Newton, Isaac, Philosophia naturalis principia mathematica, 1713

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                  <s>
                    <pb xlink:href="039/01/500.jpg" pagenum="469"/>
                  planis Orbium Cometarum per Solem tranſeuntibus jacentes, de­
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                    <arrow.to.target n="note498"/>
                  viant ab oppoſitione Solis in eas ſemper partes, quas capita in
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                  Orbibus iilis progredientia relinquunt. </s>
                  <s>Quod ſpectatori in his
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                  planis conſtituto apparent in partibus a Sole directe averſis; di­
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                  grediente autem ſpeſtatore de his planis, deviatio paulatim ſen­
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                  titur, & indies apparet major. </s>
                  <s>Quod deviatio cæteris paribus
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                  minor eſt ubi cauda obliquior eſt ad Orbem Cometæ, ut & ubi
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                  caput Cometæ ad Solem propius accedit; præſertim ſi ſpectetur
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                  deviationis angulus juxta caput Cometæ. </s>
                  <s>Præterea quod caudæ
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                  non deviantes apparent rectæ, deviantes autem incurvantur. </s>
                  <s>Quod
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                  curvatura major eſt ubi major eſt deviatio, & magis ſenſibilis ubi
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                  cauda cæteris paribus longior eſt: nam in brevioribus curvatura
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                  ægre animadvertitur. </s>
                  <s>Quod deviationis angulus minor eſt juxta
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                  caput Cometæ, major juxta caudæ extremitatem alteram, atque
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                  adeo quod cauda convexo ſui latere partes reſpicit a quibus ſit
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                  deviatio, quæQ.E.I. recta ſunt linea a Sole per caput Cometæ in
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                  infinitum ducta. </s>
                  <s>Et quod caudæ quæ prolixiores ſunt & latiores,
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                  & luce vegetiore micant, ſint ad latera convexa paulo ſplendi­
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                  diores & limite minus indiſtincto terminatæ quam ad concava. </s>
                  <s>
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                  Pendent igitur Phænomena caudæ a motu capitis, non autem a
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                  regione cœli in qua caput conſpicitur; & propterea non fiunt per
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                  refractionem cœlorum, ſed a capite ſuppeditante materiam ori­
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                  untur. </s>
                  <s>Etenim ut in Aere noſtro fumus corporis cujuſvis igniti
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                  petit ſuperiora, idque vel perpendiculariter ſi corpus quieſcat,
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                  vel oblique ſi corpus moveatur in latus: ita in Cœlis ubi corpora
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                  gravitant in Solem, fumi & vapores aſcendere debent à Sole (uti
                    <lb/>
                  jam dictum eſt) & ſuperiora vel recta petere, ſi corpus fumans
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                  quieſcit; vel oblique, ſi corpus progrediendo loca ſemper deſerit
                    <lb/>
                  a quibus ſuperiores vaporis partes aſcenderant. </s>
                  <s>Et obliquitas iſta
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                  minor erit ubi aſcenſus vaporis velocior eſt: nimirum in vicinia
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                  Solis & juxta corpus fumans. </s>
                  <s>Ex obliquitatis autem diverſitate
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                  incurvabitur vaporis columna: & quia vapor in columnæ latere
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                  præcedente paulo recentior eſt, ideo etiam is ibidem aliquanto
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                  denſior erit, lucemque propterea copioſius reflectet, & limite mi­
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                  nus indiſtincto terminabitur. </s>
                  <s>De Caudarum agitionibus ſubita­
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                  neis & incertis, deque earum figuris irregularibus, quas nonnulli
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                  quandoQ.E.D.ſcribunt hic nihil adjicio; propterea quod vel a
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                  mutationibus Aeris neſtri, & motibus nubium caudas aliqua ex
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                  parte obſcurantium oriantur; vel forte a partibus Viæ Lacteæ,
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                  quæ cum caudis prætereuntibus confundi poſſint, ac tanquam ea­
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                  rum partes ſpectari. </s>
                </p>
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        </body>
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