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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        <div xml:id="echoid-div635" type="section" level="0" n="0">
          <head xml:id="echoid-head542" xml:space="preserve">ALHAZEN FILII</head>
          <head xml:id="echoid-head543" xml:space="preserve">ALHAYZEN DE CREPVSCVLIS</head>
          <head xml:id="echoid-head544" xml:space="preserve">ET NVBIVM ASCENSIONIBVS LIBER VNVS.</head>
          <head xml:id="echoid-head545" xml:space="preserve">Gerardo Cremonenſi interprete.</head>
          <head xml:id="echoid-head546" xml:space="preserve" style="it">NVMERI.</head>
          <head xml:id="echoid-head547" xml:space="preserve" style="it">1. Crepuſculum matutinum incipit, ac ueſpertinum deſinit, ſole ante ortum & poſt occaſum
            <lb/>
          ſuum 19 partib{us}, in peripheria circuli per uerticem regionis ſolis́ locum tranſeuntis, ſub
            <lb/>
          horizontem demerſo.</head>
          <p>
            <s xml:id="echoid-s19662" xml:space="preserve">OStendere uolo in hoc tractatu quid ſit crepuſculum, & quæ cauſſa neceſſariò faciens
              <lb/>
            eius apparitionem:</s>
            <s xml:id="echoid-s19663" xml:space="preserve"> inde uerò progrediar ad cognoſcendum ultimum, quod eleuatur
              <lb/>
            à ſuperficie terræ, de uaporibus ſubtilibus aſcendentibus ex ea.</s>
            <s xml:id="echoid-s19664" xml:space="preserve"> Dico ergo, quòd cre-
              <lb/>
            puſculum matutinum & crepuſculum ueſpertinum ſunt ſimilis figuræ:</s>
            <s xml:id="echoid-s19665" xml:space="preserve"> unum namq;</s>
            <s xml:id="echoid-s19666" xml:space="preserve">
              <lb/>
            eorum ex acceſsione luminis ſolis, & alterũ ex ipſius receſsione contingit.</s>
            <s xml:id="echoid-s19667" xml:space="preserve"> Vtrorumq;</s>
            <s xml:id="echoid-s19668" xml:space="preserve">
              <lb/>
            uerò colorẽs diuerſi ſunt, propter diuerſitatem horizontum;</s>
            <s xml:id="echoid-s19669" xml:space="preserve"> in quibus ſol eſt apparens.</s>
            <s xml:id="echoid-s19670" xml:space="preserve"> Quoniam
              <lb/>
            ſol quando eſt in horizonte orientali, non multum eleuatus, eſt illic color eius alius à colore ipſius
              <lb/>
            in uiſibus, quando eſt ſecundum æqualitatem illius altitudinis in horizonte occidentall.</s>
            <s xml:id="echoid-s19671" xml:space="preserve"> Et ſimili-
              <lb/>
            ter radij eius, qui uidẽtur in crepuſculo, & quod uidetur in æthere de luminibus eius.</s>
            <s xml:id="echoid-s19672" xml:space="preserve"> Et ipſe æther
              <lb/>
            coloratus eſt, ſequens illud, ſecundum quod eſt ſol in utriſque partibus eius.</s>
            <s xml:id="echoid-s19673" xml:space="preserve"> Nam qui ex illo eſt in
              <lb/>
            oriente color, eſt albedo & claritas:</s>
            <s xml:id="echoid-s19674" xml:space="preserve"> & qui eſt in occidẽte, ad rubedinem aliquantulùm uergit.</s>
            <s xml:id="echoid-s19675" xml:space="preserve"> Quæ
              <lb/>
            res uerò ſit illud illuminans, & qualiter ſit apparens illic, & quæ cauſſa neceſſariò faciat ipſum, ad il-
              <lb/>
            lud præmittemus propoſitiones, exponentes illud, cuius uolumus declarationem.</s>
            <s xml:id="echoid-s19676" xml:space="preserve"> Ex illo quidem
              <lb/>
