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

Table of figures

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            <p type="main">
              <s>
                <pb xlink:href="020/01/289.jpg" pagenum="270"/>
              progressi, che non può tacer di loro la nostra Storia. </s>
              <s>Ma prima, convien tratte­
                <lb/>
              nerci alquanto sulle applicazioni di quella esperienza eroniana, che per es­
                <lb/>
              sere stata genitrice dello strumento da misurare il calore, e per essere stata
                <lb/>
              soggetto di novità spettacolose, si è acquistata perciò, per noi, una parti­
                <lb/>
              colare importanza. </s>
            </p>
            <p type="main">
              <s>
                <emph type="center"/>
              II.
                <emph.end type="center"/>
              </s>
            </p>
            <p type="main">
              <s>Nel libro degli
                <emph type="italics"/>
              Spiritali
                <emph.end type="italics"/>
              tradotto, come i nostri lettori sanno, nel 1606,
                <lb/>
              ma scritto originalmente in latino nel 1601, il Porta descriveva così l'espe­
                <lb/>
              rienza eroniana, con intenzione d'applicarla ad uso diverso sì, ma non punto
                <lb/>
              meno importante di quello, a cui seppe ingegnosamente applicarla il Santorio: </s>
            </p>
            <p type="main">
              <s>“ Sia il vaso A (fig. </s>
              <s>4); questo abbi la bocca dentro
                <lb/>
                <figure id="id.020.01.289.1.jpg" xlink:href="020/01/289/1.jpg" number="11"/>
              </s>
            </p>
            <p type="caption">
              <s>Figura 4.
                <lb/>
              un vaso B, piano, pieno d'acqua, il quale vaso sarà pieno
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              di aria, grosso nella sua consistenza, più o meno, secondo
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              il luogo e la stagione. </s>
              <s>Poi accosterete un vaso pieno di
                <lb/>
              fuoco al corpo del vaso in A, e l'aria, subito riscaldan­
                <lb/>
              dosi, si anderà assottigliando, e fatta più sottile, vuole più
                <lb/>
              gran luogo, e cercando uscir fuori, verrà fuori dell'acqua,
                <lb/>
              e si vedrà l'acqua bollire, che è segno che l'aria fugge,
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              e quanto si andrà più riscaldando, l'acqua più boglierà,
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              ma, essendo ridotta tenuissima, l'acqua non boglierà più. </s>
              <s>
                <lb/>
              All'hora rimovete il vaso del fuoco dal ventre A, e l'aria
                <lb/>
              rinfrescandosi, s'andrà ingrossando, e vuol minor luogo, e
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              non havendo come riempir il vano del vaso, perchè ha la
                <lb/>
              bocca sotto l'acqua, tirerà a sè l'acqua del vaso, e si vedrà
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              salir l'acqua su con gran furia a riempir tutto il vaso, lasciando vacua quella
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              parte, dove l'aria stà ridotta già nella sua natura di prima. </s>
              <s>E se di nuovo
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              accostarete il fuoco a quella poca aria, attenuandosi di nuovo, calerà giù
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              tutta l'acqua, e rimovendo il fuoco tornerà a salir l'acqua ” (Napoli 1606,
                <lb/>
              pag. </s>
              <s>77). L'esperienza stessa però, come semplice curiosità spettacolosa, era
                <lb/>
              stata descritta già dall'Autore nel cap. </s>
              <s>XXII del secondo fra i Quattro libri
                <lb/>
              della Magia, e nel cap. </s>
              <s>I dell'ottavo della Magia stessa in XX libri. </s>
            </p>
            <p type="main">
              <s>La gran diffusione, che ebbero queste varie opere del Porta, rese l'espe­
                <lb/>
              rienza eroniana quasi diremmo popolare, e alcuni destramente pensarono di
                <lb/>
              servirsene a dimostrarla al pubblico, qual'effetto spettacoloso, e per metterla
                <lb/>
              a prezzo, con Re e con principi, come un segreto de'più preziosamente ge­
                <lb/>
              losi. </s>
              <s>Giuliano de'Medici scriveva così da Praga a Galileo, nell'Ottobre del
                <lb/>
              1610: “ Non voglio restar di dirle che qui ci è un Fiammingo, che viene
                <lb/>
              d'Inghilterra, che pretende avere trovato il moto perpetuo, ed avendone
                <lb/>
              solo prima dato uno strumento al Re d'Inghilterra, ne ha dato un altro a </s>
            </p>
          </chap>
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