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

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          <pb o="109" file="0127" n="127" rhead=""/>
          <p>
            <s xml:id="echoid-s7276" xml:space="preserve">Huic effato ſi contraria obtendatur experientia, monſtrans ſubinde
              <lb/>
            duntaxat unam imaginem apparere; </s>
            <s xml:id="echoid-s7277" xml:space="preserve">regero, in refractione quidem
              <lb/>
            ad ſuperficiem planam apparenter hoc plerumque contingere, quo-
              <lb/>
            niam imagines iſtæ duæ (quales α, _a_) ita ſibimet ipſis, ita refracto-
              <lb/>
            rum concurſui X vicinæ ſunt, ut ipſarum intervallum diſcerni nequeat,
              <lb/>
            ipſæque (ſicut in ſimili caſu obvenire mox oſtendemus) velut in unam
              <lb/>
            imaginem interceptibilitèr coaleſcant; </s>
            <s xml:id="echoid-s7278" xml:space="preserve">aſt in aliis diverſi generis in-
              <lb/>
            flectionibus, etiam ſenſu conteſtante, maniſeſtè ſecùs apparet; </s>
            <s xml:id="echoid-s7279" xml:space="preserve">id
              <lb/>
            quod cùm è compluribus admodum obviis experimentis conſtare poſſit,
              <lb/>
            unum ſaltem ac alterum proponemns. </s>
            <s xml:id="echoid-s7280" xml:space="preserve">Speculo BNM exponatur ob-
              <lb/>
              <note position="right" xlink:label="note-0127-01" xlink:href="note-0127-01a" xml:space="preserve">Fig. 177,
                <lb/>
              178.</note>
            jectum A; </s>
            <s xml:id="echoid-s7281" xml:space="preserve">tum oculis, velut ad O, P conſtitutis, apparebit ejuſce
              <lb/>
            duplex ſpecies α, _a_; </s>
            <s xml:id="echoid-s7282" xml:space="preserve">quarum illa (a) clauſo oculo O, hæc (_a_) clauſo
              <lb/>
            P diſparebit.</s>
            <s xml:id="echoid-s7283" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s7284" xml:space="preserve">Notetur autem, ſi placet, imaginum α, _a_ intervalla (pro vario
              <lb/>
            oculorum ſitu) nunc magìs, nunc minùs deduci, ſic ut ſubinde coadu-
              <lb/>
            nari videantur. </s>
            <s xml:id="echoid-s7285" xml:space="preserve">Nempe ſi oculus P ad F concipiatur tranſlatus, duca-
              <lb/>
            túrque FG ipſi PO parallela, & </s>
            <s xml:id="echoid-s7286" xml:space="preserve">æqualis; </s>
            <s xml:id="echoid-s7287" xml:space="preserve">unde jam & </s>
            <s xml:id="echoid-s7288" xml:space="preserve">oculus O
              <lb/>
            in C poſitus concipiatur; </s>
            <s xml:id="echoid-s7289" xml:space="preserve">quoniam FE minor eſt quàm FG, radius
              <lb/>
            MO per G non tranſibit; </s>
            <s xml:id="echoid-s7290" xml:space="preserve">tranſeat alter inflexus LG; </s>
            <s xml:id="echoid-s7291" xml:space="preserve">in hoc itaque
              <lb/>
            jam conſiſtet imago α, ab altera _a_; </s>
            <s xml:id="echoid-s7292" xml:space="preserve">magìs elongata. </s>
            <s xml:id="echoid-s7293" xml:space="preserve">Reliquarum hujuſ-
              <lb/>
            modi diverſitatum haud diſpar aſſignari poterit ratio.</s>
            <s xml:id="echoid-s7294" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s7295" xml:space="preserve">Adjungatur & </s>
            <s xml:id="echoid-s7296" xml:space="preserve">hoc, an paſſim obſervatum neſcio, dignum certè
              <lb/>
              <note position="right" xlink:label="note-0127-02" xlink:href="note-0127-02a" xml:space="preserve">Fig 179.</note>
            quod obſervetur: </s>
            <s xml:id="echoid-s7297" xml:space="preserve">Ad ſpeculum concavum RSMN faciem tuam
              <lb/>
            FAG (ſpeculo propiùs ad motam) contemplare. </s>
            <s xml:id="echoid-s7298" xml:space="preserve">Et primò quidem
              <lb/>
            oculo O (altero P occluſo) cernes ejus imaginem φαγ; </s>
            <s xml:id="echoid-s7299" xml:space="preserve">rurſus (ocu-
              <lb/>
            lo O occluſo) altero P conſpicies imaginem fag, à priore φαγ ali-
              <lb/>
            quantùm deflectentem; </s>
            <s xml:id="echoid-s7300" xml:space="preserve">demùm utroque ſimul oculo recluſo ſpectans
              <lb/>
            itlas in unam coalitas percipies; </s>
            <s xml:id="echoid-s7301" xml:space="preserve">ſeu, ſpeciem unam aſpicies, per-
              <lb/>
            quam notabili diſcrimine, ampliorem priorum ſingularum alterutrà.</s>
            <s xml:id="echoid-s7302" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s7303" xml:space="preserve">Exhinc, obiter, ſuſpicari licet, etiam intuitum ſimplicem adhiben-
              <lb/>
            tibus objecta binis oculis ſpectata tantillo majora videri, quàm uno;
              <lb/>
            </s>
            <s xml:id="echoid-s7304" xml:space="preserve">ſpeciebus ità coëuntibus, ut non exquiſitè congruant.</s>
            <s xml:id="echoid-s7305" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s7306" xml:space="preserve">Unicam prætereà ſubdemus inſtantiam: </s>
            <s xml:id="echoid-s7307" xml:space="preserve">Per ſphæram vitream (aut
              <lb/>
              <note position="right" xlink:label="note-0127-03" xlink:href="note-0127-03a" xml:space="preserve">Fig 180.</note>
            ſi mavis; </s>
            <s xml:id="echoid-s7308" xml:space="preserve">per phialam conicam aut cylindricam aquâ repletam) MBN
              <lb/>
            tranſlucentem lucernulæ flammam A ſpecta; </s>
            <s xml:id="echoid-s7309" xml:space="preserve">ejus duas imagines a, _a_;
              <lb/>
            </s>
            <s xml:id="echoid-s7310" xml:space="preserve">obſervabis (pro oculorum ſitu magìs à ſe minúſve diſſitas) quarum
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            una (a) clauſo oculo O, altera (_a_) clauſo P evaneſcet.</s>
            <s xml:id="echoid-s7311" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s7312" xml:space="preserve">Videtur hæc inſtantia vel ſola ſufficere vulgari ſententiæ refellendæ;
              <lb/>
            </s>
            <s xml:id="echoid-s7313" xml:space="preserve">
              <note position="right" xlink:label="note-0127-04" xlink:href="note-0127-04a" xml:space="preserve">_Paralipom. pag._
                <lb/>
              178.</note>
            juxta quam (ut _Keplerus_ alicubi colligit) puncti A ſimplex imago
              <lb/>
            ad punctum X conſiſteret.</s>
            <s xml:id="echoid-s7314" xml:space="preserve"/>
          </p>
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