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# Title: [Lectiones XVIII, Cantabrigiae in Scholis publicis habitae] Lectiones XVIII, Cantabrigiæ in Scholis publicis habitæ (shelfmarks Leibn. Marg. 0; ZEN Leibn. Marg. 0)
# Folio 17, page id 797435492:0033
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E. P C F. I.
cujusmodi quippe de causis diaphanum subinde Fortan ératurum est
opacum, e inctar opaci radios ralebir repercutere; ceu quando lapis
in aquam impinsie oblique; cum hydrarorro substracto vicrum mu-
nitur. Dum lapis e. e. Oblique impinsir superficiei P F (cui parallela
OO) per lineam AB; tora linea B O ad Fundum OO prorensa
renienti repugnabir, auxilii quoque nonnihil conferente fundo O:
nequemirum fuerit, si major hic renitentia deprehendatur, quam ubi
radius alter M B P perpendicularius incurrit, quando major sicBC
quam BP. ) AEnos scclusis ictis medium velut interminatum, in om-
nes partes aequaliter resistens, absolure perspicuum, e radios ex se
non respuens accipimus; quibus suppolitis perpetuo, quod dixi, ra
dius, obliquirate quapiam incidentix nil recante, medium densius pe-
nerrabit. Verum in alrero casu, cum de medio densiori lux rarius ir-
currit, non semper ea medium hoc permeabie. Nam Si magna PatiS
Fuerit obliquitas; Tubinde radius inflexus supra Cuperficiem E F at-
colletur, anguluisque (qui dicitur) retractus, aue inAlexus rectum ex
superabit; quinimo fieri pocest ue iptum exxquet. Sit in exemplum
primo inclinario graduum 45, rel semirecta, FFZ B ad Z D sc habe-
ac ut quadrari diamerex ad luum lacus, qua ferme provortio radiorum
ex aqua in aerem cranseunium, experientia conteltance, rationem F15. 12o
metitur) radius relut in ipsam P F retringetur, aue eam Aringens pro-
cedet. Fst enim Z S (xqualis ip(IZ D) jam ad F F perpendicularis,
adeoque s’n arcum sD continsens ipsi P F congruer. Unde patet
obitei, id quod superius inlinuacum, non univerlim constare quod
radius a quo loco medii unius in aliud processit, ad eundem retrosra-
dus accedet. Hloc enim Caltem in casu radius A B retrinsitur in 6 ae lu-
perticieimedia dirimenti parallelam; veruntamen qui per a 6 proore-
dicur minime recedet ad B A, nec ullam, uc manifectum est, omnino
refractionem patietur. Sed hic casus tantum unus, ex quasi pro nullo
censeri porest. Duod (i, serratâ quond densitarem eadem proportione,
radius AB paullo masis ad rectam P F inclinetur, ejus. Retractus F18. 23.
supra iplam E F alturset; punctum quippe D rectam P. F nunquam
pertinser; _ punctum B decurla rarius intra medium peripheria
BCindensum remeabit; in quo proinde rurlus, circulatione sua di-
missi, per tangentes 6 a, sn Fereneur; adeo quidem ue radius ABCD
jam reflecti videatur, quatenus medium denlins hand penetrar cotuS,
vel egreditur.
VI. HecMepte qudem (etss quodammodo, relurique primario, EiE
retractio) retlectionis nomen adsciscir haec a lio, guatenus ex ipla
refectionis