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-s5511" xml:space="preserve">
              <pb o="85" file="0103" n="103" rhead=""/>
            KIZ- CKZ = ang NZI- 2 ang CKZ = 2 ang NZ C-
              <lb/>
            2 ang CKZ = 2 ang. </s>
            <s xml:id="echoid-s5512" xml:space="preserve">ZCD = ZC Y. </s>
            <s xml:id="echoid-s5513" xml:space="preserve">eſt igitur ang. </s>
            <s xml:id="echoid-s5514" xml:space="preserve">OFL =
              <lb/>
            ang ZC Y. </s>
            <s xml:id="echoid-s5515" xml:space="preserve">Cùm itaque ſit in ſuperiore Hypotheſi punctum Z um-
              <lb/>
            bræ lucíſque confinium, manifeſtè liquet propoſitum.</s>
            <s xml:id="echoid-s5516" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s5517" xml:space="preserve">XV. </s>
            <s xml:id="echoid-s5518" xml:space="preserve">Subnotetur autem, ſi medium inflectens ſit aqueum, arcum
              <lb/>
            ZY eſſe partem circuli totam (poſticam ſcilicet) illuminatam; </s>
            <s xml:id="echoid-s5519" xml:space="preserve">tan-
              <lb/>
            gentis enim ST refractus, puta TV, nedum non punctum Y præ-
              <lb/>
            tergreditur, at citra punctum D cadit. </s>
            <s xml:id="echoid-s5520" xml:space="preserve">aſt in denſioribus mediis, ve-
              <lb/>
            lut in vitro, ſecùs accidere poteſt; </s>
            <s xml:id="echoid-s5521" xml:space="preserve">ſiquidem in eo tangentis refractus,
              <lb/>
              <note position="right" xlink:label="note-0103-01" xlink:href="note-0103-01a" xml:space="preserve">Fig. 128.</note>
            puta TX, ultra terminum Y (modo prædicto deſignatum) cadit,
              <lb/>
            ut quidem ex calculo facilè colligatur; </s>
            <s xml:id="echoid-s5522" xml:space="preserve">unde pars illuminata arcu ZY
              <lb/>
            amplior evadit; </s>
            <s xml:id="echoid-s5523" xml:space="preserve">tangentium quippe refractis circumſcripta. </s>
            <s xml:id="echoid-s5524" xml:space="preserve">Vide-
              <lb/>
            rit igitur excellentiſſimus vir; </s>
            <s xml:id="echoid-s5525" xml:space="preserve">an univerſim conftet (id quod ipſe
              <lb/>
            niſi fallor innuere videbatur) ex obſervata partis illuminatæ quantitate,
              <lb/>
            _Iridis angulam, etiam juxta Carteſianas Hypotbeſes, recte determi-_
              <lb/>
            _nari._ </s>
            <s xml:id="echoid-s5526" xml:space="preserve">Nam ſumendo arcum DR = DX; </s>
            <s xml:id="echoid-s5527" xml:space="preserve">ad punctum quidem R
              <lb/>
            pertinget illuſtratio; </s>
            <s xml:id="echoid-s5528" xml:space="preserve">neque tamen ulla lux quadranti BT incidens à
              <lb/>
            parte ZR (ſed illa tantùm quæ ad partes ZD cadit) ad oculum O
              <lb/>
            inflectetur. </s>
            <s xml:id="echoid-s5529" xml:space="preserve">unde quoad oculos ad has partes ſitos, hoc eſt quoad rem
              <lb/>
            quæ præ manibus, punctum Z lucem & </s>
            <s xml:id="echoid-s5530" xml:space="preserve">umbram dirimit atque diſter-
              <lb/>
            minat.</s>
            <s xml:id="echoid-s5531" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s5532" xml:space="preserve">XVI. </s>
            <s xml:id="echoid-s5533" xml:space="preserve">Vobis autem expendendum propono, annon exhinc _appa-_
              <lb/>
              <note position="right" xlink:label="note-0103-02" xlink:href="note-0103-02a" xml:space="preserve">Fig. 128.</note>
            _rentiarum in Iride ratio_ elici poſſit, illâ fortè veriſimi ior, quam
              <lb/>
            ipſe _Carteſius_ aſſignavit. </s>
            <s xml:id="echoid-s5534" xml:space="preserve">quid enim ſi dixero peripheriæ ZV impin-
              <lb/>
            gentem lucem, & </s>
            <s xml:id="echoid-s5535" xml:space="preserve">verſus O inflexam magìs apparere; </s>
            <s xml:id="echoid-s5536" xml:space="preserve">primò, quia ſpiſ-
              <lb/>
            ſior eſt, ac à radiorum geminâ diffuſione conſtat, ab utraque puncti N
              <lb/>
            parte in arcum ZV retractorum; </s>
            <s xml:id="echoid-s5537" xml:space="preserve">tum ſecundò quoniam obliquius
              <lb/>
            ipſi ZV incidit, adeóque faciliùs & </s>
            <s xml:id="echoid-s5538" xml:space="preserve">copioſiùs indè quam aliunde
              <lb/>
            verſus partes O retorquetur? </s>
            <s xml:id="echoid-s5539" xml:space="preserve">Et cum præſertim circa punctum Z
              <lb/>
            acutiùs radii coëant, neque non incurrant obliquius; </s>
            <s xml:id="echoid-s5540" xml:space="preserve">quidni proptereà
              <lb/>
            vividier exindè reſultet apparentia? </s>
            <s xml:id="echoid-s5541" xml:space="preserve">Verùm hæc παρβακῶ
              <unsure/>
            ς.</s>
            <s xml:id="echoid-s5542" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s5543" xml:space="preserve">_Quoniam Colorum incidit mentio, quid ſi de illis_ (etſi præter morem
              <lb/>
            ac ordinem) paucula divinavero?</s>
            <s xml:id="echoid-s5544" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s5545" xml:space="preserve">XVII. </s>
            <s xml:id="echoid-s5546" xml:space="preserve">_Album_ eſt quod lucem copioſam, pariter ubique ſpiſſam,
              <lb/>
            circumfundit. </s>
            <s xml:id="echoid-s5547" xml:space="preserve">Talia fermè ſunt corpora, rarioribus poris inter-
              <lb/>
            puncta; </s>
            <s xml:id="echoid-s5548" xml:space="preserve">præſertim, quæ multas ſuperficieculas, in omne latus obver-
              <lb/>
            ſas, habent. </s>
            <s xml:id="echoid-s5549" xml:space="preserve">Suadetur hoc, Quia purè lucida ſemper alba videntur;</s>
            <s xml:id="echoid-s5550" xml:space="preserve"/>
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