            eſt, quòd ſphæra orbis [è terra & aqua conſtantis] tota ſemper eſt ſplendida & luminoſa ex lumi-
              <lb/>
            nari maiori (quod eſt ſol) niſi quantum obtegunt tenebræ contingẽtes ex terra, in figura pyrami-
              <lb/>
            dis, quæ eſt nox.</s>
            <s xml:id="echoid-s19677" xml:space="preserve"> Et ego non ſignifico in hoc libro per illud, quod accidit de huiuſmodi receptionè
              <lb/>
            luminis ex ſphæris ſtellarum, niſi quòd cum ſphæra, propter claritatem aeris & ſubtilitatem æthe-
              <lb/>
            ris, & tenuitatem eius non ſuſpenditur aliquid de lumine ſolis, ſicut uidemus ipſum ſuſpendi cum
              <lb/>
            corporibus altis (quę ſunt ſtellæ) quia illuminantur & deferunt nobis illud, quod recipiunt exlu-
              <lb/>
            mine, & conſequuntur ipſum uiſus noſtri in eis:</s>
            <s xml:id="echoid-s19678" xml:space="preserve"> & quamuis diſſentiant in ſtellis, in lumine tamen
              <lb/>
            non diſſentiunt.</s>
            <s xml:id="echoid-s19679" xml:space="preserve"> Viſus autem noſtri non conſequũtur, quod in eis eſt de luminibus:</s>
            <s xml:id="echoid-s19680" xml:space="preserve"> niſi quòd ipſæ
              <lb/>
            procul dubio ſunt ſpiſsioris & uehementioris corporeitatis;</s>
            <s xml:id="echoid-s19681" xml:space="preserve"> quàm æther, in quo ſunt.</s>
            <s xml:id="echoid-s19682" xml:space="preserve"> Et hoc patet
              <lb/>
            per ſignificationes, quòd quædam earum tegunt nobis quaſdam, quia eclipſant eas:</s>
            <s xml:id="echoid-s19683" xml:space="preserve"> aer uerò non
              <lb/>
            tegit nobis aliquid ex eis, quæ ſunt poſt ipſum.</s>
            <s xml:id="echoid-s19684" xml:space="preserve"> Et propterea uidemus, quòd tota nox eſt ſecundum
              <lb/>
            habitudinem unam, in qua non illuminatur nobis ex æthere aliquid:</s>
            <s xml:id="echoid-s19685" xml:space="preserve"> quamuis ſciamus ſecundum
              <lb/>
            ſcientiam noſtram, quòd quàmplurimum eius ætheris eſt luminoſum, non tectum à ſole.</s>
            <s xml:id="echoid-s19686" xml:space="preserve"> Et uide-
              <lb/>
            mus quòd illud, quod ex eo ſoli apparet, & nihil aliud tegit, eſt in uiſione, ſicut illud, quod terra te-
              <lb/>
            git, quod pyramis tenebrarum continet.</s>
            <s xml:id="echoid-s19687" xml:space="preserve"> Et non facit neceſſariò æqualitatem utriuſq;</s>
            <s xml:id="echoid-s19688" xml:space="preserve"> apud uiſus
              <lb/>
            noſtros, niſi illud, quod diximus de ſubtilitate aeris, & quòd non perducit illuminationem eius, &
              <lb/>
            perducit nobis tenebroſitatem ipſius.</s>
            <s xml:id="echoid-s19689" xml:space="preserve"> Tunc autem non ceſſat habitudo umbræ apparere nobis ſe-
              <lb/>
            cundum ſimilitudinem ipſius, quouſq;</s>
            <s xml:id="echoid-s19690" xml:space="preserve"> incipiat ab oriente ſplendor diluculi & lumen ſparſum, cu-
              <lb/>
            ius principium eſt in primis cum ſuperficie horizontis:</s>
            <s xml:id="echoid-s19691" xml:space="preserve"> & illius principij non eſt nobis cauffa, niſi
              <lb/>
            ſol:</s>
            <s xml:id="echoid-s19692" xml:space="preserve"> cum ſit cauſſa illuminationũ.</s>
            <s xml:id="echoid-s19693" xml:space="preserve"> Et non eſt nobis principium illud ſol ipſe, nec radius eius tantùm,
