Ibn-al-Haitam, al-Hasan Ibn-al-Hasan; Witelo; Risner, Friedrich, Opticae thesavrvs Alhazeni Arabis libri septem, nunc primùm editi. Eivsdem liber De Crepvscvlis & Nubium ascensionibus. Item Vitellonis Thuvringopoloni Libri X. Omnes instaurati, figuris illustrati & aucti, adiectis etiam in Alhazenum commentarijs, a Federico Risnero, 1572
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          <p>
            <s xml:id="echoid-s14094" xml:space="preserve">
              <pb o="203" file="0209" n="209" rhead="OPTICAE LIBER VI."/>
            uiſum à duobus punctis arcus:</s>
            <s xml:id="echoid-s14095" xml:space="preserve"> quod eſt impoſsibile [& contra 29 n 5.</s>
            <s xml:id="echoid-s14096" xml:space="preserve">] Licet autẽ reflectatur pun-
              <lb/>
            ctum illud à puncto primùm ſumpto:</s>
            <s xml:id="echoid-s14097" xml:space="preserve">
              <lb/>
              <figure xlink:label="fig-0209-01" xlink:href="fig-0209-01a" number="174">
                <variables xml:id="echoid-variables164" xml:space="preserve">d a b e h z g</variables>
              </figure>
              <figure xlink:label="fig-0209-02" xlink:href="fig-0209-02a" number="175">
                <variables xml:id="echoid-variables165" xml:space="preserve">a d b b g</variables>
              </figure>
            non tamen ũidetur, cum ſit in linea re
              <lb/>
            flexionis, quæ occultatur per præce-
              <lb/>
            dentia puncta.</s>
            <s xml:id="echoid-s14098" xml:space="preserve"> Et ita linea adiacens li-
              <lb/>
            neæ reflexionis non uidetur.</s>
            <s xml:id="echoid-s14099" xml:space="preserve"/>
          </p>
        </div>
        <div xml:id="echoid-div484" type="section" level="0" n="0">
          <head xml:id="echoid-head433" xml:space="preserve" style="it">20. Si uiſ{us} ſit in ſuperficie inci-
            <lb/>
          dentiæ: imago lineæ rectæ infinitæ,
            <lb/>
          peripheriam circuli (qui eſt commu-
            <lb/>
          nis ſectio ſuperficierũ reflexionis &
            <lb/>
          ſpeculi ſphærici conuexi) ſiue tangen
            <lb/>
          tis, ſiue non, & ad uiſ{us} partemobli-
            <lb/>
          quatæ, nulla uidebitur. 55 p 6.</head>
          <p>
            <s xml:id="echoid-s14100" xml:space="preserve">SI uerò ſumatur linea declinata,
              <lb/>
            cuius declinatio ſit ex parte ui-
              <lb/>
            ſus, iacẽs ſub linea reflexionis, &
              <lb/>
            ſecans ipſam in puncto circuli Dico,
              <lb/>
            quòd nullũ punctum illius lineæ uide
              <lb/>
            bitur.</s>
            <s xml:id="echoid-s14101" xml:space="preserve"> Sumpto enim pũcto:</s>
            <s xml:id="echoid-s14102" xml:space="preserve"> ſi dicatur,
              <lb/>
            quòd punctum illud poſsit reflecti ab
              <lb/>
            aliquo puncto arcus, interiacentis lineam reflexionis, & lineam à centro uiſus ad centrum ſpeculi
              <lb/>
            ductam:</s>
            <s xml:id="echoid-s14103" xml:space="preserve"> & ducatur linea ab illo puncto ad punctũ arcus ſumptum:</s>
            <s xml:id="echoid-s14104" xml:space="preserve"> hæc ſecabit lineam reflexionis:</s>
            <s xml:id="echoid-s14105" xml:space="preserve">
              <lb/>
            & punctum ſectionis reflectetur ad uiſum, à duobus punctis arcus ſpeculi:</s>
            <s xml:id="echoid-s14106" xml:space="preserve"> quod eſt impoſsibile [&
              <lb/>
            contra 29 n 5.</s>
            <s xml:id="echoid-s14107" xml:space="preserve">] Si uerò dicatur, quòd punctum ſumptum in linea, reflectatur à puncto arcus circuli,
