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-s16691" xml:space="preserve">
              <pb o="235" file="0241" n="241" rhead="OPTICAE LIBER VII."/>
            & ponat caput ſuum in punctum ultimitatis regulæ:</s>
            <s xml:id="echoid-s16692" xml:space="preserve"> & intueatur lucem, quæ eſt intra aquam:</s>
            <s xml:id="echoid-s16693" xml:space="preserve">
              <lb/>
            tunc inueniet umbram acus ſecantem lucem:</s>
            <s xml:id="echoid-s16694" xml:space="preserve"> & inueniet umbram capitis acus apud cornu regu-
              <lb/>
            læ, quod eſt apud medium lucis.</s>
            <s xml:id="echoid-s16695" xml:space="preserve"> Deinde mutet poſitionem acus, & caput eius ſit in loco eius ex
              <lb/>
            fine regulæ:</s>
            <s xml:id="echoid-s16696" xml:space="preserve"> tunc mutabitur ſitus umbræ ex luce, quæ eſt intra aquam:</s>
            <s xml:id="echoid-s16697" xml:space="preserve"> & erit umbra capitis acus
              <lb/>
            inſeparabilis à medio lucis:</s>
            <s xml:id="echoid-s16698" xml:space="preserve"> deinde auferat acum & redibit lux ad locum ſuum.</s>
            <s xml:id="echoid-s16699" xml:space="preserve"> Deinde mittat a-
              <lb/>
            cum in aquam iterum, & ponat caput eius in alio puncto finis regulę, & intueatur umbram, donec
              <lb/>
            inueniat ſecãtem lucem, quæ eſt intra aquam:</s>
            <s xml:id="echoid-s16700" xml:space="preserve"> & inueniet umbram capitis acus in medio lucis.</s>
            <s xml:id="echoid-s16701" xml:space="preserve"> De-
              <lb/>
            inde mutet poſitionem acus ſuper multitudinem punctorum ex acuitate regulæ:</s>
            <s xml:id="echoid-s16702" xml:space="preserve"> & inueniet um-
              <lb/>
            bram capitis eius ſemper in medio lucis.</s>
            <s xml:id="echoid-s16703" xml:space="preserve"> Declarabitur ergo ex hac experientia declaratione mani-
              <lb/>
            feſta, quòd lux, quæ eſt in puncto mediante lucem, quæ eſt intra aquam, quę eſt ſuper circumferen-
              <lb/>
            tiam medij circuli:</s>
            <s xml:id="echoid-s16704" xml:space="preserve"> peruenit ad illud punctum à puncto, quod eſt mediũ lucis, quæ eſt in ſuperficie
              <lb/>
            aquæ.</s>
            <s xml:id="echoid-s16705" xml:space="preserve"> Et declarabitur cum hoc, quòd hæc lux extenditur ſuper lineam rectam, quę eſt finis regulæ.</s>
            <s xml:id="echoid-s16706" xml:space="preserve">
              <lb/>
            Nam experientia eius per extremitatem acus ex diuerſis locis in fine regulę oſtendit illã tranſeun-
              <lb/>
            tem per omne punctum finis regulæ.</s>
            <s xml:id="echoid-s16707" xml:space="preserve"> Hac ergo uia experimentabitur tranſitus lucis per corpus
              <lb/>
            aquæ:</s>
            <s xml:id="echoid-s16708" xml:space="preserve"> ex quo declarabitur, quòd extenſio lucis per corpus aquæ eſt ſecundum uerticationes re-
              <lb/>
            ctarum linearum.</s>
            <s xml:id="echoid-s16709" xml:space="preserve"/>
          </p>
        </div>
        <div xml:id="echoid-div555" type="section" level="0" n="0">
          <head xml:id="echoid-head483" xml:space="preserve" style="it">4. Radi{us} medio denſiori obliqu{us}, refringitur ad perpendicularem à refractionis puncto
            <lb/>
          excitatam. 43 p 2. Idem 17 n 1.</head>
          <p>
            <s xml:id="echoid-s16710" xml:space="preserve">DEinde oportebit experimentatorem ponere ſuper centrum lucis ſignum fixum cũ ſculptio-
              <lb/>
            ne:</s>
            <s xml:id="echoid-s16711" xml:space="preserve"> deinde quan do experimentator intuebitur punctum, quod eſt in medio lucis, quę eſt in-