              <lb/>
            quoniam iam præmiſimus, quòd radij eius pertranſeunt uſq;</s>
            <s xml:id="echoid-s19694" xml:space="preserve"> ad ætherem totum, quem uidemus,
              <lb/>
            aut ad plurimum eius:</s>
            <s xml:id="echoid-s19695" xml:space="preserve"> & nõ eſt diuerſa eius habitudo in illa hora ab alia habitudine ante illud.</s>
            <s xml:id="echoid-s19696" xml:space="preserve"> Ve-
              <lb/>
            runtamen radij eius ſuſpenduntur tunc cum aliquo corpore ſpiſsiore aere:</s>
            <s xml:id="echoid-s19697" xml:space="preserve"> ducit ergo nobis cum
              <lb/>
            ſua ſpiſsitudine radium, quem induit.</s>
            <s xml:id="echoid-s19698" xml:space="preserve"> Et dico, quòd illud, quo ſuſpenſus eſt radius in illa hora, non
              <lb/>
            eſt terra, neq;</s>
            <s xml:id="echoid-s19699" xml:space="preserve"> extremitates plagarum eius diſtinctæ à nobis:</s>
            <s xml:id="echoid-s19700" xml:space="preserve"> quoniam cum uidens eſt ſuper æqua-
              <lb/>
            litatem terræ, non peruenit eius uiſus, niſi quaſi ad 23 milliaria [Italica] ab omni parte.</s>
            <s xml:id="echoid-s19701" xml:space="preserve"> Et ſi acci-
              <lb/>
            dit ei, ut ſit ſuper altiorem montium, qui eſſe poteſt (& ille non pertranſit octo milliaria, ſecundum
              <lb/>
            quod dixerunt ſapientes, intendentes hoc) uiſus non pertranſit tunc, niſi 250 milliaria ferè.</s>
            <s xml:id="echoid-s19702" xml:space="preserve"> Et hoc
              <lb/>
            manifeſtum eſt ex eo, quòd noctẽ facit forma terræ:</s>
            <s xml:id="echoid-s19703" xml:space="preserve"> ſed altitudo loci uiſus à ſuperficie eius, hoc eſt
              <lb/>
            ſpatium, quod diximus, abſcondit orbẽ in quarta horæ.</s>
            <s xml:id="echoid-s19704" xml:space="preserve"> Oportet ergo, ut oriatur ſol paululùm poſt
              <lb/>
            crepuſculum matutinum per quartam horæ ad minus:</s>
            <s xml:id="echoid-s19705" xml:space="preserve"> illud ergo, quod eſt inter apparitionem cre-
              <lb/>
            puſculi & apparitionẽ ſolis, eſt plus hora multò.</s>
            <s xml:id="echoid-s19706" xml:space="preserve"> Hoc autẽ, quod diximus, nõ eſt, niſi propinquitas,
              <lb/>
            propter eũ, qui non eſt exercitatus in geometricis.</s>
            <s xml:id="echoid-s19707" xml:space="preserve"> In ueritate uerò uiſus nõ peruenit ad punctum
              <lb/>
            terrę, quod iã illuminatũ eſt à ſole, niſi cũ ipſe peruenerit & cõprehẽderit cornu ipſius ſolis:</s>
            <s xml:id="echoid-s19708" xml:space="preserve"> quoniã
              <lb/>
            duæ lineæ contingẽtes unũ punctũ circuli à duabus partib.</s>
            <s xml:id="echoid-s19709" xml:space="preserve"> diuerſis cõiunctæ, ſunt linea una ſecun-
              <lb/>
            dũ rectitudinẽ [ք 14 p 1:</s>
            <s xml:id="echoid-s19710" xml:space="preserve"> quia ſemidiameter circuli ad tactus punctũ ducta, efficiet cũ utraq;</s>
            <s xml:id="echoid-s19711" xml:space="preserve"> angu-
              <lb/>
            los rectos ք 18 p 3.</s>
            <s xml:id="echoid-s19712" xml:space="preserve">] Quãdo ergo illuminatũ apparet nobis, tũ non eſt illud terra ipſa, ꝓpter id, quod
              <lb/>
            </s>
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