Vitruvius Pollio, I dieci libri dell?architettura, 1567

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    <archimedes>
      <text>
        <body>
          <chap>
            <subchap1>
              <subchap2>
                <p type="main">
                  <s id="s.006870">
                    <pb pagenum="375" xlink:href="045/01/389.jpg"/>
                    <emph type="italics"/>
                  che è da un centro all'altro. </s>
                  <s id="s.006871">ſi chiamano lunghezze medie riſpetto, che quel punto, che è rimo­
                    <lb/>
                  tißimo dal centro del mondo, che ſi chiama giogo, è detto anche lunghezza piu lontana, & quel
                    <lb/>
                  lo, che è uicinißimo al detto centro, che chiamano opposto al giogo, è detto lunghezza piu ui­
                    <lb/>
                  cina dello Eccentrico, ouero dello Epiciclo. </s>
                  <s id="s.006872">Queſti due punti ſono termini d'una linea dritta,
                    <lb/>
                  che paſſa per amendue i centri, laquale ſi chiama linea del giogo: percioche è dimostratrice del
                    <lb/>
                  giogo. </s>
                  <s id="s.006873">la onde ſi come nello Eccentrico la maggior lontananza è tanto piu del ſemidiametro del
                    <lb/>
                  lo Eccentrico, quanto è lo ſpacio, che è tra uno centro & l'altro: coſi la minore è tanto meno del
                    <lb/>
                  ſemidiametro, quanto quella è di piu: & il ſemidiametro è la lunghezza media. </s>
                  <s id="s.006874">Similmente nello
                    <lb/>
                  Epiciclo la lunghezza maggiore ſarà tanto piu d'uno ſpacio, che è tra uno centro, & l'altro, quan
                    <lb/>
                  to è il ſemidiametro dello Epiciclo: & tanto dallo iſteſſo ſpacio ſarà ſuperata la minore. </s>
                  <s id="s.006875">la onde
                    <lb/>
                  lo ſpacio che ſarà tra l'uno centro, & l'altro ſarà la diſtanza di mezo, che media lunghezza ſi
                    <lb/>
                  chiama. </s>
                  <s id="s.006876">percioche è molto ragioneuole, che la lunghezza media ſia tanto meno della maggiore,
                    <lb/>
                  quanto eſſa è di piu della minore. </s>
                  <s id="s.006877">Chi bene conſidera quello, che fin hora s'è detto, comprenderà,
                    <lb/>
                  che tanto nello Eccentrico, quanto nello Epiciclo qualunque punto, quanto ſi trouerà nella cir­
                    <lb/>
                  conferenza piu rimoto & diſcosto dalla lunghezza maggiore, tanto ſarà piu uicino al centro del
                    <lb/>
                  mondo: & quelli punti, che ſaranno egualmente diſtanti dal punto del giogo, ſaranno anche egual
                    <lb/>
                  mente diſtanti dal centro del mondo. </s>
                  <s id="s.006878">Da queste coſe ſi ha tutta la diuerſità del mouimento, che
                    <lb/>
                  ci appare, cioè con queſte deſcrittioni ſi ſalua la diuerſità di tutte le apparenze, & però molto
                    <lb/>
                  cautamente ſi deono intendere questi uocaboli, perche ſono ſtati ritrouati per dare ad intendere
                    <lb/>
                  le coſe del cielo a quel modo, che ſi puo: perche non ſi troua, nè Epiciclo, ne Giogo, nè Deferen­
                    <lb/>
                  te, nè altra coſa ſimigliante nel mondo. </s>
                  <s id="s.006879">Vediamo adunque come ſi troua la diuerſità de i mo­
                    <lb/>
                  uimenti. </s>
                  <s id="s.006880">Ma prima poniamo la figura delle coſe dette.
                    <emph.end type="italics"/>
                  </s>
                </p>
                <p type="main">
                  <s id="s.006881">
                    <emph type="italics"/>
                  a b. è il deferente.
                    <emph.end type="italics"/>
                  </s>
                </p>
                <p type="main">
                  <s id="s.006882">
                    <emph type="italics"/>
                  c. il centro del deferente.
