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