Vitruvius Pollio, I dieci libri dell?architettura, 1567

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                  <s id="s.007659">
                    <pb pagenum="414" xlink:href="045/01/428.jpg"/>
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                  il diametro f g. nelle ſue portioni. </s>
                  <s id="s.007660">& queſto non hauemo uoluto fare nello Analemma per non
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                  confondere con la moltitudine delle linee. </s>
                  <s id="s.007661">Hora biſogna cauare dallo Analemma le altezze del
                    <lb/>
                  Sole in ogni hora per ſapere le lunghezze delle ombre. </s>
                  <s id="s.007662">Piglia dallo Analemma il meridiano a
                    <lb/>
                  b c d. & il diametro del tropico f g. partito ſecondo le diuiſioni della figura precedente ſe­
                    <lb/>
                  gnata O. & l'orizonte x e y. nel modo, che egli ſta nello Analemma. </s>
                  <s id="s.007663">& fa paſſare per le
                    <lb/>
                  diuiſioni del diametro del tropico del Cancro linee egualmente distanti all'orizonte x e y. che
                    <lb/>
                  da una parte tocchino la circonferenza del meridiano, & dall'altra il diametro del tropico f g.
                    <lb/>
                  ſegna poi nel meridiano a b c d. i numeri riportati dal diametro del tropico
                    <emph.end type="italics"/>
                  , 11. 10. 9.
                    <lb/>
                  8. 7. 6. 5. 4. 3. 2. 1.
                    <emph type="italics"/>
                  tanto di ſopra quanto di ſotto l'orizonte. </s>
                  <s id="s.007664">eſpedita questa diuiſione
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                  determinerai la lunghezza del Gnomone, & quella ponerai di ſotto dal centro e. doue s'inten
                    <lb/>
                  de eſſer la punta del Gnomone, al punto z. </s>
                  <s id="s.007665">doue s'intende, che ſia il piede del Gnomone, nel dia­
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                  metro z &. </s>
                  <s id="s.007666">che è il diametro del uerticale. </s>
                  <s id="s.007667">di modo che la lunghezza dello stile ſia e z &
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                  per lo punto z farai paſſare la línea del piano ſopra la quale ſta il Gnomone, & ſi a quella T.
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                  Z. V. per tirare adunque la lunghezza delle ombre biſogna tirare le linee dalle hore ſegnate
                    <lb/>
                  nel meridiano, che paſſino per la, cima del Gnomone, doue è la lettera e. & peruenghino alla
                    <lb/>
                  linea del piano T. Z. V. & le lunghezze delle ombre ſi miſurano dal punto z. </s>
                  <s id="s.007668">che è il pie­
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                  di del Gnomone ſopra la linea del piano. </s>
                  <s id="s.007669">come uedi qui appreſſo ſegnato. </s>
                  <s id="s.007670">& il diametro del uer­
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                  ticale ſegna nella linea del piano l'ombra della ſesta hora, che è l'hora del mezo dì. </s>
                  <s id="s.007671">poi, che egli ſi
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                  ba ritrouato le lunghezze delle ombre del tropico del cancro. </s>
                  <s id="s.007672">con la isteſſa ragione ſi piglieran­
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                  no le lunghezze delle ombre fatte quando il Sole è nel tropico del Capricorno. </s>
                  <s id="s.007673">perche egli ſi tra­
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                  ſporta la lunghezza del Gnomone dalla lettera e ſopra il uerticale, & anche ſi traſporta la li­
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                  ne a del piano ſopra laquale ſi fanno cadere le linee delle hore ſegnate ſopra il meridiano nella par­
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                  te di ſotto l'orizonte. </s>
                  <s id="s.007674">ſia adunqua e R la lunghezza del Gnomone e z poſta nel diametro del
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                  uerticale z &. </s>
                  <s id="s.007675">& ſia tirata la linea del piano S R
                    <expan abbr="q.">que</expan>
                  & dalli punti delle hore ſegnate nel
                    <lb/>
                  meridiano ſotto l'orizonte x e r. ſiano tirate linee, che paßino per lo centro e. & peruen­
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                  ghino nella linea del piano S R
                    <expan abbr="q.">que</expan>
                  & ſiano ſegnati i numeri corriſpondenti alle hore ſegnate
                    <lb/>
                  nel meridiano, & a questo modo ſi haueranno le lunghezze delle ombre fatte nelle hore del uer­
