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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          <pb o="253" file="0259" n="259" rhead="OPTICAE LIBER VII."/>
        </div>
        <div xml:id="echoid-div576" type="section" level="0" n="0">
          <head xml:id="echoid-head499" xml:space="preserve">DE IMAGINIBVS. CAP. V.</head>
          <head xml:id="echoid-head500" xml:space="preserve" style="it">17. Imago (quæ eſt forma refracti uiſibilis à medio diuerſo) extra uiſibilis locum uidetur.
            <lb/>
          in defin. 11 p 10.</head>
          <p>
            <s xml:id="echoid-s17663" xml:space="preserve">IMago eſt forma rei uiſibilis, quam uiſus comprehendit ultra diaphanum corpus, quod differt in
              <lb/>
            ſua diaphanitate à diaphanitate aeris, cum uiſus fuerit obliquus à perpendicular b.</s>
            <s xml:id="echoid-s17664" xml:space="preserve"> exeuntib.</s>
            <s xml:id="echoid-s17665" xml:space="preserve"> ab
              <lb/>
            illo uiſibili ad ſuperficiem illius corporis diaphani.</s>
            <s xml:id="echoid-s17666" xml:space="preserve"> Nam forma, quam cõprehendit uiſus in cor-
              <lb/>
            pore diaphano de re uiſa, quæ eſt ultra ipſum corpus, non eſt ipſa res uiſa:</s>
            <s xml:id="echoid-s17667" xml:space="preserve"> quoniam uiſus tunc non
              <lb/>
            comprehendit rem uiſam in ſuo loco, neque in ſua forma, ſed in alio loco & in alio modo, ſcilicet re
              <lb/>
            fracte:</s>
            <s xml:id="echoid-s17668" xml:space="preserve"> & cum hoc comprehendit illam rem in ſua oppoſitione:</s>
            <s xml:id="echoid-s17669" xml:space="preserve"> hęc autem forma dicitur imago.</s>
            <s xml:id="echoid-s17670" xml:space="preserve"> Hoc
              <lb/>
            autem comprehenditur ratione & experientia.</s>
            <s xml:id="echoid-s17671" xml:space="preserve"> Ratione, quoniam ex prędicto capitulo patet, quòd
              <lb/>
            uiſum, quod eſt in diaphano corpore diuerſę diaphanitatis ab aere, comprehenditur à uiſu refractè,
              <lb/>
            cum uiſus fuerit decliuis à perpendicularib.</s>
            <s xml:id="echoid-s17672" xml:space="preserve"> exeuntibus à re uiſa ſuper ſuperficiem corporis diapha
              <lb/>
            ni.</s>
            <s xml:id="echoid-s17673" xml:space="preserve"> Et cum uiſus comprehendit huiuſmodi uiſum refractè, nec eſt in oppoſitione eius, non cõprehẽ
              <lb/>
            dit ipſum rectè, nec ſentit ſe comprehẽdere ipſum refractè:</s>
            <s xml:id="echoid-s17674" xml:space="preserve"> patet, quòd comprehendit ipſum extra
              <lb/>
            ſuum locum.</s>
            <s xml:id="echoid-s17675" xml:space="preserve"> Per experientiam uero ſic poteſt cognoſci.</s>
            <s xml:id="echoid-s17676" xml:space="preserve"> Nam ſi aliquis acceperit uas habens oras
              <lb/>
            erectas perpendiculares, in cuius medio poſuerit aliquod uiſum manifeſtum, ut obolum aut dena-
              <lb/>
            rium, & ſteterit à longè, quouſq;</s>
            <s xml:id="echoid-s17677" xml:space="preserve"> uiderit rem uiſam in profundo uaſis:</s>
            <s xml:id="echoid-s17678" xml:space="preserve"> deinde elongauerit ſe à re ui-
              <lb/>
            ſa, quouſque non uideat rem paulatim:</s>
            <s xml:id="echoid-s17679" xml:space="preserve"> tunc in initio occultationis ſtet in ſuo loco, & præcipiat alte
              <lb/>
            ri infundere aquam in uas ipſo exiſtente in ſuo loco, nec moueat uiſum, nec mutet ſitum:</s>
            <s xml:id="echoid-s17680" xml:space="preserve"> tunc enim
              <lb/>
            cum aſpexerit aquam, quæ eſt in uaſe:</s>
