Caverni, Raffaello, Storia del metodo sperimentale in Italia, 1891-1900

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              Tractatus Marci Antonii De Dominis, per Joannem Bartolum in lucem
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              editus.
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              <s>L'Autore mostra di avere avuto e di aver tuttavia una gran fiducia di
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              esser coll'opera sua riuscito a sodisfar pienamente e con gran facilità al de­
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              siderio di coloro, che volevan saper la maniera e la ragione del ritrovato
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              olandese. </s>
              <s>Una tal fiducia vien da lui stesso espressa per le seguenti parole:
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              “ Ex hactenus a nobis dictis et explicatis de vitreis perspicillis, facillimum
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              negotium redditur in conficiendo instrumento illo quod nuper videtur in­
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              ventum aut saltem, praesertim in Italia, publicatum. </s>
              <s>Id enim, quemadmo­
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              dum maxima admiratione affecit et afficit plurimos, ita mihi certe qui in
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              perspectivis ante multos, sed per multos etiam annos delectationis causa men­
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              tem exercui, nulli prorsus fuit admirationi, sed cum primum illud vidi, erat
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              autem valde imperfectum, effectum duorum vitrorum aperte cognovi ” (ivi,
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              pag. </s>
              <s>37, 38). </s>
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              <s>Questa vantata facilità d'intendere ciò che a tutti era sembrato tanto
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              difficile, il
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              De Dominis
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              la riconosce dunque dall'essersi per tanti anni eser­
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              citato negli studi di Prospettiva, e dall'aver saputo spiegare le proprietà delle
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              lenti. </s>
              <s>E infatti egli aveva sufficientemente bene dimostrato l'ingrandimento
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              virtuale delle immagini nelle lenti convesse, concludendo così la sua dimo­
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              strazione: “ Itaque oculus non videt quantitatem sub angulo directo et na­
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              turali, sed sub angulo, qui est angulus maior ” (pag. </s>
              <s>19). Aveva pure in
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              sufficiente maniera descritto il rappresentarsi delle immagini virtuali nelle
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              lenti concave, concludendo così intorno ad esse: “ Oculus videt quantitatem
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              sub angulo qui est minor et strictior angulo naturali, et minorem vitri par­
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              tem occupat et consequenter res quidem minor apparebit, sed clarior et
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              distinctior ” (ibi). </s>
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              <s>Tali diottriche conclusioni però, benchè vere e sufficientemente dimo­
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              strate, non eran quelle che più facevano all'uopo. </s>
              <s>Imperocchè, consistendo
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              la ragione del Canocchiale nell'immagine reale e rovesciata dell'obiettivo,
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              che viene ingrandita e raddirizzata dall'oculare, il De Dominis intorno a ciò
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              mostra di non saperne niente, e perciò, riguardandosi da lui l'obiettivo stesso
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              come una lente d'ingrandimento virtuale, ecco come frantende l'ufficio del­
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              l'oculare, e come allo stesso tempo lasci gli studiosi in quella fame, a cui
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              con tanta facilità aveva fiducia di sodisfare. </s>
              <s>“ Caeterum iam vidimus quae
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              valde remota sunt, per vitrum lenticulare cerni quidem cum ipsorum in­
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              cremento, remoto usque ad certum spacium ab oculo vitro praedicto, sed
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              turbate et indistincte, et confuse, propter mixtionem radiorum visualium di­
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              rectorum cum fractis. </s>
              <s>Si igitur aliqua ratione tolli posset haec confusio, ita
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              ut sublatis radiis directis per solos refractos fiat visio, ex duplici capite illa
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              clara esset et distincta, tum ex sublata confusione praedicta, tum ex rerum
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              visibilium dilatatione. </s>
              <s>Tollitur igitur confusio illa et extinguntur radii di­
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              recti, per appositionem vitri excavati inter oculum et vitrum lenticulare ”
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              (ibi, pag. </s>
              <s>34). </s>
            </p>
            <p type="main">
              <s>Tale e tanto in
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              era il fervor de'nuovi studi dioffrici in Ita-</s>
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