Newton, Isaac, Philosophia naturalis principia mathematica, 1713

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                <pb xlink:href="039/01/502.jpg" pagenum="471"/>
                <p type="main">
                  <s>Quo temporis ſpatio vapor a capite ad terminum caudæ aſcen­</s>
                </p>
                <p type="main">
                  <s>
                    <arrow.to.target n="note500"/>
                  dit, cognoſci fere poteſt ducendo rectam a termino caudæ ad So­
                    <lb/>
                  lem, & notando locum ubi recta illa Trajectoriam ſecat. </s>
                  <s>Nam
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                  vapor in termino caudæ, ſi recta aſcendat a Sole, aſcendere cœpit
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                  a capite quo tempore caput erat in loco interſectionis. </s>
                  <s>At vapor
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                  non recta aſcendit à Sole, ſed motum Cometæ, quem aute aſcen­
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                  ſum ſuum habebat, retinendo, & cum motu aſcenſus ſui eundem
                    <lb/>
                  componendo, aſcendit oblique. </s>
                  <s>Unde verior erit Problematis
                    <lb/>
                  ſolutio, ut recta illa quæ Orbem ſecat, parallela ſit longitudini
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                  caudæ, vel potius (ob motum curvilineum Cometæ) ut eadem a
                    <lb/>
                  linea caudæ divergat. </s>
                  <s>Hoc pacto inveni quod vapor qui erat in
                    <lb/>
                  termino caudæ
                    <emph type="italics"/>
                  Jan.
                    <emph.end type="italics"/>
                  25, aſcendere cœperat a capite ante
                    <emph type="italics"/>
                  Dec.
                    <emph.end type="italics"/>
                  11,
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                  adeoque aſcenſu ſuo toto dies plus 45 conſumpſerat. </s>
                  <s>At cauda
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                  illa omnis quæ
                    <emph type="italics"/>
                  Dec.
                    <emph.end type="italics"/>
                  10 apparuit, aſcenderat ſpatio dierum illo­
                    <lb/>
                  rum duorum, qui a tempore Perihelii Cometæ elapſi fuerant. </s>
                  <s>
                    <lb/>
                  Vapor igitur ſub initio in vicinia Solis celerrime aſcendebat, &
                    <lb/>
                  poſtea cum motu per gravitatem ſuam ſemper retardato aſcen­
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                  dere pergebat; & aſcendendo augebat longitudinem caudæ: cauda
                    <lb/>
                  autem quamdiu apparuit ex vapore fere omni conſtabat qui a
                    <lb/>
                  tempore Perihelii aſcenderat; & vapor, qui primus aſcendit, &
                    <lb/>
                  terminum caudæ compoſuit, non prius evanuit quam ob nimiam
                    <lb/>
                  ſuam tam a Sole illuſtrante quam ab oculis noſtris diſtantiam vi­
                    <lb/>
                  deri deſiit. </s>
                  <s>Unde etiam caudæ Cometarum aliorum quæ breves
                    <lb/>
                  ſunt, non aſcendunt motu celeri & perpetuo a capitibus & mox
                    <lb/>
                  evaneſcunt, ſed ſunt permanentes vaporum & exhalationum co­
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                  lumnæ, a capitibus lentiſſimo multorum dierum motu propagatæ,
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                  quæ, participando motum illum capitum quem habuere ſub initio,
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                  per cœlos una cum capitibus moveri pergunt. </s>
                  <s>Et hinc rurſus col­
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                  ligitur ſpatia cœleſtia vi reſiſtendi deſtitui; utpote in quibus non
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                  ſolum ſolida Planetarum & Cometarum corpora, ſed etiam rariſ­
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                  ſimi caudarum vapores motus ſuos velociſſimos liberrime peragunt
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                  ac diutiſſime conſervant. </s>
                </p>
                <p type="margin">
                  <s>
                    <margin.target id="note500"/>
                  LIBER
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                  TERTIUS.</s>
                </p>
                <p type="main">
                  <s>Aſcenſum caudarum ex Atmoſphæris capitum & progreſſum in
                    <lb/>
                  partes a Sole averſas
                    <emph type="italics"/>
                  Keplerus
                    <emph.end type="italics"/>
                  aſcribit actioni radiorum lucis ma­
                    <lb/>
                  teriam caudæ ſecum rapientium. </s>
                  <s>Et auram longe tenuiſſimam in
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                  ſpatiis liberrimis actioni radiorum cedere, non eſt a ratione pror­
                    <lb/>
                  ſus alienum, non obſtante quod ſubſtantiæ craſſæ, impeditiſſimis
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                  in regionibus noſtris, a radiis Solis ſenſibiliter propelli nequeant. </s>
                  <s>
                    <lb/>
                  Alius particulas tam leves quam graves dari poſſe exiſtimat, &
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                  materiam caudarum levitare, perque levitatem ſuam a Sole aſcen-</s>
                </p>
              </subchap2>
            </subchap1>
          </chap>
        </body>
      </text>
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