              <lb/>
            tra aquam:</s>
            <s xml:id="echoid-s16712" xml:space="preserve"> inueniet ipſum nõ æquidiſtans duabus extremitatibus diametri laminæ, ſed ex-
              <lb/>
            tra duas lineas perpendiculares, quę ſunt ſuper extremitatẽ diametri laminæ, quę eſt intra aquam:</s>
            <s xml:id="echoid-s16713" xml:space="preserve">
              <lb/>
            & inueniet declinationem eius ab iſta linea ad partẽ, in qua eſt ſol:</s>
            <s xml:id="echoid-s16714" xml:space="preserve"> & inueniet inter punctum, quod
              <lb/>
            eſt centrum mediæ lucis, & punctum;</s>
            <s xml:id="echoid-s16715" xml:space="preserve"> quod eſt communis differentia lineæ perpendiculari ſuper
              <lb/>
            extremitatem diametri laminæ, & puncto medio, quod eſt extremitas diametri medij circuli, tran-
              <lb/>
            ſeuntis per centrum foraminis:</s>
            <s xml:id="echoid-s16716" xml:space="preserve"> inueniet dico, diſtantiam ſenſibilem.</s>
            <s xml:id="echoid-s16717" xml:space="preserve"> Hoc declarato, oportet mitte-
              <lb/>
            re regulam ſubtilem in a quam, & applicare eam cum ſuperficie laminæ, & ponere terminum regu-
              <lb/>
            læ ſuper centrum laminę, & mouere regulam, quouſq;</s>
            <s xml:id="echoid-s16718" xml:space="preserve"> acuitas eius ſit perpendicularis ſuper ſuper-
              <lb/>
            ficiem aquæ, quò ad ſenſum:</s>
            <s xml:id="echoid-s16719" xml:space="preserve"> tune igitur inueniet centrũ lucis, quę eſt intra aquam, inter acuitatem
              <lb/>
            regulæ & lineam perpendicularem ſuper diametrum laminæ.</s>
            <s xml:id="echoid-s16720" xml:space="preserve"> Declarabitur ergo ex hoc, quòd hæc
              <lb/>
            refractio eſt ad partem perpendicularis, exẽuntis à loco refractionis perpendicularis ſuper ſuper-
              <lb/>
            ficiem aquæ.</s>
            <s xml:id="echoid-s16721" xml:space="preserve"> Cum ergo certus fuerit experimentator de hoc:</s>
            <s xml:id="echoid-s16722" xml:space="preserve"> oportebit eum ſignare apud extremi-
              <lb/>
            tatem regulæ, quę eſt ſuper circumferentiam medij circuli, quę eſt extremitas perpendicularis, ex-
              <lb/>
            euntis à centro medij circuli perpendicularis ſuper ſuperficiem aquæ, ſignum fixum, ut primum,
              <lb/>
            quod ſignatum eſt apud centrum lucis.</s>
            <s xml:id="echoid-s16723" xml:space="preserve"> Et iam declaratum eſt, quòd lux, quę peruenit ad punctum,
              <lb/>
            quod eſt centrum lucis, quæ eſt intra aquam, eſt lux extenſa ſecundum rectitudinem lineæ conti-
              <lb/>
            nuantis duo centra foraminum:</s>
            <s xml:id="echoid-s16724" xml:space="preserve"> & hæc linea peruenit ad cẽtrum medij circuli æquidiſtantis ſuper-
              <lb/>
            ficiei laminæ:</s>
            <s xml:id="echoid-s16725" xml:space="preserve"> & eſt illius diameter.</s>
            <s xml:id="echoid-s16726" xml:space="preserve"> Si hęc linea fuerit extenſa in imaginatione ſecundum rectitudi-
              <lb/>
            nem intra aquam, donec perueniat ad oram laminæ:</s>
            <s xml:id="echoid-s16727" xml:space="preserve"> tunc igitur erit æquidiſtans diametro laminæ,
              <lb/>
            & perueniet ad lineam perpendicularem in interiore parte oræ laminæ.</s>
            <s xml:id="echoid-s16728" xml:space="preserve"> Et cum centrum lucis, quę
              <lb/>
            eſt intra aquam, non eſt ſuper perpendicularem lineam oræ laminæ:</s>
            <s xml:id="echoid-s16729" xml:space="preserve"> tunc lux, quę extenditur à me-
              <lb/>
