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

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              <s>
                <pb xlink:href="020/01/543.jpg" pagenum="524"/>
              gnava, secondo riferisce il Porta, a conoscer se il mosto era puro, o s'era
                <lb/>
              stato mescolato coll'acqua. </s>
              <s>“ Unde si in mustum mala vel pyra silvestria
                <lb/>
              immiseris, et mustum purissimum erit, supernatabunt mala et fluitabunt. </s>
              <s>At
                <lb/>
              si aquam admistam habuerint, mala fundum petunt introque merguntur. </s>
              <s>
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              Cum enim aqua musto tenuior sit, et levior facit ut malum subsidat. </s>
              <s>Quod
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              optime a Sotione descriptum est et satis curiose. </s>
              <s>Inquit: ut sciamus mustum
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              an aquam habeat, pyra silvestria, hoc est crudissima, in mustum coniice, et
                <lb/>
              si quidem aquam habuerit ad fundum mergentur. </s>
              <s>Nam si vas musto repleas,
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              dum sorbum aut pyrum immerges, supernatabit, quanto plus aquae addes,
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              plus mergetur malum ” (Magia Nat, Lugd. </s>
              <s>Batav. </s>
              <s>1651, pag. </s>
              <s>618, 19). </s>
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              <s>Galileo, il quale non immeritamente si riconosce per primo inventore
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              dell'Areometro, applicato agli usi della scienza, nella I Giornata delle Due
                <lb/>
              Nuove Scienze, descrive il seguente dialogo passato fra il Sagredo e il Sal­
                <lb/>
              viati: “ — Io con un altro artifizio ingannai alcuni amici, appresso i quali
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              m'era vantato di ridurre quella palla di cera al giusto equilibrio con l'acqua,
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              ed avendo messo nel fondo del vaso una parte d'acqua salata e sopra quella
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              della dolce, mostrai loro la palla, che a mezz'acqua si fermava, e spinta nel
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              fondo o sospinta ad alto nè in questo nè in quel sito restava, ma ritornava
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              nel mezzo. </s>
              <s>— Non è cotesta esperienza priva d'utilità, perchè, trattandosi
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              dai medici in particolare, delle diverse qualità di acqua e tra l'altre prin­
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              cipalmente della leggerezza e gravità più di questa che di quella, con una
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              simil palla aggiustata, sicchè resti ambigua per così dire tra lo scendere e
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              il salire in un'acqua, per minima che sia la differenza di peso tra due acque,
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              se in una tal palla scenderà, nell'altra che sia più grave salirà ” (Alb. </s>
              <s>XIII, 72). </s>
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              <s>Dalle citate parole sembra che, rispetto alla invenzione, sieno da distin­
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              guere due tempi: il primo, in cui la palla galleggiante non serviva ad altro
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              che alla curiosità di uno spettacolo, e il secondo in cui si fece di questa
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              stessa palla galleggiante l'applicazione all'uso areometrico. </s>
              <s>Il primo tempo
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                <figure id="id.020.01.543.1.jpg" xlink:href="020/01/543/1.jpg" number="65"/>
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              <s>Figura 57.
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              par doversi ridurre intorno al 1604, come si rileva da una lettera
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              di Don Antonio de'Medici che fa richiesta a Galieo della palla spet­
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              tacolosa. </s>
              <s>“ Intendo (diceva quella lettera che è del 28 Giugno) che
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              V. S. ha una palla, che gettandola nell'acqua sta fra le due acque. </s>
              <s>
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              Vengo con la presente a pregarla vivamente di voler favorirmene
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              e consegnarla al P. D. </s>
              <s>Antonio Cerrato ” (Volinski, Lett. </s>
              <s>in. </s>
              <s>a
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              Gal., Firenze 1874, Lett. </s>
              <s>IV, pag. </s>
              <s>16). </s>
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              <s>Quanto al secondo tempo, potrebb'essere che fosse verso il 1612,
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              quando pensò di trovare il peso specifico dell'aria, riducendo il
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              galleggiante in figura di quella caraffalla, che fu poi, in quasi
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              tutte le varie forme di questo strumento, adottata dai successivi
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              inventori. </s>
              <s>Così infatti ce ne descrive Galileo la figura e l'uso in
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              una Lettera al Nozzolini: “ Facciasi un vaso di vetro simile al­
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              l'ABC (fig. </s>
              <s>57) di qualsivoglia grandezza col collo AB lunghetto al­
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              quanto ma stretto, e nel fondo C se gli attacchi tanto piombo o altro peso
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                <gap/>
              si sommerga, sicchè solo avanzi fuori del-</s>
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