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

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      <text>
        <body>
          <chap>
            <pb xlink:href="020/01/1944.jpg" pagenum="187"/>
            <p type="main">
              <s>“ La percossa del grave, egli dice, che discendendo percote l'addiman­
                <lb/>
              deremo
                <emph type="italics"/>
              percossa naturale. </s>
              <s>Percossa violenta
                <emph.end type="italics"/>
              intenderemo quella del grave,
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              che ascendendo percote.
                <emph type="italics"/>
              Percossa media
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              diremo quella del grave, che mo­
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              vendosi orizzontalmente percote.
                <emph type="italics"/>
              Percossa composta
                <emph.end type="italics"/>
              diremo quella di quel
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              grave, il cui moto naturale è accelerato da motore estrinseco, e con tal moto
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              accelerato percota. </s>
              <s>” </s>
            </p>
            <p type="main">
              <s>“ La percossa opera con la velocità e con la copia della materia, in
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              cui s'imprime detta velocità, e però se caderanno dalla medesima altezza
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              due gravi disuguali dell'istessa materia, come due palle di ferro disuguali,
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              le loro percosse saranno disuguali, e maggiore sarà la percossa della mag­
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              gior palla, benchè ambedue discendano con la medesima velocità ” (MSS.
                <lb/>
              Gal. </s>
              <s>Disc., T. XVIII, fol. </s>
              <s>95). </s>
            </p>
            <p type="main">
              <s>Ora questo, che sembrava essere approvato dall'esperienza, si voleva
                <lb/>
              dall'Aggiunti confermare con la teoria, dimostrando che i momenti, o più
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              in generale le quantità di moto, son matematicamente proporzionali al pro­
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              dotto delle velocità per le quantità della materia. </s>
              <s>La proposizione era quella
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              stessa XXVII dimostrata quarant'anni dopo nel trattato
                <emph type="italics"/>
              De vi percussionis,
                <emph.end type="italics"/>
                <lb/>
              e come ivi il Borelli la conclude dalle due proposizioni precedenti, così
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              avrebbe voluto fare l'Aggiunti, proponendosi di dimostrar come, essendo le
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              moli eguali, i momenti stanno in ragione delle velocità, ed essendo le ve­
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              locità uguali stanno essi momenti in diretta ragion delle moli. </s>
            </p>
            <p type="main">
              <s>La prima di queste proposizioni non si trova a suo luogo, e invece se
                <lb/>
              ne legge nel manoscritto un'altra, che potrebbesi dire un corollario di
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              lei, se non fosse una falsità manifesta o una di quelle arguzie delle quali
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              si trova nelle speculazioni dell'Aggiunti più di un esempio. </s>
              <s>La detta pro­
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              posizione, che tiene nel citato manoscritto il luogo della prima, è così for­
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              mulata: “ Anco la sola velocità senza il peso opera ed ha momento ” (ivi
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              a tergo). Aveva Aristotile sentenziato “ che senza l'inerenza del suo sog­
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              getto non può nè essere nè anco immaginarsi alcun movimento ” sentenza
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              che, ripetuta da Simplio nel II dialogo Dei due massimi sistemi, è dal Sa­
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              gredo ivi approvata per vera. </s>
              <s>Volle nonostante l'Aggiunti, così argutamente
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              discorrendo, contradire al giudizio di Aristotile e di Galileo, ciò che avrebbe
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              avuto il diritto di fare, quando non avesse contradetto insieme alla ragion
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              matematica, perchè se una delle quantità componenti il momento è zero, dee
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              necessariamente il momento stessa ridursi a zero: </s>
            </p>
            <p type="main">
              <s>“ Che la velocità, senza il peso, operi ed abbia forza, è manifesto nei
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              venti, i quali, non essendo altro che aria mossa nell'aria (perchè un grave
                <lb/>
              in un mezzo ugualmente grave in specie ad esso, come dimostra Archimede,
                <lb/>
              non ha peso alcuno in detto mezzo) adunque tutta la forza del vento na­
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              sce dalla sola velocità, con la quale si muove l'aria. </s>
              <s>È ancora manifesto
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              nelle percosse violente perchè, facendosi la percossa violenta dal grave al­
                <lb/>
              l'insù, ed essendo l'inclinazione del grave all'ingiù, l'effetto dunque della
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              percossa non può nascere dal peso, cioè dalla propensione all'ingiù, ma sì
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              bene dalla velocità impressagli all'insù. </s>
              <s>È finalmente questo stesso manife-</s>
            </p>
          </chap>
        </body>
      </text>
    </archimedes>
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