Barrow, Isaac, Lectiones opticae & geometricae : in quibus phaenomenon opticorum genuinae rationes investigantur, ac exponuntur: et generalia curvarum linearum symptomata declarantur

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        <div xml:id="echoid-div166" type="section" level="1" n="20">
          <pb o="104" file="0122" n="122" rhead=""/>
          <p style="it">
            <s xml:id="echoid-s7017" xml:space="preserve">2. </s>
            <s xml:id="echoid-s7018" xml:space="preserve">Reliquis datis, lentem deſcribere.</s>
            <s xml:id="echoid-s7019" xml:space="preserve"/>
          </p>
          <note position="left" xml:space="preserve">Fig. 168.</note>
          <p>
            <s xml:id="echoid-s7020" xml:space="preserve">Sumantur ad arbitrium BY diſtantia lentis ab imagine, BD craſſi-
              <lb/>
            ties lentis, & </s>
            <s xml:id="echoid-s7021" xml:space="preserve">alter circulorum lentem conſtituentium ut (in hoc ex-
              <lb/>
            emplo) anterior EBF, cujus centrum ſit C; </s>
            <s xml:id="echoid-s7022" xml:space="preserve">& </s>
            <s xml:id="echoid-s7023" xml:space="preserve">ad iſta puncta B, D, C
              <lb/>
            erigantur BP, DQ, CI ad axin perpendiculares. </s>
            <s xml:id="echoid-s7024" xml:space="preserve">deinde per pun-
              <lb/>
            ctum A ducatur recta quævis API ſecans BP, & </s>
            <s xml:id="echoid-s7025" xml:space="preserve">CI in P, & </s>
            <s xml:id="echoid-s7026" xml:space="preserve">I. </s>
            <s xml:id="echoid-s7027" xml:space="preserve">fiat
              <lb/>
            CI. </s>
            <s xml:id="echoid-s7028" xml:space="preserve">CR :</s>
            <s xml:id="echoid-s7029" xml:space="preserve">: I. </s>
            <s xml:id="echoid-s7030" xml:space="preserve">R; </s>
            <s xml:id="echoid-s7031" xml:space="preserve">& </s>
            <s xml:id="echoid-s7032" xml:space="preserve">agatur RP ſecans DQ in Q. </s>
            <s xml:id="echoid-s7033" xml:space="preserve">fiat DQ. </s>
            <s xml:id="echoid-s7034" xml:space="preserve">DS :</s>
            <s xml:id="echoid-s7035" xml:space="preserve">:
              <lb/>
            I. </s>
            <s xml:id="echoid-s7036" xml:space="preserve">R; </s>
            <s xml:id="echoid-s7037" xml:space="preserve">& </s>
            <s xml:id="echoid-s7038" xml:space="preserve">agatur SY ſecans RP productam in ρ; </s>
            <s xml:id="echoid-s7039" xml:space="preserve">à quo demittatur
              <lb/>
            perpendicularis ρ K; </s>
            <s xml:id="echoid-s7040" xml:space="preserve">& </s>
            <s xml:id="echoid-s7041" xml:space="preserve">centro K intervallo DK deſeribatur circulus
              <lb/>
            EDF; </s>
            <s xml:id="echoid-s7042" xml:space="preserve">erit EBFD lens quæſita.</s>
            <s xml:id="echoid-s7043" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s7044" xml:space="preserve">Hîc autem in nimium excreſcenti ſpatium Lectioni defigatur limes.</s>
            <s xml:id="echoid-s7045" xml:space="preserve"/>
          </p>
        </div>
        <div xml:id="echoid-div173" type="section" level="1" n="21">
          <head xml:id="echoid-head24" xml:space="preserve">
            <emph style="sc">Lect.</emph>
          XV.</head>
          <p>
            <s xml:id="echoid-s7046" xml:space="preserve">BEne longo circa lucis reflectiones, quatenus hæ viſum afficiunt,
              <lb/>
            inſtituto ſtadio metam nunc opportunè ſixuri videmur, ea quomo-
              <lb/>
            docunque proſecuti, quæ πρ{ou}ρμαί{te}ρα nobis viſa, nec adeò pervulgata
              <lb/>
            ſe objecerant. </s>
            <s xml:id="echoid-s7047" xml:space="preserve">quod autem magnitudines objectas attinet (quas utique
              <lb/>
            de punctis tantùm radiantibus agentes omnino videamur omiſiſie)
              <lb/>
            quales nimirum illæ ex hujuſmodi radiorum inflectionibus quoad ſi-
              <lb/>
            tum, figuram, quantitatem mutationes ſubeunt, id fermè totum paſſim
              <lb/>
            atque fuſiùs tractatum proſtat, nec animus eſt mihi toties actum agere,
              <lb/>
            vel è trivio petita quæque huc transferre. </s>
            <s xml:id="echoid-s7048" xml:space="preserve">quin & </s>
            <s xml:id="echoid-s7049" xml:space="preserve">eò ſpectantia plera-
              <lb/>
            que cuncta de jam definitis ac oftenſis haud difficili negotio colligi
              <lb/>
            poſſe videntur; </s>
            <s xml:id="echoid-s7050" xml:space="preserve">ſingulorum nempe cujuſvis objecti punctorum (ex-
              <lb/>
            tremorum præſertim ac mediorum) apparentias indè determinando.
              <lb/>
            </s>
            <s xml:id="echoid-s7051" xml:space="preserve">verùm nec ea penitus neglectui habita, ad ſubſequentem quoque
              <lb/>
            regulam (ſeu monitiunculam) preſſiùs animum advertentes forſan
              <lb/>
            autumabitis. </s>
            <s xml:id="echoid-s7052" xml:space="preserve">Si qualem aſſignata quævis ſuperficies inflectens (ſim-
              <lb/>
            plex aut compoſita) magnltudinis cujuſvis expoſitæ ſpeciem exhibet
              <lb/>
            (ampliorem nempe vel contractiorem, directam aut inverſam, confuſam
              <lb/>
            diſtinctámve, ſeu quovis alio modo demutatam) internoſcere </s>
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