606" xml:space="preserve">curvarum utique prin-
              <lb/>
            cipem, & </s>
            <s xml:id="echoid-s2607" xml:space="preserve">ad praxes Opticas longè paratiſſimam, Superficiem Sphæ-
              <lb/>
            ricam aggrediar è veſtigio. </s>
            <s xml:id="echoid-s2608" xml:space="preserve">pro qua tamen, ob cauſas pridem aſſigna-
              <lb/>
            tas, circulos ſubrogabo per oculi Sphæræque centra, pérque ſingula
              <lb/>
            radiantia puncta trajectos. </s>
            <s xml:id="echoid-s2609" xml:space="preserve">& </s>
            <s xml:id="echoid-s2610" xml:space="preserve">quoad hos _Catoptrica_ primo, _D@op-_
              <lb/>
            _trica_ poſtmodum exequemur. </s>
            <s xml:id="echoid-s2611" xml:space="preserve">Ad illa.</s>
            <s xml:id="echoid-s2612" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s2613" xml:space="preserve">II. </s>
            <s xml:id="echoid-s2614" xml:space="preserve">Præſternemus autem _λημμdηον_ unum vel alterum; </s>
            <s xml:id="echoid-s2615" xml:space="preserve">hoc impri-
              <lb/>
            mìs: </s>
            <s xml:id="echoid-s2616" xml:space="preserve">Incidenti@m circulo radiorum obliquior eſt, qui magis à centro
              <lb/>
              <note position="right" xlink:label="note-0065-01" xlink:href="note-0065-01a" xml:space="preserve">Fig. 62.</note>
            diſtat; </s>
            <s xml:id="echoid-s2617" xml:space="preserve">vel qui minorem arcum (ſubſemicircularem) ſubtendit. </s>
            <s xml:id="echoid-s2618" xml:space="preserve">ſci-
              <lb/>
            licet obliquiùs incidit recta QRS, quàm recta MNP. </s>
            <s xml:id="echoid-s2619" xml:space="preserve">Nam à
              <lb/>
            centro C ducantur CN, CP; </s>
            <s xml:id="echoid-s2620" xml:space="preserve">& </s>
            <s xml:id="echoid-s2621" xml:space="preserve">CR; </s>
            <s xml:id="echoid-s2622" xml:space="preserve">CS. </s>
            <s xml:id="echoid-s2623" xml:space="preserve">& </s>
            <s xml:id="echoid-s2624" xml:space="preserve">quoniam angulus
              <lb/>
            RCS angulo NCP (hypotheſi nimirum inſiſtendo) minor eſt;
              <lb/>
            </s>
            <s xml:id="echoid-s2625" xml:space="preserve">pater reliquos CRS, CSR reliquos CN, P, CPN (cùm junctim,
              <lb/>
            tum ſingulum ſingulo) majores eſſe. </s>
            <s xml:id="echoid-s2626" xml:space="preserve">Cùm itaque Semidiametxi
              <lb/>
            CR, CN, circumferentiæ perpendiculares ſint; </s>
            <s xml:id="echoid-s2627" xml:space="preserve">omninò liquet pro-
              <lb/>
            poſitum.</s>
            <s xml:id="echoid-s2628" xml:space="preserve"/>
          </p>
          <p style="it">
            <s xml:id="echoid-s2629" xml:space="preserve">III. </s>
            <s xml:id="echoid-s2630" xml:space="preserve">Dato radio MN ad circulum incidenti congruum reflexum
              <lb/>
            reſignare.</s>
            <s xml:id="echoid-s2631" xml:space="preserve"/>
          </p>
          <note position="right" xml:space="preserve">Fig. 63.</note>
          <p>
            <s xml:id="echoid-s2632" xml:space="preserve">Variis modis huc facilè peragitur; </s>
            <s xml:id="echoid-s2633" xml:space="preserve">quorum nunc unum adhibere,
              <lb/>
            tunc alium ex uſu ſit. </s>
            <s xml:id="echoid-s2634" xml:space="preserve">nos unum aut alterum ex expeditoribus attinge-
              <lb/>
            mus. </s>
            <s xml:id="echoid-s2635" xml:space="preserve">i. </s>
            <s xml:id="echoid-s2636" xml:space="preserve">Incidens MN protrahatur ut circulum denuò ſecet in P. </s>
            <s xml:id="echoid-s2637" xml:space="preserve">;
              <lb/>
            </s>
            <s xml:id="echoid-s2638" xml:space="preserve">& </s>
            <s xml:id="echoid-s2639" xml:space="preserve">ſumatur arcus N Π = NP; </s>
            <s xml:id="echoid-s2640" xml:space="preserve">erit connexa Π NH ipſius MNP
              <lb/>
            reflexus. </s>
            <s xml:id="echoid-s2641" xml:space="preserve">nam à centro C connexâ CN, manifeſtum eſt </s>
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