Barrow, Isaac
,
Lectiones opticae & geometricae : in quibus phaenomenon opticorum genuinae rationes investigantur, ac exponuntur: et generalia curvarum linearum symptomata declarantur
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cujuſmodi quippe de cauſis diaphanum ſubinde forſan evaſurum eſt
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opacum, & </
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<
s
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echoid-s649
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xml:space
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">inſtar opaciradios valebit repercútere; </
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<
s
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echoid-s650
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xml:space
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">ceu quando lapis
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in aquam impingit obliquè; </
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>
<
s
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echoid-s651
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xml:space
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">cùm hydrargyro ſubſtracto vitrum mu-
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nitur. </
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<
s
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echoid-s652
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xml:space
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">Dum lapis _e. </
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<
s
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echoid-s653
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xml:space
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">g._ </
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<
s
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="
echoid-s654
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xml:space
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">obliquè impingit ſuperficiei EF (cui parallela
<
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OQ) per lineam AB; </
s
>
<
s
xml:id
="
echoid-s655
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xml:space
="
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">tota linea BQ ad fundum OQ protenſa
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venienti repugnabit, auxilii quoque nonnihil conferente fundo OQ;
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</
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<
s
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="
echoid-s656
"
xml:space
="
preserve
">neque mirum fuerit, ſi major hic renitentia deprehendatur, quam ubi
<
lb
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radius alter MBP perpendiculariús incurrit, quando major ſit BQ,
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quam BP.</
s
>
<
s
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echoid-s657
"
xml:space
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">] At nos ſecluſis iſtis medium velut interminatum, in om-
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nes partes æqualiter reſiſtens, abſolutè perſpicuum, & </
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>
<
s
xml:id
="
echoid-s658
"
xml:space
="
preserve
">radios ex ſe
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non reſpuens accipimus; </
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<
s
xml:id
="
echoid-s659
"
xml:space
="
preserve
">quibus ſuppoſitis perpetuò, quod dixi, ra-
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dius, obliquitate quâpiam incidentiæ nil vetante, medium denſius pe-
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netrabit. </
s
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<
s
xml:id
="
echoid-s660
"
xml:space
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preserve
">Verum in alterò caſu, cùm de medio denſiori lux rarius in-
<
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currit, non ſemper ea medium hoc permeabit. </
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<
s
xml:id
="
echoid-s661
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xml:space
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">Nam ſi magna ſatìs
<
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fuerit obliquitas; </
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<
s
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echoid-s662
"
xml:space
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">ſubinde radius inflexus ſupra ſuperficiem EF at-
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tolletur, angulúſque (qui dicitur) refractus, aut inflexus rectum ex-
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ſuperabit; </
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<
s
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echoid-s663
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xml:space
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">quinimò fieri poteſt ut ipſum exæquet. </
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<
s
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echoid-s664
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xml:space
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">Sit in exemplum
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primò inclinatio graduum 45, vel ſemirecta; </
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<
s
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xml:space
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preserve
">Et ZB ad ZD ſe habe-
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at ut quadrati diameter ad ſuum latus quæ fermè proportio radiorum
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ex aqua in aerem tranſeuntium, experientiâ conteſtante, rationem
<
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/>
<
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xlink:label
="
note-0035-01
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xlink:href
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xml:space
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">Fig. 12.</
note
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metitur) radius velut in ipſam EF refringetur, aut eam ſtringens pro-
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cedet. </
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<
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xml:space
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">Eſt enim Z δ (æqualis ipſi ZD) jam ad EF perpendicularis,
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adeoque δ κ arcum δ D contingens ipſi EF congruet. </
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<
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xml:space
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">Unde patet
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obiter, id quod ſuperiùs inſinuatum, non univerſim conſtare, quòd
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radius à quo loco medii unius in aliud proceſſit, ad eundem retrogra-
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dus accedet. </
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<
s
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xml:space
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">Hoc enim ſaltem in caſu radius AB refringitur in β α ſu-
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perficiei media dirimenti parallelam; </
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<
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">veruntamen qui per α β progre-
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ditur minjmè recedet ad BA, nec ullam, ut manifeſtum eſt, omninò
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refractionem patietur. </
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<
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xml:space
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">Sed hic caſus tantùm unus, & </
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<
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">quaſi pro nullo
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cenſeri poteſt. </
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<
s
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xml:space
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">Quod ſi, ſervatâ quoad denſitatem eâdem proportione,
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<
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xlink:label
="
note-0035-02
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note-0035-02a
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xml:space
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">Fig. 13.</
note
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radius AB paullò magis ad rectam EF inclinetur, ejus. </
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<
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">Refractus
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ſupra ipſam EF aſſurget; </
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<
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">punctum quippe D rectam EF nunquam
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pertinget; </
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xml:space
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">& </
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<
s
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xml:space
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">punctum B decurſâ rarius intra medium peripheriâ
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B β in denſum remeabit; </
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<
s
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xml:space
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">in quo proinde rurſus, circulatione ſuâ di-
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miſſà, per tangentes β α, δ κ ferentur; </
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<
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">adeò quidem ut radius ABCD
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jam reflecti videatur, quatenus medium denſius haud penetrat totus,
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vel egreditur.</
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</
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<
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">VI. </
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">Nec ineptè quidem (etſi quodammodò, velutíque primariò, ſit
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refractio) reflectionis nomen adſciſcit hæc actio, quatenus & </
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