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-s414" xml:space="preserve">
              <pb o="9" file="0027" n="27" rhead=""/>
            deprehendi. </s>
            <s xml:id="echoid-s415" xml:space="preserve">Quod ſanè mihi tam verum apparet, ut non dubitem
              <lb/>
            hancipſam hypotheſin ad omnimodos incurſus extendere; </s>
            <s xml:id="echoid-s416" xml:space="preserve">ſeu genera-
              <lb/>
            tim effari, quod pulſus omnis & </s>
            <s xml:id="echoid-s417" xml:space="preserve">motus, utcunque medio culibet im-
              <lb/>
            pingens, directè (per ſe nimirum, propriè, diſtinctéque rem eſti-
              <lb/>
            mando) continuatur, aut prorſum aut retrorſum. </s>
            <s xml:id="echoid-s418" xml:space="preserve">Scilicet, exempli
              <lb/>
            cauſà ſi duo baculi A B Y Z, C D Y Z in idem medium E F (illud
              <lb/>
            perpendiculariter, hoc obliquè) uniformi quâdam preſſione vel impe-
              <lb/>
            tu adigantur, exiſtimo medii ceſſione vel reſiſtentiâ totam (quâ bacu-
              <lb/>
            lus obliquus fertur, aut medium impellit) vim æquè rectâ ſemità an-
              <lb/>
            trorſum verſus I K, vel retrò verſus C D derivari, ac perpendicularis
              <lb/>
            ipſius impetus in G H progreditur, aut regreditur in A B. </s>
            <s xml:id="echoid-s419" xml:space="preserve">Quod
              <lb/>
            enim nonnulli putant medii ſuperficiem baculi perpendicularis tenden-
              <lb/>
            tiæ magìs opponi, quam obliqui, proindéque perpendicularis impul-
              <lb/>
            ſum rectà continuari, ſed obliquum alio detorqueri; </s>
            <s xml:id="echoid-s420" xml:space="preserve">vel aſſertionem
              <lb/>
            ipſam non agnoſco, vel non admitto conſequentiam. </s>
            <s xml:id="echoid-s421" xml:space="preserve">Enimverò ſi per
              <lb/>
            illud opponi nil aliud volunt quàm realiter objici, ſeu obſtare recta
              <lb/>
            pergenti, non minùs eo modo ſuperſicies E F opponitur baculo C D,
              <lb/>
              <note position="right" xlink:label="note-0027-01" xlink:href="note-0027-01a" xml:space="preserve">Fig. 1.</note>
            quàm ipſi A B; </s>
            <s xml:id="echoid-s422" xml:space="preserve">rectum enim ejus progreſſum pariter intercipit, im-
              <lb/>
            pedit, demutat. </s>
            <s xml:id="echoid-s423" xml:space="preserve">Verùm ſi quam aliam neſcio quam imaginariam op-
              <lb/>
            poſitionem intelligunt, nihil video quod huc faciat indè conſectari.
              <lb/>
            </s>
            <s xml:id="echoid-s424" xml:space="preserve">Proſectò rem abſtractè, nec ut accidentarium quid immiſceamus, ex-
              <lb/>
            pendendo, nihil attinet ullam medii partem conſiderare præter illam,
              <lb/>
            ad quam corpus progrediens aut propellens ei occurrit; </s>
            <s xml:id="echoid-s425" xml:space="preserve">hæc enim ſola
              <lb/>
            reſiſtendo quicquam efficit, aut cedendo. </s>
            <s xml:id="echoid-s426" xml:space="preserve">Quare per rectam D Z pro-
              <lb/>
            gredienti impulſui ſolum punctum Z opponitur; </s>
            <s xml:id="echoid-s427" xml:space="preserve">perindéque fuerit
              <lb/>
            qualem reliqua medii ſuperficies obtinere ſitum concipiatur. </s>
            <s xml:id="echoid-s428" xml:space="preserve">Punctum
              <lb/>
            autem Z æquè pulſui venienti à D perrectam D Z, atque tendenti per
              <lb/>
            rectam Z K verſus K contrariatur, ac ei qui à B per B Z procedens iter
              <lb/>
            affectat per Z H verſus H. </s>
            <s xml:id="echoid-s429" xml:space="preserve">Idémque de reliquis medii punctis intelligi
              <lb/>
            par eſt, quibus uterque baculus ipſum contingit, aut ei applicatur. </s>
            <s xml:id="echoid-s430" xml:space="preserve">
              <lb/>
            Itaque reverà par utriuſque pulſùs quoad oppoſitionem eſt ratio; </s>
            <s xml:id="echoid-s431" xml:space="preserve">ſimi-
              <lb/>
            líſque proinde utrobique reſultabit effectus; </s>
            <s xml:id="echoid-s432" xml:space="preserve">pulſumnempe recto tra-
              <lb/>
            mite vel tranſmittere, vel rejicere. </s>
            <s xml:id="echoid-s433" xml:space="preserve">Verùm longè ſecus eveniet, ſi ba-
              <lb/>
            culum alterum obliquum, ſeu P D Y Q, cum ipſo A B Y Z confera-
              <lb/>
            mus Etenim ſuperſicies E F baculi A B Y Z motui, vel impulſui
              <lb/>
            magìs opponitur, aut obſiſtit, quàm motui vel impulſui baculi P D Y Q. </s>
            <s xml:id="echoid-s434" xml:space="preserve">
              <lb/>
            Quoniam illi toti cum tota ſui parte Y Z, huic vero tantum ex parte Y
              <lb/>
            renititur. </s>
            <s xml:id="echoid-s435" xml:space="preserve">è qua diſcrepantia neceſſariò diſpar effectus conſequetur, ut
              <lb/>
            nimirum pulſùs aut motûs directio mutetur. </s>
            <s xml:id="echoid-s436" xml:space="preserve">Quod diſcrimen eò lu-
              <lb/>
            bentius adnoto, quoniam hoc arbitror modo (vel adſimili) lucis </s>
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