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-s8139" xml:space="preserve">XI. </s>
            <s xml:id="echoid-s8140" xml:space="preserve">Ità rectarum linearum ad ſphæricam ſuperſiciem ex inſlectione
              <lb/>
            quavis procreatas imagines qualitercunque liceat definire. </s>
            <s xml:id="echoid-s8141" xml:space="preserve">unde de
              <lb/>
            planarum quoque ſuperſicierum ad eandem repræſentationibus haud
              <lb/>
            difficilè ſtatuetur; </s>
            <s xml:id="echoid-s8142" xml:space="preserve">harum ſcilicet imagines abſolutæ _conoidum aut_
              <lb/>
            _Sphæroidum Superſicies erunt_ è rectarum imaginibus reſpectivis circa
              <lb/>
            radiationum axes converſis progenitæ; </s>
            <s xml:id="echoid-s8143" xml:space="preserve">quin & </s>
            <s xml:id="echoid-s8144" xml:space="preserve">relatæ quoque pla-
              <lb/>
            narum ſuperficierum imagines è rectarum imaginibus relatis ſimili
              <lb/>
            pacto progenerantur. </s>
            <s xml:id="echoid-s8145" xml:space="preserve">rem totam ipſi mentem aliquantillùm adver-
              <lb/>
            tentes perſpicietis; </s>
            <s xml:id="echoid-s8146" xml:space="preserve">me λεπτολογιας
              <unsure/>
            extremæ faſtidium capit.</s>
            <s xml:id="echoid-s8147" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s8148" xml:space="preserve">XII. </s>
            <s xml:id="echoid-s8149" xml:space="preserve">Reſtare videtur, ut quomodò compoſitæ ſuperficies ſphæricæ
              <lb/>
            objectas repræſentant lineas diſpiciamus. </s>
            <s xml:id="echoid-s8150" xml:space="preserve">verum cum imagines indè
              <lb/>
            prognatæ ſint altioris gradûs lineæ, ab uſu notitiàque communi ſegre-
              <lb/>
            gatæ, atque proprietatibus intricatis præditæ; </s>
            <s xml:id="echoid-s8151" xml:space="preserve">nil aliud quàm operam
              <lb/>
            luderem iis deſudans extricandis. </s>
            <s xml:id="echoid-s8152" xml:space="preserve">illas itaque tranſiliam; </s>
            <s xml:id="echoid-s8153" xml:space="preserve">hoc com-
              <lb/>
            monens unicum, punctorum in illis aliquot principalium poſitiones è
              <lb/>
            præmonſtratis dignoſci, de cæteris commodiùs ex conjectura diju-
              <lb/>
            dicari.</s>
            <s xml:id="echoid-s8154" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s8155" xml:space="preserve">XIII Hæc ſunt, quæ circa partem _Opticæ_ præcipuè _Mathemati-_
              <lb/>
            _cam_ dicenda mihi ſuggeſſit meditatio. </s>
            <s xml:id="echoid-s8156" xml:space="preserve">circa reliquas (quæ φυσικώτε{ρο}ι
              <lb/>
            ſunt, adeóqve ſæpiuſculè pro certis principiis plauſibiles conjecturas
              <lb/>
            venditare neceſſum habent) nihil ferè quicquam admodum veriſimile
              <lb/>
            ſuccurrit, à pervulgatis (ab iis, inquam, quæ _Keplerus, Sche@ner@s,_
              <lb/>
            _Carteſius_, & </s>
            <s xml:id="echoid-s8157" xml:space="preserve">poſt illos alii tradiderunt) alienum aut diverſum: </s>
            <s xml:id="echoid-s8158" xml:space="preserve">atqui
              <lb/>
            tacere malo, quàm toties oblatam cramben reponere. </s>
            <s xml:id="echoid-s8159" xml:space="preserve">proinde re-
              <lb/>
              <handwritten xlink:label="hd-0143-01" xlink:href="hd-0143-01a" number="4"/>
            ceptui cano; </s>
            <s xml:id="echoid-s8160" xml:space="preserve">nec ità tamen ut prorſus diſcedam, anteaquàm impro-
              <lb/>
            bam quandam diſſicultatem (pro ſinceritate quam & </s>
            <s xml:id="echoid-s8161" xml:space="preserve">vobis & </s>
            <s xml:id="echoid-s8162" xml:space="preserve">veritati
              <lb/>
            debeo minimè diſſimulandam) in medium protulero, quæ doctrinæ
              <lb/>
            noſtræ, hactenus inculcatæ, ſe objicit adverſam, ab ea ſaltem nul-
              <lb/>
            lam admittit ſolutionem. </s>
            <s xml:id="echoid-s8163" xml:space="preserve">illa, breviter, talis eſt: </s>
            <s xml:id="echoid-s8164" xml:space="preserve">_Lenti vel ſpeculo_
              <lb/>
              <note position="right" xlink:label="note-0143-01" xlink:href="note-0143-01a" xml:space="preserve">Fig. 202,
                <lb/>
              203,</note>
            _cavo_ EBF exponatur viſibile punctum A, ità diſtans, ut radii ab A
              <lb/>
            manantes ex inflectione verſus axem AB cogantur; </s>
            <s xml:id="echoid-s8165" xml:space="preserve">si
              <unsure/>
            tque radiationis
              <lb/>
            limes (ſeu puncti A imago, qualem ſupra paſſim ſtatuimus) pun-
              <lb/>
            ctum Z; </s>
            <s xml:id="echoid-s8166" xml:space="preserve">inter hoc autem & </s>
            <s xml:id="echoid-s8167" xml:space="preserve">inflectentis verticem B uſpiam poſitus
              <lb/>
            concipiatur oculus. </s>
            <s xml:id="echoid-s8168" xml:space="preserve">quæri jam poteſt, ubi loci debeat punctum A ap-
              <lb/>
            parere. </s>
            <s xml:id="echoid-s8169" xml:space="preserve">retrorſum ad punctum Z videri natura non fert (cùm omnis
              <lb/>
            impreſſio ſenſum aſſiciens proveniat a partibus A) ac experientia re-
              <lb/>
            clamat. </s>
            <s xml:id="echoid-s8170" xml:space="preserve">noſtris autem è placitis conſequi videtur ipſum, ad partes </s>
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