            <s xml:id="echoid-s17681" xml:space="preserve"> uidebit rem uiſam, poſtquam non uiderat eam, & uidebit eã
              <lb/>
            in eius oppoſitione.</s>
            <s xml:id="echoid-s17682" xml:space="preserve"> Ex quo patet, quòd forma, quam uidet in aqua, nõ eſt in loco uiſi.</s>
            <s xml:id="echoid-s17683" xml:space="preserve"> Nam ſi forma
              <lb/>
            eſſet in loco uiſi:</s>
            <s xml:id="echoid-s17684" xml:space="preserve"> tunc uiſus comprehẽderet rem uiſam non exiſtente aqua in uaſe:</s>
            <s xml:id="echoid-s17685" xml:space="preserve"> uiſus enim in ſe-
              <lb/>
            cundo ſtatu comprehendit rem uiſam in ſua oppoſitione, ipſa non exiſtẽte in ſua oppoſitione.</s>
            <s xml:id="echoid-s17686" xml:space="preserve"> Hoc
              <lb/>
            ergo modo declarabitur utroque modo, ratione uidelicet & experientia, quòd imago rei uiſæ, quã
              <lb/>
            uiſus comprehendit refractè, non eſt in loco rei uiſæ.</s>
            <s xml:id="echoid-s17687" xml:space="preserve"/>
          </p>
        </div>
        <div xml:id="echoid-div577" type="section" level="0" n="0">
          <head xml:id="echoid-head501" xml:space="preserve" style="it">18. Imago uideturin concurſu linearum refractionis, & perpendicularis incidentiæ. 15 p 10.</head>
          <p>
            <s xml:id="echoid-s17688" xml:space="preserve">DEinde dico, quòd imago cuiuslibet puncti, quod uiſus comprehendit refractè, eſt in puncto,
              <lb/>
            quod eſt differentia communis lineæ, per quam forma peruenit ad uiſum, & perpendicula-
              <lb/>
            ri, exeunti ab illo puncto uiſo ſuper ſuperficiem diaphani corporis.</s>
            <s xml:id="echoid-s17689" xml:space="preserve"> Hoc autem declarabitur
              <lb/>
            per experientiam hoc modo.</s>
            <s xml:id="echoid-s17690" xml:space="preserve"> Accipiat aliquis circulum ligneum, cuius diam eter non ſit minor uno
              <lb/>
            cubito, altitudo duorum ueltrium digitorum, & adęquet ſuperficies eius quantumcunque poterit:</s>
            <s xml:id="echoid-s17691" xml:space="preserve">
              <lb/>
            & inueniat centrum eius, & extrahat in ipſo diametros ſeſe interſecantes quomodocunque uolue-
              <lb/>
            rit, & ſignentur ferro, ut appareant, & impleat lineas illas corpore albo, ut ceruſa mixta lacte:</s>
            <s xml:id="echoid-s17692" xml:space="preserve"> & pun
              <lb/>
            ctum centri ſit nigrum.</s>
            <s xml:id="echoid-s17693" xml:space="preserve"> Hoc autem perfecto, accipiat uas amplum, ut peluim habens oras eleuatas,
              <lb/>
            & ponat uas in loco luminoſo, & infundat in uas aquam claram, & ſit altitudo aquæ minor diame-
              <lb/>
            tro circuli, & maior ſemidiam etro eius, & menſuretur hoc ipſo circulo, quouſque aqua tranſeat cen
              <lb/>
            trum circuli aliquot digitis, duabus ſcilicet diametris aut pluribus ſignatis in ipſo uaſe, ſcilicet, ut
              <lb/>
            ſit aqua cooperiens aliquam partem utriuſque diametri, & remaneat altera pars extra aquã, & ex-
              <lb/>
            pectet, donec aqua quieſcat in uaſe, & tunc mittat circulum ligneum in uas, & erigat circulum ſu-
              <lb/>
            per oram ipſius, & ponat ſuperficiem ipſius, in qua ſunt lineæ ſignatæ, ex parte uiſus:</s>
            <s xml:id="echoid-s17694" xml:space="preserve"> deinde moue-
              <lb/>
            at circulum, donec aliqua ſuarum diametrorum ſit perpendicularis ſuper ſuperficiem aquæ:</s>
            <s xml:id="echoid-s17695" xml:space="preserve"> dein-
              <lb/>
            de dimittat uiſum ſuum, & erigat uas, quouſque uiſus ſimul appropinquet æquidiſtantiæ ſuperfi-
              <lb/>
