Vitruvius Pollio, I dieci libri dell?architettura, 1567

Table of figures

< >
< >
page |< < of 520 > >|
    <archimedes>
      <text>
        <body>
          <chap>
            <subchap1>
              <subchap2>
                <p type="main">
                  <s id="s.007458">
                    <pb pagenum="402" xlink:href="045/01/416.jpg"/>
                    <emph type="italics"/>
                  un circolo, hora la parabole, hora la hiperbole, hora la ellipſe. </s>
                  <s id="s.007459">il che come ſia dirò breuemen­
                    <lb/>
                  te. </s>
                  <s id="s.007460">Il Sole ouero ſi truoua nello equinottiale, ouero fuori dello equinottionale. </s>
                  <s id="s.007461">Se egli ſi truoua
                    <lb/>
                  nello equinottiale, egli caminando d'intorno a quel circolo, & gettando i raggi ſuoi nel Gnomo­
                    <lb/>
                  ne, farà in ogni piano di horologio, che la cima del Gnomone con l'ombra deſcriuerà una linea
                    <lb/>
                  dritta in quel giorno, che egli è nello equinottiale: & però in tutti gli horologi de piani eguali, lo
                    <lb/>
                  equinottiale è ſegnato con una linea dritta. </s>
                  <s id="s.007462">& la ragione è, perche la cima del Gnomone è nel pia
                    <lb/>
                  no dello equinottiale, & però l'ombre mandate dal Gnomone, non ſi partiranno da quello nel tem
                    <lb/>
                  po dello equinottio. </s>
                  <s id="s.007463">Et però ſaranno terminate dal taglio commune di quel piano dell'horologio,
                    <lb/>
                  & dello equinottiale, come praticando ſi conoſcerà chiaramente. </s>
                  <s id="s.007464">Girando adunque il Sole nello
                    <lb/>
                  equinottiale, & mandando i raggi ſuoi alla cima del Gnomone, l'ombra, che uiene dalla detta
                    <lb/>
                  cima deſcriuerà in ogni piano eguale una linea dritta, la quale ſarà egualmente diſtante al taglio
                    <lb/>
                  commune dello equinottiale, & di quel piano doue ſi ſtende l'ombra, che è il piano dell'horolo­
                    <lb/>
                  gio. </s>
                  <s id="s.007465">Ma perche il Sole per lo mouimento del primo cielo fa ogni giorno un circolo egualmente di
                    <lb/>
                  ſtante dallo equinottiale, & per lo obliquo ſuo mouimento s'allentana dallo equinottiale: però
                    <lb/>
                  non eſſendo egli nell'equinoltiale puo auuenire, che il piano, ſopra il quale è mandata l'ombra dal­
                    <lb/>
                  la cima del Gnomone ſi tagli con quel circolo, per lo quale il Sole ſi gira. </s>
                  <s id="s.007466">& puo anche eſſere,
                    <lb/>
                  che non ſi tagli. </s>
                  <s id="s.007467">Imaginiamo, che il Sole ogni giorno ſalendo, & girando laſci nel cielo i ueſti­
                    <lb/>
                  gij del ſuo camino come di fuoco, & deſcriua un circolo. </s>
                  <s id="s.007468">queſto circolo ouero ſarà tutto ſopra
                    <lb/>
                  terra, ouero parte ſotto, & parte di ſopra. </s>
                  <s id="s.007469">Se ſarà parte di ſotto, & parte di ſopra, il che non
                    <lb/>
                  è altro, che tagliare il piano dell'horologio, allhora la eſtremità dell'ombra del Gnomone deſcri­
                    <lb/>
                  uerà nel piano la hiperbole. </s>
                  <s id="s.007470">ma ſe quel circolo ſarà tutto di ſopra, ouero toccherà il piano, oue­
                    <lb/>
                  ro non lo toccherà. </s>
                  <s id="s.007471">Se lo toccherà l'ombra del Gnomone, deſcriuerà nel piano la linea detta pa
                    <lb/>
                  rabole. </s>
                  <s id="s.007472">Se non lo toccherà ouero al piano dello horologio ſarà egualmente diſtante, ouero nò. </s>
                  <s id="s.007473">
                    <lb/>
                  Se ſarà egualmente diſtante, l'ombra deſcriuerà nel piano un circolo. </s>
                  <s id="s.007474">ſe non ſarà egualmente di­
                    <lb/>
                  ſtante, ma piu uicino in una parte, che nell'altra, l'ombra della cima del Gnomone deſcriuerà
                    <lb/>
                  nel piano la linea ellipſe. </s>
                  <s id="s.007475">nè ci deue sbigottire la nouità di queſti uocaboli, quando ſia in poter no
                    <lb/>
                  ſtro intendere molto bene le coſe con eſſempi materiali, però eſſorto, che con i circoli della ſpera
                    <lb/>
                  ſi proui quanto ho detto, ponendogli ſopra qualche piano con quelle portioni, che ſtanno ſopra di­
                    <lb/>
                  uerſi Orizonti, & drizzando il Gnomone, che nella cima habbia una orecchia mobile, per la qua
                    <lb/>
                  le poſſi paſſare un filo di ferro ſottile, il quale poſſi peruenire alle circonferenze de i circoli della
                    <lb/>
                  ſpera, & girarſi ſtando il ferro nella cima del Gnomone dentro l'orecchia. </s>
                  <s id="s.007476">come uedi nella ſotto­
                    <lb/>
                  poſta figura. </s>
                  <s id="s.007477">doue a. è la cima del Gnomone, con la ſua orecchia b c d. il circolo ſopra la
                    <emph.end type="italics"/>
                    <lb/>
                    <figure id="id.045.01.416.1.jpg" xlink:href="045/01/416/1.jpg" number="123"/>
                    <lb/>
                    <emph type="italics"/>
                  terra, per il quale c'imaginiamo, che il Sole ca
                    <lb/>
                  mini è f. il filo di ferro, che paſſa per l'orec­
                    <lb/>
                  chia del Gnomone, che imaginiamo, che ſia il
                    <lb/>
                  raggio del Sole. </s>
                  <s id="s.007478">& ſia il Sole nel punto e. cer
                    <lb/>
                  to è, che l'ombra del Gnomone peruenirà al
                    <lb/>
                  punto f. ſia adunque fatto iui un punto. </s>
                  <s id="s.007479">&
                    <lb/>
                  mouaſi il Sole, & peruenga al punto h. & ſi
                    <lb/>
                  milmente ſia poſto al punto e. del fil di ferro
                    <lb/>
                  in h. certo è che la punta f. toccherà un'al
                    <lb/>
                  tro punto nel piano, & ſia quello
                    <emph.end type="italics"/>
                  1.
                    <emph type="italics"/>
                  ſeguitan
                    <lb/>
                  do poi nel punto
                    <emph.end type="italics"/>
                  K.
                    <emph type="italics"/>
                  del circolo, & ponendo
                    <lb/>
                  iui il Sole, & la punta del ferro e. ſi toccherà
                    <lb/>
                  il piano dall'altra punta in l. </s>
                  <s id="s.007480">& accortandoſi
                    <lb/>
                  l'ombra piu, che il Sole s'innalza, & ſeguitan
                    <lb/>
                  do lo iſteſſo ordine ponendo il Sole in diuerſe par
                    <lb/>
                  ti di quel circolo come in m o
                    <expan abbr="q.">que</expan>
                  ſi diſegne-
                    <emph.end type="italics"/>
                  </s>
                </p>
              </subchap2>
            </subchap1>
          </chap>
        </body>
      </text>
    </archimedes>
Impressum