Huygens, Christiaan, Christiani Hugenii opera varia; Bd. 1: Opera mechanica

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            quatenus licet adſueſcendum. </s>
            <s xml:id="echoid-s5834" xml:space="preserve">Hoc modo correcta ſemel len-
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            tis poſitio ad omnes obſervationes valebit. </s>
            <s xml:id="echoid-s5835" xml:space="preserve">Neque hic ſubti-
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            liter nimium objiciat quiſquam quod obliquo fili aſcenſu,
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            cum ad aſtra dirigitur, paulo minor efficitur flexus ejus à
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            gravitate ortus, quam cum filum idem horizonti parallelum
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            extenditur. </s>
            <s xml:id="echoid-s5836" xml:space="preserve">Eſt enim differentia hæc perexigua, præſertim
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            in tanta fili levitate; </s>
            <s xml:id="echoid-s5837" xml:space="preserve">& </s>
            <s xml:id="echoid-s5838" xml:space="preserve">lentium paralleliſmus, ut jam dixi-
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            mus, ad geometriæ leges exactus non requiritur.</s>
            <s xml:id="echoid-s5839" xml:space="preserve"/>
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            <s xml:id="echoid-s5840" xml:space="preserve">Multo magis ventus obeſſe dicendus foret, filum ſinuans
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            atque in latus impellens, præſertim in magnis, quas dixi-
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            mus, longitudinibus; </s>
            <s xml:id="echoid-s5841" xml:space="preserve">niſi quod tubis quoque idem ventus
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            adverſus eſt, qui concuſſu ejus tremunt ac vacillant, magno
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            ſpectantis incommodo; </s>
            <s xml:id="echoid-s5842" xml:space="preserve">ut propterea ſæpe obſervationibus
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            ſuperſedendum fuerit. </s>
            <s xml:id="echoid-s5843" xml:space="preserve">Sed quo æquiore animo hæc diſpen-
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            dia feramus, ſciendum eſt, flantibus ventis, ſemper fere
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            aëris pelluciditatem adeo turbari, etiamſi ſerenus videatur,
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            ut hoc uno omnis teleſcopiorum proſpectus impediatur;
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            </s>
            <s xml:id="echoid-s5844" xml:space="preserve">quod exercitatis ignotum eſſe nequit. </s>
            <s xml:id="echoid-s5845" xml:space="preserve">Imo & </s>
            <s xml:id="echoid-s5846" xml:space="preserve">tranquillo in-
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            terdum ac prorſus ſereno cœlo, ſcintillantibus cum maxime
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            ſideribus, fruſtra tamen teleſcopia adhibentur; </s>
            <s xml:id="echoid-s5847" xml:space="preserve">humido vapo-
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            re quodam aërem obſidente, quo fit ut ad Planetarum corpo-
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            ra reſpicienti, undatio quædam tremula & </s>
            <s xml:id="echoid-s5848" xml:space="preserve">fluctuans omnem
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            viſus aciem intercipiat. </s>
            <s xml:id="echoid-s5849" xml:space="preserve">Poſſetque, ubi hoc accidit, ipſa len-
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            tium bonitas ſuſpecta eſſe, niſi alio tempore ac puriore cœlo
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            fuiſſet cognita. </s>
            <s xml:id="echoid-s5850" xml:space="preserve">Idem vapor, ut hoc quoque obiter admo-
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            neam, non raro, lenti majori adhæreſcens, radiorum lucis
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            partem avertit: </s>
            <s xml:id="echoid-s5851" xml:space="preserve">cui malo, calefacto modice ad ignem vitro,
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            occurritur.</s>
            <s xml:id="echoid-s5852" xml:space="preserve"/>
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            <s xml:id="echoid-s5853" xml:space="preserve">Videamus nunc & </s>
            <s xml:id="echoid-s5854" xml:space="preserve">illud quod de illuſtranda lente eadem
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            diximus ad malum ſubrecta. </s>
            <s xml:id="echoid-s5855" xml:space="preserve">Quæ ſi valde procul diſtet,
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            puta ad ducentorum & </s>
            <s xml:id="echoid-s5856" xml:space="preserve">amplius pedum intervallum, vix vi-
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            detur tantum luminis, ut ab obſervatore cerni poſſit, acce-
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            ptura, etiamſi lucerna convexo vitreo juvetur, uti præcepi-
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            mus. </s>
            <s xml:id="echoid-s5857" xml:space="preserve">Sed hic intendere amplius lumen licebit, vel aucto lu-
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            cernæ ipſius ellychnio, vel latiori lente adhibita leniusque
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            convexa, quæ lucem transmiſſam, etiamſi pari </s>
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