                    <emph.end type="italics"/>
                  </s>
                </p>
                <p type="main">
                  <s id="s.006883">
                    <emph type="italics"/>
                  d e. lo epiciclo.
                    <emph.end type="italics"/>
                  </s>
                </p>
                <p type="main">
                  <s id="s.006884">
                    <emph type="italics"/>
                  a. il centro dello epiciclo.
                    <emph.end type="italics"/>
                  </s>
                </p>
                <p type="main">
                  <s id="s.006885">
                    <emph type="italics"/>
                  f. il centro del mondo.
                    <emph.end type="italics"/>
                  </s>
                </p>
                <p type="main">
                  <s id="s.006886">
                    <emph type="italics"/>
                  a. il giogo del deferente.
                    <emph.end type="italics"/>
                  </s>
                </p>
                <p type="main">
                  <s id="s.006887">
                    <emph type="italics"/>
                  b. l'oppoſto al giogo.
                    <emph.end type="italics"/>
                  </s>
                </p>
                <p type="main">
                  <s id="s.006888">
                    <emph type="italics"/>
                  d. il giogo dell'epiciclo.
                    <emph.end type="italics"/>
                  </s>
                </p>
                <figure id="id.045.01.389.1.jpg" xlink:href="045/01/389/1.jpg" number="113"/>
                <p type="main">
                  <s id="s.006889">
                    <emph type="italics"/>
                  Poniamo caſo, che'l pianeta ſi moua portato immediate dal
                    <lb/>
                  ſuo Epiciclo, benche egli ſi moua egualmente ſopra il ſuo cen­
                    <lb/>
                  tro, non dimeno pare, che egli muti il ſuo tenore ſopra qualun­
                    <lb/>
                  que altro punto, che ſia nel cerchio, & ſimilmente ſopra il cen
                    <lb/>
                  tro del mondo. </s>
                  <s id="s.006890">Queſta mutatione ſi ſalua per ragione di proſpettiua, imperoche posto, che mol­
                    <lb/>
                  te coſe ſi mouino con eguale uelocità, pure quelle che ſono piu lontane da noi pareno men ueloci,
                    <lb/>
                  che le piu uiciue. </s>
                  <s id="s.006891">Et però hauendo compreſo gli Aſtronomi, che il Sole in diuerſi luoghi del Zo­
                    <lb/>
                  diaco, diuerſamente ſi muoue, & uolendo ſaluare tanta diuerſità, & non uolendo attribuire ad
                    <lb/>
                  un corpo ſi nobile tanta diſagguaglianza, ſi hanno imaginato diuerſi cerchi, i centri de i quali
                    <lb/>
                  non fuſſero gli iſteſſi, col centro del Mondo. </s>
                  <s id="s.006892">Egli adunque adiuiene, che piu lenta ci appare una
                    <lb/>
                  ſtella, eſſendo nel giogo, che lontana dal giogo, perche nel giogo è piu rimota. </s>
                  <s id="s.006893">Ecci un'altro
                    <lb/>
                  modo di diuerſità nel mouimento, perche ſe il pianeta dallo epiciclo, & lo epiciclo dal concentri
                    <lb/>
                  co portato fuſſe, non però ſarebbe meno la diuerſità, imperoche il pianeta portato dall'uno, &
                    <lb/>
                  l' altro uerſo leuante, ſenza dubbio andrebbe piu ueloce, che ſe fuſſe portato dal concentrico ſo­
                    <lb/>
                  lo, & per lo epiciclo ſe ne steſſe, o ſe ne tornaſſe a dietro, percioche nel toccamento di quelle li­
                    <lb/>
                  nee, che ſi parteno dal centro, & uanno all'epiciclo, pare che la ſtella, quanto al mouimento del
                    <lb/>
                  lo epiciclo, ſi ſtia, ma in una metà della circonferenza pare, che uada inanzi, & nell'altra,
                    <emph.end type="italics"/>
                  </s>
                </p>
              </subchap2>
            </subchap1>
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