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-s493" xml:space="preserve">
              <pb o="12" file="0030" n="30" rhead=""/>
            ſpecularis; </s>
            <s xml:id="echoid-s494" xml:space="preserve">hæc utique circulum continget; </s>
            <s xml:id="echoid-s495" xml:space="preserve">(quia ſpeculi planum, ex
              <lb/>
            hypotheſi, non alibi præterquam ad B circulo occurrit, adeóque nec
              <lb/>
            rec
              <unsure/>
            ta G H) quare rectæ G H, O P ſunt parallelæ. </s>
            <s xml:id="echoid-s496" xml:space="preserve">Ergo P O eſt ad
              <lb/>
            ſpeculi planum parallela. </s>
            <s xml:id="echoid-s497" xml:space="preserve">Huic verò perpendicularia ſunt plana præ-
              <lb/>
            dicta cylindrum contingentia per M O, N P ducta; </s>
            <s xml:id="echoid-s498" xml:space="preserve">axi parallela.
              <lb/>
            </s>
            <s xml:id="echoid-s499" xml:space="preserve">Quapropter eadem ſpeculi plano recta erunt. </s>
            <s xml:id="echoid-s500" xml:space="preserve">Hinc, ut anteà ſi totus
              <lb/>
            radius habeatur inſtar rectæ lineæ, continget ejus reflectio velut in ſu-
              <lb/>
            perficie ad ſpeculum planum recta; </s>
            <s xml:id="echoid-s501" xml:space="preserve">quippe cùm ejus latitudo tota com-
              <lb/>
            prehendatur inter ejuſniodi duo plana; </s>
            <s xml:id="echoid-s502" xml:space="preserve">quæ proinde ſi nulla ſuppona-
              <lb/>
            tur, in unum illa coaleſcent. </s>
            <s xml:id="echoid-s503" xml:space="preserve">Accommodari poſſent hæc cuicunque
              <lb/>
            radii figuræ tali, qualem ſupra deſcripſimus, utcunque nonnulla de-
              <lb/>
            mutando; </s>
            <s xml:id="echoid-s504" xml:space="preserve">ſed & </s>
            <s xml:id="echoid-s505" xml:space="preserve">eadem pari ratione radiorum refractionibus adapten-
              <lb/>
            tur. </s>
            <s xml:id="echoid-s506" xml:space="preserve">Atpluribus parco.</s>
            <s xml:id="echoid-s507" xml:space="preserve"/>
          </p>
        </div>
        <div xml:id="echoid-div13" type="section" level="1" n="10">
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            <emph style="sc">Lect.</emph>
          II.</head>
          <p>
            <s xml:id="echoid-s508" xml:space="preserve">1. </s>
            <s xml:id="echoid-s509" xml:space="preserve">V Iæ, quam nuper aperuimus, & </s>
            <s xml:id="echoid-s510" xml:space="preserve">aliquatenus ingreſſi ſumus,
              <lb/>
            inhærentes eò jam devenimus, ut nobis incumbat proximè
              <lb/>
            celebres illas hypotheſes (an Theoremata malitis appellare) radiorum
              <lb/>
            inflexorum itineri penitus determinando (imaginúmque proinde locis,
              <lb/>
            figuris, quantitatibus inveſtigandis, nec non apparentiarum quarum-
              <lb/>
            cunque cauſis explicandis) neceſſarias, experientiæ quidem bene con-
              <lb/>
            ſonas illas, etiam aliquo rationis ſuffragio communire; </s>
            <s xml:id="echoid-s511" xml:space="preserve">præſtratis
              <lb/>
            utique ſundamentis, ac ſuppoſitionibus inſiſtendo. </s>
            <s xml:id="echoid-s512" xml:space="preserve">Cùm itaque lucis
              <lb/>
            radio corpus adſignatum ſit figurâ priſmaticum, aut cylindricum; </s>
            <s xml:id="echoid-s513" xml:space="preserve">Et
              <lb/>
            hoc quidem rectum (utpote præ reliquis ſimplex, & </s>
            <s xml:id="echoid-s514" xml:space="preserve">naturæ totas ſuas
              <lb/>
            in agendo vires exerenti præſertim conveniens;) </s>
            <s xml:id="echoid-s515" xml:space="preserve">cùm & </s>
            <s xml:id="echoid-s516" xml:space="preserve">exinde pro-
              <lb/>
            greſſus ejus eatenus fuerit definitus, ut intra ſuperficies duas planas in-
              <lb/>
            Hectenti medio perpendiculares includatur; </s>
            <s xml:id="echoid-s517" xml:space="preserve">quas quidem abhinc (quan-
              <lb/>
            do nullus tranſverſæ dimenſionis illius, vel intervalli ſuperficies iſtas
              <lb/>
            dirimentis ad rem noſtram, illam ſaltem quam nunc attingimus ſpe-
              <lb/>
            ctans effectus, aut uſus ſit) brevitatis & </s>
            <s xml:id="echoid-s518" xml:space="preserve">perſpicuitatis cauſâ, velut u-
              <lb/>
            nam habere poſſumus; </s>
            <s xml:id="echoid-s519" xml:space="preserve">adeóque jam radium ut duabus ſolummodò di-
              <lb/>
            menſionibus præditum, & </s>
            <s xml:id="echoid-s520" xml:space="preserve">ad inſtar Parallelogrammi cujuſdam rect-
              <lb/>
            anguli, in plano ad medii inflectentis ſuperficiem recto jacentis, con-
              <lb/>
            fiderantes, reliquam itineris quod perſequitur determinationem, </s>
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