            dio lucis, quę eſt in ſuperficie aquæ, ad medium lucis, quæ eſt intra aquam, non extenditur ſecun-
              <lb/>
            dum rectitudinem lineæ tranſeuntis per centra duorum foraminum, ſed refringitur.</s>
            <s xml:id="echoid-s16730" xml:space="preserve"> Declaratum
              <lb/>
            eſt autem, quòd hæc lux extẽditur rectè à medio lucis, quę eſt in ſuperficie aquæ, ad medium lucis,
              <lb/>
            quæ eſt intra aquam.</s>
            <s xml:id="echoid-s16731" xml:space="preserve"> Ergo refractio huius lucis eſt apud ſuperficiem aquæ.</s>
            <s xml:id="echoid-s16732" xml:space="preserve"/>
          </p>
        </div>
        <div xml:id="echoid-div556" type="section" level="0" n="0">
          <head xml:id="echoid-head484" xml:space="preserve" style="it">5. Radij incidentiæ & refractionis ſunt in uno plano. 46 p 2.</head>
          <p>
            <s xml:id="echoid-s16733" xml:space="preserve">ET iam declaratum eſt, quòd hæc lux tranſit per centra duorum foraminum, & per medium
              <lb/>
            lucis, quæ eſt in ſuperficie aquæ, quod eſt centrum circuli medij, æquidiſtantis ſuperficiei la-
              <lb/>
            minæ, & per medium lucis, quæ eſt intrà aquam, quod eſt in circumferentia medij circuli.</s>
            <s xml:id="echoid-s16734" xml:space="preserve"> Ex
              <lb/>
            quo patet, quòd lumen perueniens ad centrum lucis, quæ eſt intra aquam, dum extenditur in aere,
              <lb/>
            & poſtquam refringitur intra aquã, eſt in eadem ſuperficie æquali, ſcilicet in ſuperficie circuli me-
              <lb/>
            dij trium circulorũ, qui ſunt in interiore parte oræ inſtrumenti.</s>
            <s xml:id="echoid-s16735" xml:space="preserve"> Et refractio hæc inuenitur, quando
              <lb/>
            linea tranſiens per centra foraminum fuerit decliuis ſuper ſuperficiem aquæ, non perpendicularis.</s>
            <s xml:id="echoid-s16736" xml:space="preserve">
              <lb/>
            Et nunquam erit hæc linea perpẽdicularis ſuper ſuperficiem aquæ in hora tranſitus lucis ſolis, niſi
              <lb/>
            quando fuerit ſol in uertice capitis:</s>
            <s xml:id="echoid-s16737" xml:space="preserve"> & hoc erit in aliquibus locis, & non in omnibus:</s>
            <s xml:id="echoid-s16738" xml:space="preserve"> & in quibuſ-
              <lb/>
            dam temporibus, non in omnibus:</s>
            <s xml:id="echoid-s16739" xml:space="preserve"> neq;</s>
            <s xml:id="echoid-s16740" xml:space="preserve"> tranſit ſol per uerticem capitis habitantium in pluribus lo-
              <lb/>
            cis habitationis:</s>
            <s xml:id="echoid-s16741" xml:space="preserve"> & in quibus tranſit:</s>
            <s xml:id="echoid-s16742" xml:space="preserve"> in iſtis locis diſtinguetur hęc experimentatio in omni tempo-
              <lb/>
            re:</s>
            <s xml:id="echoid-s16743" xml:space="preserve"> illi autem ſuper quorum zenit h tranſit ſol, ſi uoluerint hoc experiri, cauebũt tempus, in quo ſol
              <lb/>
            tranſit per capita eorum.</s>
            <s xml:id="echoid-s16744" xml:space="preserve"/>
          </p>
        </div>
        <div xml:id="echoid-div557" type="section" level="0" n="0">
          <head xml:id="echoid-head485" xml:space="preserve" style="it">6. Radi{us} medio rariori perpendιcularis, irrefract{us} penetrat. 44 p 2.</head>
          <p>
            <s xml:id="echoid-s16745" xml:space="preserve">ITẽ accipiat exքimẽtator fruſta uitri clari, quorũ figuræ ſint cubicæ:</s>
            <s xml:id="echoid-s16746" xml:space="preserve"> & ſit lõgitudo uniuſcuiuſq;</s>
            <s xml:id="echoid-s16747" xml:space="preserve">
              <lb/>
            </s>
          </p>
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