Barrow, Isaac
,
Lectiones opticae & geometricae : in quibus phaenomenon opticorum genuinae rationes investigantur, ac exponuntur: et generalia curvarum linearum symptomata declarantur
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<
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<
s
xml:id
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echoid-s897
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xml:space
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">Pro refractione vero: </
s
>
<
s
xml:id
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echoid-s898
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xml:space
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">Incidat radius AB medio EF in B; </
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>
<
s
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echoid-s899
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xml:space
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">& </
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<
s
xml:id
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echoid-s900
"
xml:space
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preserve
">iſthic
<
lb
/>
refringatur in B _a_ dico permutatim radium _a_ B regredientem in BA
<
lb
/>
refringi. </
s
>
<
s
xml:id
="
echoid-s901
"
xml:space
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preserve
">Nam per occurſum B ducatur QBP media dirimenti EF
<
lb
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<
note
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="
left
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xlink:label
="
note-0042-01
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xlink:href
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note-0042-01a
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xml:space
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">Fig. 20.</
note
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perpendicularis; </
s
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<
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echoid-s902
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xml:space
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">& </
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<
s
xml:id
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echoid-s903
"
xml:space
="
preserve
">in hac utcunque ſumpto puncto P ducatur PG
<
lb
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ad AB protractam perpendicularis, ut & </
s
>
<
s
xml:id
="
echoid-s904
"
xml:space
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">PH ad B _a_; </
s
>
<
s
xml:id
="
echoid-s905
"
xml:space
="
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">& </
s
>
<
s
xml:id
="
echoid-s906
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xml:space
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">produca-
<
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tur _a_ BS. </
s
>
<
s
xml:id
="
echoid-s907
"
xml:space
="
preserve
">Eſt ergo PG ſinus rectus anguli incidentiæ ABQ ad
<
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radium BP; </
s
>
<
s
xml:id
="
echoid-s908
"
xml:space
="
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">& </
s
>
<
s
xml:id
="
echoid-s909
"
xml:space
="
preserve
">PH ſinus anguli refracti QBS ad eundem radium
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BP. </
s
>
<
s
xml:id
="
echoid-s910
"
xml:space
="
preserve
">Cùm ìtaque ratio PG ad PH refractionem metiatur è ſuperiori
<
lb
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medio factam in inferius; </
s
>
<
s
xml:id
="
echoid-s911
"
xml:space
="
preserve
">etiam viciſſim rectarum PH, PG propor-
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tio refractionem determinabit ab inferiori medio factam in ſuperius.
<
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/>
</
s
>
<
s
xml:id
="
echoid-s912
"
xml:space
="
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">Unde ſi radius _a_ B jam ponatur incidens; </
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>
<
s
xml:id
="
echoid-s913
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xml:space
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">cùm ſint PH, PG recti ſi-
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nus anguli incidentiæ PBH, & </
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<
s
xml:id
="
echoid-s914
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xml:space
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">anguli PBG, liquidum eſt ipſam HB
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in BA refringi.</
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<
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xml:id
="
echoid-s915
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</
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<
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xml:space
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">IV. </
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<
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xml:space
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">Angulo incidentiæ majori major competit angulus inflexus.
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</
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<
s
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echoid-s918
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xml:space
="
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">(Angulum inflexum vocito, qui à perpendiculari continetur & </
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<
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xml:id
="
echoid-s919
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xml:space
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">in-
<
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flexo; </
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>
<
s
xml:id
="
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xml:space
="
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">is proinde reſpectivè dicitur angulus reflexus, vel refractus. </
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<
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echoid-s921
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<
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Angulus autem inflectionis (hoc eſt reflectionis reſpectivè, vel refracti-
<
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onis) appellatur is, qui comprehenditur ab incidente & </
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<
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xml:space
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">inflexo; </
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<
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xml:id
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echoid-s923
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xml:space
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">inci-
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dentiæ verò, nè quis ſecùs accipiat, apud nos angulus eſt, quem con-
<
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tinent incidens & </
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>
<
s
xml:id
="
echoid-s924
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xml:space
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">perpendicularis.) </
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<
s
xml:id
="
echoid-s925
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xml:space
="
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">Quod propoſitum ſpectat effatum,
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id è poſitis principiis manifeſtè conſectatur. </
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<
s
xml:id
="
echoid-s926
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xml:space
="
preserve
">Etenim in reflectione
<
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ipſi anguli reflexi angulis incidentiæ proportionales ſunt; </
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>
<
s
xml:id
="
echoid-s927
"
xml:space
="
preserve
">in refracti-
<
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one ſaltem recti ſinus angulorum refractorum ſinubus angulorum in-
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cidentiæ proportionantur. </
s
>
<
s
xml:id
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echoid-s928
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xml:space
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">Unde liquido conſtat propoſitum: </
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<
s
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echoid-s929
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xml:space
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">quorſum
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verba, quorſum Schemata multiplicem?</
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<
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</
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<
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xml:space
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">V. </
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<
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xml:space
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">Cùm incidentes ad ſuperficiem mediam ſeſe decuſſant, iidem
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ſeſe inflectionem paſſi decuſſabunt, eodem ordine ſervato, quem directè
<
lb
/>
progedientes habuiſſent (utique ſic ut perpendiculari poſt inflectionem
<
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propior incedat qui propior antea fuit.)</
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<
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</
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<
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<
s
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xml:space
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">Hæc propoſitio reverà non differt à præcedente; </
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<
s
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xml:space
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">quò demirer
<
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<
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xlink:label
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note-0042-02
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xlink:href
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xml:space
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">_Herig. Diop. 8_.</
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eam à non nemine principia noſtra uſurpante aliunde compro-
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bari.</
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</
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<
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">VI. </
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<
s
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echoid-s938
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xml:space
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">Angulo incidentiæ majori major convenit angul@s inflectionis.
<
lb
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</
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<
s
xml:id
="
echoid-s939
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xml:space
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">Quoad refiectionem, res extra dubium evidens eſt; </
s
>
<
s
xml:id
="
echoid-s940
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xml:space
="
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">angulus enim refle-
<
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ctionis incidentiæ majori conveniens eum planè continet, qui minori
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incidentiæ reſpondet. </
s
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<
s
xml:id
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echoid-s941
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xml:space
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">Pro refractione vero: </
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<
s
xml:id
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echoid-s942
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xml:space
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">ſit recta QBP refrin-
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genti perpendicularis; </
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>
<
s
xml:id
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xml:space
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">incidant autem radii ABG, DBH (ſcilicet </
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