            ciei aquæ, & extra oram uaſis, & ſupra ſuperficiem aquæ in tantùm, ut poſsit uidere centrum circu-
              <lb/>
            li:</s>
            <s xml:id="echoid-s17696" xml:space="preserve"> experientia enim ſecundum hunc modum erit manifeſtior.</s>
            <s xml:id="echoid-s17697" xml:space="preserve"> Hoc ergo facto, intueatur centrũ cir-
              <lb/>
            culi & diametrum circuli perpendicularem ſuper ſuperficiem aquæ:</s>
            <s xml:id="echoid-s17698" xml:space="preserve"> tunc enim inueniet centrum
              <lb/>
            circuli in rectitudine diame
              <gap/>
            ri perpendicularis.</s>
            <s xml:id="echoid-s17699" xml:space="preserve"> Deιnde intueatur diametrum circuli decliuem, cu-
              <lb/>
            ius pars eminet ſupra aquam:</s>
            <s xml:id="echoid-s17700" xml:space="preserve"> tunc enim inueniet ipſam incuruatam:</s>
            <s xml:id="echoid-s17701" xml:space="preserve"> cuius incuruatio erit apud ſu-
              <lb/>
            perficiem aquæ:</s>
            <s xml:id="echoid-s17702" xml:space="preserve"> & illa pars, quæ eſt intra aquam, continet cum illa, quæ eſt extra aquam, angulum
              <lb/>
            obtuſum:</s>
            <s xml:id="echoid-s17703" xml:space="preserve"> & inueniet angulum ex parte diametri perpendicularis:</s>
            <s xml:id="echoid-s17704" xml:space="preserve"> & inueniet illud, quod eſt intra
              <lb/>
            aquam, rectum & continuum.</s>
            <s xml:id="echoid-s17705" xml:space="preserve"> Ex quo patet, quòd forma puncti, quod eſt centrum circuli, ſcilicet
              <lb/>
            forma, quam uiſus comprehendit, non eſt apud centrum circuli.</s>
            <s xml:id="echoid-s17706" xml:space="preserve"> Nam ſi eſſet apud centrum circu-
              <lb/>
            li:</s>
            <s xml:id="echoid-s17707" xml:space="preserve"> tunc eſſet in rectitudine diametri decliu
              <gap/>
            s:</s>
            <s xml:id="echoid-s17708" xml:space="preserve"> nam in rei ueritate talem habet ſitum.</s>
            <s xml:id="echoid-s17709" xml:space="preserve"> Cum ergo uiſus
              <lb/>
            comprehendit hoc punctum extra rectitudinem diametri decliuis, & anguli, quem continent par-
              <lb/>
            tes diametri decliuis, ſequuntur diametrum perpendicularem:</s>
            <s xml:id="echoid-s17710" xml:space="preserve"> tunc punctum, quod eſt forma cen-
              <lb/>
            tri, eſt eleuatum à centro.</s>
            <s xml:id="echoid-s17711" xml:space="preserve"> Et quia uiſus comprehendit hoc punctum in rectitudine diametri, per-
              <lb/>
            pendicularis ſuper ſuperficiem aquæ:</s>
            <s xml:id="echoid-s17712" xml:space="preserve"> erit hoc punctum, quod eſt forma puncti, quod eſt in centro,
              <lb/>
            eleuatum à centro:</s>
            <s xml:id="echoid-s17713" xml:space="preserve"> & cum hoc, eſt in rectitudine perpendicularis, exeuntis à centro ſuper ſuperfi-
              <lb/>
            ciem aquæ.</s>
            <s xml:id="echoid-s17714" xml:space="preserve"> Et declarabitur ex incuruatione diametri decliuis apud ſuperficiem aquæ, & rectitu-
              <lb/>
            dine eius, quod eſt ntra aquam ex diametro, & continuatione eius:</s>
            <s xml:id="echoid-s17715" xml:space="preserve"> quòd omne punctum partis,
              <lb/>
            quæ eſt intra aquã ex diametro decliui, eſt eleuatum à ſuo loco.</s>
            <s xml:id="echoid-s17716" xml:space="preserve"> Deinde oportet experimẽtatorem
              <lb/>
            reuoluere cιrculum ligneum, quouſque diameter decliuis fiat perpendicularis ſuper ſuperficiem
              <lb/>
            </s>
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