                    <lb/>
                  no. </s>
                  <s id="s.007676">& questi ſono gli anguli fatti di linee dritte dal uerticale, che ſi muoue, come hauemo detto:
                    <lb/>
                  perche il raggio del Sole dà nel diametro del uerticale, che è il Gnomone, & fa che il Gnomone
                    <lb/>
                  getta l'ombre ſopra il piano dell'horologio. </s>
                  <s id="s.007677">Cireſta hora a determinare l'arco orizontale, cioè
                    <lb/>
                  la latitudine dell'ombra, ilche ſi fa a questo modo. </s>
                  <s id="s.007678">Prima per fuggire la confuſione delle linee. </s>
                  <s id="s.007679">
                    <lb/>
                  farai il circolo a b c d. come di ſopra, nelquale ui ponerai il diametro del uerticale, z e
                    <lb/>
                  & l'orizonte x e y. il diametro del tropico f g. con le ſue diuiſioni preſe dalla figura ſegna
                    <lb/>
                  ta. </s>
                  <s id="s.007680">O. & poi farai cadere dalle diuiſioni del detto diametro del tropico f g. linee egualmente
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                  diſtanti al diametro del uerticale z e &. </s>
                  <s id="s.007681">fin ſopra l'orizonte x e y. doue noterai i nume­
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                  ri corriſpondenti a i numeri delle hore ſegnate nel diametro del tropico; & queſte linee peruenghi­
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                  no alla circonferenza del Meridiano fornito queſto anderai alla figura ſegnata O. doue ſono le
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                  diuiſioni di tutto il tropico, & comincia dalle undici ſegnate nella circonferenza, & poſto un pie
                    <lb/>
                  di del compaſſe nelle undici ſegnate nella circonferenza del tropico allargato fin alle undici ſegna
                    <lb/>
                  to ſopra il diametro di detto tropico riporterai queſta lunghezza nella figura ſeguente ſopra la li­
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                  nea delle undici hore ponendo un piede del compaſſo ſopra il punto ſegnato
                    <emph.end type="italics"/>
                  11.
                    <emph type="italics"/>
                  &
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                  1.
                    <emph type="italics"/>
                  nell'Ori­
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                  zonte x e y. & l'altro ſopra la detta linea delle undici, & nel termine farai punto
                    <emph.end type="italics"/>
                  11.
                    <emph type="italics"/>
                  Si­
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                  milmente piglia dalla figura O. la lunghezza della linea delle
                    <emph.end type="italics"/>
                  10.
                    <emph type="italics"/>
                  & riportala in queſta figu­
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                  ra ſopra la linea ſegnata
                    <emph.end type="italics"/>
                  10.
                    <emph type="italics"/>
                  & doue termina, ſegna
                    <emph.end type="italics"/>
                  10.
                    <emph type="italics"/>
                  & parimente riporterai tutte le li­
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                  nee delle hore fatte nella figura O. in queſta, ſegnando come hai fatto delle
                    <emph.end type="italics"/>
                  11.
                    <emph type="italics"/>
                  &
                    <emph.end type="italics"/>
                  1.
                    <emph type="italics"/>
                  &
                    <lb/>
                  delle
                    <emph.end type="italics"/>
                  10.
                    <emph type="italics"/>
                  &
                    <emph.end type="italics"/>
                  2.
                    <emph type="italics"/>
                  & queſto farai tanto di ſopra quanto di ſotto l'Orizonte, perche ci ſeruirà a
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                  gli archi Orizontali delle hore del uerno. </s>
                  <s id="s.007682">Hora biſogna ritrouare gli archi Orizontali, il che fa­
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                  rai a queſto modo. </s>
                  <s id="s.007683">Poni la riga nel centro e. & nel punto
                    <emph.end type="italics"/>
                  11.
                    <emph type="italics"/>
                  &
                    <emph.end type="italics"/>
                  1.
                    <emph type="italics"/>
                  ſopra la linea delle
                    <emph.end type="italics"/>
                  </s>
                </p>
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