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-s726" xml:space="preserve">
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            ſeu quicquid retractio ad E effecit, id refractio ad K retexit, radium in
              <lb/>
            ſtatum reſtituens, ei quem ab origine habuit non diſparem. </s>
            <s xml:id="echoid-s727" xml:space="preserve">Verùm
              <lb/>
            hæc non eſt hujus loci penitiùs excutere, Saltem obſervari meretur hoc
              <lb/>
            præcipuum, ut arbitror, in priſmate Phænomenon.</s>
            <s xml:id="echoid-s728" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s729" xml:space="preserve">VIII. </s>
            <s xml:id="echoid-s730" xml:space="preserve">Hæc, inquam, cùm ab experientia confirmentur, neque tamen
              <lb/>
            ei magis, quam ratiociniis noſtris conſentiant, cauſis tamen adſcribun-
              <lb/>
            tur (à quibuſdam) nedum diverſis, at prorſus adverſis. </s>
            <s xml:id="echoid-s731" xml:space="preserve">Quòd enim
              <lb/>
            vitrum _e. </s>
            <s xml:id="echoid-s732" xml:space="preserve">g_. </s>
            <s xml:id="echoid-s733" xml:space="preserve">radios intra corpus ſuum receptos, ejúſque poſticæ ſuper-
              <lb/>
            ficiei obliquius incidentes retrocedere cogat, hujuſmodi rationem exhi-
              <lb/>
            bent: </s>
            <s xml:id="echoid-s734" xml:space="preserve">aiunt vitrum radios faciliùs admittere, vel tranſmittere quàm
              <lb/>
            aërem; </s>
            <s xml:id="echoid-s735" xml:space="preserve">quin addunt aërem vi reflectendi prævalidâ pollere; </s>
            <s xml:id="echoid-s736" xml:space="preserve">quódque
              <lb/>
            proinde qui poſt vitrum adventanti radio fit obvius aër cum reverbe-
              <lb/>
            rat. </s>
            <s xml:id="echoid-s737" xml:space="preserve">Quæ ratio mihi non adblanditur. </s>
            <s xml:id="echoid-s738" xml:space="preserve">Nam imprimis rei naturæ mi-
              <lb/>
            nùs conſentanea videtur. </s>
            <s xml:id="echoid-s739" xml:space="preserve">Quum enim aëris corpus ex æthere puro
              <lb/>
            maximam partem, è corpuſculis terrenis, & </s>
            <s xml:id="echoid-s740" xml:space="preserve">ex halitibus aqueis con-
              <lb/>
            ſtare totum videatur; </s>
            <s xml:id="echoid-s741" xml:space="preserve">ex his partibus æther, opinor, non minùs
              <lb/>
            promptè quàm vitrum radios tranſmitti; </s>
            <s xml:id="echoid-s742" xml:space="preserve">aqua vero ſaltem (ex illo-
              <lb/>
            rum, quibuſcum diſputamus, ſententiâ) tantillo difficiliùs; </s>
            <s xml:id="echoid-s743" xml:space="preserve">adeóque
              <lb/>
            neutiquam harum alterutri dicta reflectio jure videtur attribuenda;
              <lb/>
            </s>
            <s xml:id="echoid-s744" xml:space="preserve">terreſtres autem particulæ (quæ præ reliquis etiam pauciores videntur,
              <lb/>
            & </s>
            <s xml:id="echoid-s745" xml:space="preserve">rariùs interſperſæ, præſertim in aëre ſudo ſummíſque; </s>
            <s xml:id="echoid-s746" xml:space="preserve">montium ex-
              <lb/>
            celſorum jugis) ſunt opacæ, nec lucem admittunt, aſt eam in omni-
              <lb/>
            cunque pariter incidentiâ rejiciunt; </s>
            <s xml:id="echoid-s747" xml:space="preserve">adeò ut nec ad has quam reſpici-
              <lb/>
            mus lucis inflectio propriè ſpectet; </s>
            <s xml:id="echoid-s748" xml:space="preserve">ergò nihil ſubeſſe videtur cauſæ, cur
              <lb/>
            aër (præ vitro) ingruenti luci potentiùs obſiſtat. </s>
            <s xml:id="echoid-s749" xml:space="preserve">Addo; </s>
            <s xml:id="echoid-s750" xml:space="preserve">ſi talis aëri vis
              <lb/>
            reflexiva competat, & </s>
            <s xml:id="echoid-s751" xml:space="preserve">vera ſit, quam hi Philoſophi memorato Phæ-
              <lb/>
            nomeno cauſam adſignant, conſequi videtur, ut nulla prope Horizon-
              <lb/>
            tem Stella conſpici poſſit (admiſſo ſaltem hoc, non inverecundo reor,
              <lb/>
            ut pleriſque viſum erit, poftulato; </s>
            <s xml:id="echoid-s752" xml:space="preserve">quòd purus Æther, naturale lucis
              <lb/>
            vehiculum, aëreæ regioni ſuprajectus haud mînùs facile quàm vitrum
              <lb/>
            aut aqua radios intromittet.) </s>
            <s xml:id="echoid-s753" xml:space="preserve">Sit enim C terræ centrum, O oculus,
              <lb/>
            S viſibile punctum longinquum, ceu ſtella, ſitum in Horizonte; </s>
            <s xml:id="echoid-s754" xml:space="preserve">per
              <lb/>
              <note position="right" xlink:label="note-0037-01" xlink:href="note-0037-01a" xml:space="preserve">Fig. 14.</note>
            puncta verò C, O, S trajectum concipiatur planum faciens in terræ ſu-
              <lb/>
            perficie circùlum OP; </s>
            <s xml:id="echoid-s755" xml:space="preserve">in atmoſphæræ, vel aëris circumfuſi, extima
              <lb/>
            ſuperficie circumferentiam ZNM; </s>
            <s xml:id="echoid-s756" xml:space="preserve">itaque cum radius quilibet, ut
              <lb/>
            SM, vel SN (Horizontalis puta, vel eò ſuperior) in ſuperficiem MZ
              <lb/>
            cadens ei incidat perquam obliquè (niſi ſaltem atmoſphæræ Semidi-
              <lb/>
            ameter CZ præ telluris Semidiametro CO dicatur enormiter, & </s>
            <s xml:id="echoid-s757" xml:space="preserve">in-
              <lb/>
            credibiliter magna) cùm & </s>
            <s xml:id="echoid-s758" xml:space="preserve">aer idcircò, juxta ſententiam quam </s>
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