              <lb/>
            qui eſt ſub ipſa linea:</s>
            <s xml:id="echoid-s14108" xml:space="preserve"> erit impoſsibile:</s>
            <s xml:id="echoid-s14109" xml:space="preserve"> quia ille totus arcus occultatur à linea.</s>
            <s xml:id="echoid-s14110" xml:space="preserve"/>
          </p>
        </div>
        <div xml:id="echoid-div485" type="section" level="0" n="0">
          <head xml:id="echoid-head434" xml:space="preserve" style="it">21. Si uiſ{us} ſit in ſuperficie incidentiæ: ιmago lιneæ rectæ infinitæ; peripheriam circuli (qui
            <lb/>
          eſt communis ſectio ſuperficierum, reflexionis & ſpeculi ſphærici conuexi) nec tangentis nec per
            <lb/>
          centrum ſecantis, & ad partem uιſuι oppoſitam obliquatæ, uidebitur curua. 56 p 6.</head>
          <p>
            <s xml:id="echoid-s14111" xml:space="preserve">SI uerò linea ſumpta nõ attingat circulum:</s>
            <s xml:id="echoid-s14112" xml:space="preserve"> poterit quidem uideri:</s>
            <s xml:id="echoid-s14113" xml:space="preserve"> ſed modicum eſt.</s>
            <s xml:id="echoid-s14114" xml:space="preserve"> Si uerò ſu-
              <lb/>
            matur linea declinata prædicta inter lineam reflexionis, & lineam per punctũ reflexionis pri-
              <lb/>
            mò ſumptum tranſeuntem ad centrum:</s>
            <s xml:id="echoid-s14115" xml:space="preserve"> poterit quidem uideri hæclinea:</s>
            <s xml:id="echoid-s14116" xml:space="preserve"> & imminuetur cur-
              <lb/>
            uitas imaginis huius lineæ, ſecundum quod magis acceſſerit ad lineã tranſeuntem ad centrum, per
              <lb/>
            punctum reflexionis.</s>
            <s xml:id="echoid-s14117" xml:space="preserve"> Si uerò ſumantur lineæ inter lineam ad centrũ
              <lb/>
              <figure xlink:label="fig-0209-03" xlink:href="fig-0209-03a" number="176">
                <variables xml:id="echoid-variables166" xml:space="preserve">a d f b ſ m e
                  <gap/>
                c z g</variables>
              </figure>
            tranſeuntem per punctum reflexionis:</s>
            <s xml:id="echoid-s14118" xml:space="preserve"> uidebuntur quidem, ſiue de-
              <lb/>
            clinatio earum ſit ex parte uiſus, ſiue non:</s>
            <s xml:id="echoid-s14119" xml:space="preserve"> & modus uiſus earũ, ſimi-
              <lb/>
            lis modo uiſus linearum inter lineam reflexionis & lineam ad cen-
              <lb/>
            trum tranſeuntem.</s>
            <s xml:id="echoid-s14120" xml:space="preserve"> Et hæc quidem intelligenda ſunt de lineis con-
              <lb/>
            currentibus in arcu circuli, qui apparet uiſui, id eſt, in arcu, qui inter-
              <lb/>
            iacet duas contingentes, ductas à centro uiſus ad circulum.</s>
            <s xml:id="echoid-s14121" xml:space="preserve"> Linearũ
              <lb/>
            autem concurrentium cum circulo in parte circuli occulta uiſui:</s>
            <s xml:id="echoid-s14122" xml:space="preserve"> ali-
              <lb/>
            qua erit æquidiſtans lineæ reflexionis:</s>
            <s xml:id="echoid-s14123" xml:space="preserve"> & illa quidem non uidebitur.</s>
            <s xml:id="echoid-s14124" xml:space="preserve">
              <lb/>
            Similiter conterminalis æquidiſtanti, quæ eſt ſub æquidiſtante, oc-
              <lb/>
            cultabitur:</s>
            <s xml:id="echoid-s14125" xml:space="preserve"> ſed conterminalis æquidiſtanti, ſupra ipſam exiſtens, po-
              <lb/>
            terit uideri.</s>
            <s xml:id="echoid-s14126" xml:space="preserve"> Si uerò ſumatur linea inter æquidiſtantes, nõ contermi-
              <lb/>
