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

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            <p type="main">
              <s>
                <pb xlink:href="020/01/360.jpg" pagenum="341"/>
              niere au-devante le prunelle. </s>
              <s>Il est bien vrai que le prunelle nous décou­
                <lb/>
              vré tout l'hemisphère à la fois: l'artefice que j indique ne decouvrirà qu'un
                <lb/>
              astre. </s>
              <s>Mais cet astre serà grand: la Lune aussi deviendrà plus grande, et
                <lb/>
                <figure id="id.020.01.360.1.jpg" xlink:href="020/01/360/1.jpg" number="33"/>
              </s>
            </p>
            <p type="caption">
              <s>Figura 25.
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              nous connoîtrons mieux la figure de sas
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              taches ” (Essai, etc., Paris 1797, pag. </s>
              <s>23). </s>
            </p>
            <p type="main">
              <s>Il Venturi vorrebbe far credere che qui
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              Leonardo avesse descritto un canocchiale,
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              ma pure è chiaro che il modo d'avvalorar
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              la vista in tale vinciana invenzione è fondato
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              sopra un effetto ottico molto differente da
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              quelli soliti d'operarsi o dalle lenti cristalline o dagli specchi. </s>
              <s>L'effetto ottico
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              ivi speculato, e l'applicazione di lui a veder, secondo Leonardo, gli oggetti più
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              di lontano, son cose meritevolissime della nostra attenzione, riconoscendo­
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              visi l'Autore studioso di adattare un tubo a portar lontano la luce, o, se­
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              condo lui, le specie visibili, a quel modo che si adatta così efficacemente a
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              portar più lontano i suoni. </s>
              <s>Mirabile è questo inaspettato riscontro intrave­
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              duto tra il
                <emph type="italics"/>
              Portaluce
                <emph.end type="italics"/>
              e il
                <emph type="italics"/>
              Portavoce,
                <emph.end type="italics"/>
              ma è ben più mirabile che a quello
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              stesso riscontro vi fosse condotto Leonardo, non a caso, ma per via di re­
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              condita scienza della natura della luce e de'suoni, e delle proprietà de'raggi
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              sonori; scienza ignorata in gran parte, come si dimostrerà nel progresso
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              della nostra Storia, dagli stessi Fisici del secolo XVII. </s>
              <s>Per Leonardo tanto
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              la luce che i suoni si diffondono in sfere o in raggi divergenti, ed è que­
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              sta la ragione per cui va languendo, per via delle distanze, la vivacità
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              delle immagini e la intensità delle voci. </s>
              <s>Dentro i tubi i raggi lucidi e i so­
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              nori, impediti di divergere, si mantengono paralleli e portan perciò più lon­
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              tano le specie visibili e i tremori armonici. </s>
              <s>Si comprende bene che la spe­
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              culazione del nuovo strumento ottico proposto nel Manoscritto vinciano è
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              fondato sopra la falsa ipotesi platonica de'raggi luminosi che si muovon dal­
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              l'occhio di chi guarda, come i raggi sonori si muovon dalle labbra di chi
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              parla, ma se è vero che la luce si propaghi in onde come il suono, non vi
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              è dubbio che, per lo strumento e per la teoria di Leonardo, i tubi chiusi
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              debbono operar sulla vista qualche altro più sottile e più recondito effetto,
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              oltre i consueti assegnati dagli Ottici, che son quelli di riparar l'occhio dalla
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              soverchia luce diffusa, e dalle riflessioni irregolari. </s>
            </p>
            <p type="main">
              <s>In ogni modo riman pur ancora lontana dal vero la sentenza del Ven­
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              turi, che nel
                <emph type="italics"/>
              Portaluce
                <emph.end type="italics"/>
              di Leonardo da Vinci vorrebbe veder descritto uno
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              de'canocchiali moderni, essendo tutti gli scrittori concordi in affermare che
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              l'invenzione di così utile strumento non occorse prima che al cominciar del
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              secolo XVII Cercar chi ne fosse primo Autore e come vi riuscisse, è im­
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              presa vana, perchè segue delle invenzioni quel che segue dell'erbe, le quali
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              avendo i germi piccoli e sotto terra, non se ne conoscon le virtù nè se ne
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              sanno i nomi, se non dappoichè sono uscite fuori e hanno aperte le foglie
                <lb/>
              all'aria. </s>
              <s>Pure, non son mancati alcuni, i quali hanno preteso di saper la
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              prima origine e il nome dell'inventore del Canocchiale e ne hanno compo-</s>
            </p>
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