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-s648" xml:space="preserve">
              <pb o="17" file="0035" n="35" rhead=""/>
            cujuſmodi quippe de cauſis diaphanum ſubinde forſan evaſurum eſt
              <lb/>
            opacum, & </s>
            <s xml:id="echoid-s649" xml:space="preserve">inſtar opaciradios valebit repercútere; </s>
            <s xml:id="echoid-s650" xml:space="preserve">ceu quando lapis
              <lb/>
            in aquam impingit obliquè; </s>
            <s xml:id="echoid-s651" xml:space="preserve">cùm hydrargyro ſubſtracto vitrum mu-
              <lb/>
            nitur. </s>
            <s xml:id="echoid-s652" xml:space="preserve">Dum lapis _e. </s>
            <s xml:id="echoid-s653" xml:space="preserve">g._ </s>
            <s xml:id="echoid-s654" xml:space="preserve">obliquè impingit ſuperficiei EF (cui parallela
              <lb/>
            OQ) per lineam AB; </s>
            <s xml:id="echoid-s655" xml:space="preserve">tota linea BQ ad fundum OQ protenſa
              <lb/>
            venienti repugnabit, auxilii quoque nonnihil conferente fundo OQ;
              <lb/>
            </s>
            <s xml:id="echoid-s656" xml:space="preserve">neque mirum fuerit, ſi major hic renitentia deprehendatur, quam ubi
              <lb/>
            radius alter MBP perpendiculariús incurrit, quando major ſit BQ,
              <lb/>
            quam BP.</s>
            <s xml:id="echoid-s657" xml:space="preserve">] At nos ſecluſis iſtis medium velut interminatum, in om-
              <lb/>
            nes partes æqualiter reſiſtens, abſolutè perſpicuum, & </s>
            <s xml:id="echoid-s658" xml:space="preserve">radios ex ſe
              <lb/>
            non reſpuens accipimus; </s>
            <s xml:id="echoid-s659" xml:space="preserve">quibus ſuppoſitis perpetuò, quod dixi, ra-
              <lb/>
            dius, obliquitate quâpiam incidentiæ nil vetante, medium denſius pe-
              <lb/>
            netrabit. </s>
            <s xml:id="echoid-s660" xml:space="preserve">Verum in alterò caſu, cùm de medio denſiori lux rarius in-
              <lb/>
            currit, non ſemper ea medium hoc permeabit. </s>
            <s xml:id="echoid-s661" xml:space="preserve">Nam ſi magna ſatìs
              <lb/>
            fuerit obliquitas; </s>
            <s xml:id="echoid-s662" xml:space="preserve">ſubinde radius inflexus ſupra ſuperficiem EF at-
              <lb/>
            tolletur, angulúſque (qui dicitur) refractus, aut inflexus rectum ex-
              <lb/>
            ſuperabit; </s>
            <s xml:id="echoid-s663" xml:space="preserve">quinimò fieri poteſt ut ipſum exæquet. </s>
            <s xml:id="echoid-s664" xml:space="preserve">Sit in exemplum
              <lb/>
            primò inclinatio graduum 45, vel ſemirecta; </s>
            <s xml:id="echoid-s665" xml:space="preserve">Et ZB ad ZD ſe habe-
              <lb/>
            at ut quadrati diameter ad ſuum latus quæ fermè proportio radiorum
              <lb/>
            ex aqua in aerem tranſeuntium, experientiâ conteſtante, rationem
              <lb/>
              <note position="right" xlink:label="note-0035-01" xlink:href="note-0035-01a" xml:space="preserve">Fig. 12.</note>
            metitur) radius velut in ipſam EF refringetur, aut eam ſtringens pro-
              <lb/>
            cedet. </s>
            <s xml:id="echoid-s666" xml:space="preserve">Eſt enim Z δ (æqualis ipſi ZD) jam ad EF perpendicularis,
              <lb/>
            adeoque δ κ arcum δ D contingens ipſi EF congruet. </s>
            <s xml:id="echoid-s667" xml:space="preserve">Unde patet
              <lb/>
            obiter, id quod ſuperiùs inſinuatum, non univerſim conſtare, quòd
              <lb/>
            radius à quo loco medii unius in aliud proceſſit, ad eundem retrogra-
              <lb/>
            dus accedet. </s>
            <s xml:id="echoid-s668" xml:space="preserve">Hoc enim ſaltem in caſu radius AB refringitur in β α ſu-
              <lb/>
            perficiei media dirimenti parallelam; </s>
            <s xml:id="echoid-s669" xml:space="preserve">veruntamen qui per α β progre-
              <lb/>
            ditur minjmè recedet ad BA, nec ullam, ut manifeſtum eſt, omninò
              <lb/>
            refractionem patietur. </s>
            <s xml:id="echoid-s670" xml:space="preserve">Sed hic caſus tantùm unus, & </s>
            <s xml:id="echoid-s671" xml:space="preserve">quaſi pro nullo
              <lb/>
            cenſeri poteſt. </s>
            <s xml:id="echoid-s672" xml:space="preserve">Quod ſi, ſervatâ quoad denſitatem eâdem proportione,
              <lb/>
              <note position="right" xlink:label="note-0035-02" xlink:href="note-0035-02a" xml:space="preserve">Fig. 13.</note>
            radius AB paullò magis ad rectam EF inclinetur, ejus. </s>
            <s xml:id="echoid-s673" xml:space="preserve">Refractus
              <lb/>
            ſupra ipſam EF aſſurget; </s>
            <s xml:id="echoid-s674" xml:space="preserve">punctum quippe D rectam EF nunquam
              <lb/>
            pertinget; </s>
            <s xml:id="echoid-s675" xml:space="preserve">& </s>
            <s xml:id="echoid-s676" xml:space="preserve">punctum B decurſâ rarius intra medium peripheriâ
              <lb/>
            B β in denſum remeabit; </s>
            <s xml:id="echoid-s677" xml:space="preserve">in quo proinde rurſus, circulatione ſuâ di-
              <lb/>
            miſſà, per tangentes β α, δ κ ferentur; </s>
            <s xml:id="echoid-s678" xml:space="preserve">adeò quidem ut radius ABCD
              <lb/>
            jam reflecti videatur, quatenus medium denſius haud penetrat totus,
              <lb/>
            vel egreditur.</s>
            <s xml:id="echoid-s679" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s680" xml:space="preserve">VI. </s>
            <s xml:id="echoid-s681" xml:space="preserve">Nec ineptè quidem (etſi quodammodò, velutíque primariò, ſit
              <lb/>
            refractio) reflectionis nomen adſciſcit hæc actio, quatenus & </s>
            <s xml:id="echoid-s682" xml:space="preserve"/>
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