            nalis alicui earum:</s>
            <s xml:id="echoid-s14127" xml:space="preserve"> ſi fuerit eius declinatio ex parte uiſus, uidebitur:</s>
            <s xml:id="echoid-s14128" xml:space="preserve">
              <lb/>
            ſi ex alia parte, aliquando uidebitur, aliquãdo non Quoniam ſi à ter-
              <lb/>
            mino eius ducatur æquidiſtans lineæ reflexionis:</s>
            <s xml:id="echoid-s14129" xml:space="preserve"> ſi fuerit linea ſub
              <lb/>
            æquidiſtante:</s>
            <s xml:id="echoid-s14130" xml:space="preserve"> non uidebitur:</s>
            <s xml:id="echoid-s14131" xml:space="preserve"> ſi ſupra eã, uideri poterit.</s>
            <s xml:id="echoid-s14132" xml:space="preserve"> Si uerò lineæ
              <lb/>
            non concurrant cum circulo, aut ſecabunt lineam ductam à centro
              <lb/>
            uiſus ad cẽtrum ſpeculi:</s>
            <s xml:id="echoid-s14133" xml:space="preserve"> aut æquidiſtabunt ei.</s>
            <s xml:id="echoid-s14134" xml:space="preserve"> Si ſecet aliqua earum:</s>
            <s xml:id="echoid-s14135" xml:space="preserve">
              <lb/>
            linea illa aut ſecabit illam ex parte uiſus, id eſt, inter uiſum & ſpecu-
              <lb/>
            lum:</s>
            <s xml:id="echoid-s14136" xml:space="preserve"> aut ultra ſpeculũ.</s>
            <s xml:id="echoid-s14137" xml:space="preserve"> Si ultra:</s>
            <s xml:id="echoid-s14138" xml:space="preserve"> occultabitur linea illa, ſed forſan ap-
              <lb/>
            parebunt eius capita.</s>
            <s xml:id="echoid-s14139" xml:space="preserve"> Si uerò ſecet lineam uiſualem ex parte uiſus, apparebit quidem ſimiliter.</s>
            <s xml:id="echoid-s14140" xml:space="preserve"> Si
              <lb/>
            fuerit æquidιſtans lineæ uiſuali:</s>
            <s xml:id="echoid-s14141" xml:space="preserve"> poterit uideri.</s>
            <s xml:id="echoid-s14142" xml:space="preserve"> Omnium autem harum linearum imagines curuæ.</s>
            <s xml:id="echoid-s14143" xml:space="preserve">
              <lb/>
            Vιſu autem exiſtente in eadem ſuperficie cum centro ſpeculi & lineis uiſis, diminuta eſt apparẽtia:</s>
            <s xml:id="echoid-s14144" xml:space="preserve">
              <lb/>
            & quæ ſit, quæ manifeſtius apparet, eſt illa, quæ declinata eſt maxima declinatione, & illa uiſum re-
              <lb/>
            ſpiciente.</s>
            <s xml:id="echoid-s14145" xml:space="preserve"> Pari modo arcuum in his ſpeculis apparentium, & in eadem ſuperficie cum cẽtro ſpecu-
              <lb/>
            li, & uiſu exiſtẽtium, imagines quidẽ curuæ ſunt curuitate ſpeculũ reſpiciente.</s>
            <s xml:id="echoid-s14146" xml:space="preserve"> Hæc aũt intelligẽda
              <lb/>
            ſunt duplici uiſu exiſtẽte in eadẽ ſuperficie cũ cẽtro ſpeculi, & re uiſa.</s>
            <s xml:id="echoid-s14147" xml:space="preserve"> Si enim alter uiſus modicùm
              <lb/>
            declinetur, quò ad ipſum, alio modo res uiſa comprehendetur.</s>
            <s xml:id="echoid-s14148" xml:space="preserve"> Et uiſu exiſtente extra ſuperficiem
              <lb/>
            rei uiſæ & centrum ſpeculi, certior erit ipſius rei comprehenſio, quam exiſtente in ea.</s>
            <s xml:id="echoid-s14149" xml:space="preserve"/>
          </p>
        </div>
        <div xml:id="echoid-div487" type="section" level="0" n="0">
          <head xml:id="echoid-head435" xml:space="preserve" style="it">22. Si uiſ{us} ſit in ſuperficie incidentiæ: imago lineæ rectæ infinitæ, quæ uel non concurrens
            <lb/>
          </head>
        </div>
      </text>
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