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# Title: Opticks: Or, A Treatise Of The Reflexions, Refractions, Inflexions and Colours Of Light (shelfmark Leibn. Marg. 193)
# Folio 95, page id 1677894601:0115
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195
2. The Proportion of the sine ot incidence to theline
et refraction ot onc and the lame fort ot rays out of onc
medium into another, is composed of the Proportion ol
che ine oE incidence to the sinc ot retraction out of the
tiest medium into aur third medium, and ot the Pro-
Portion oF the line ot incidence to the sine oF retraction
out oF thac third medium intothe lecond medium.
By the Ars Theorem the retractions of the rars ot
every Tort made out of anx medium into Air are knon
Oy havins che retraction oF the cars oF any one Cort. AS
tor instance, it the refractions ot the rays ot everr lort
out oF Rain-ater into Air be delired, let the common
Eine oF incidence out ot Citass into Air De subducted
From the fines ot refraction, and the Lxcesses will DC
7, 2753 2753 2753 272, 273, 279, 28. Suppole non
chatthe Ane ot incidence of the least retrangible rars be
eo their sine ot retraction out ot Rain water into AII 25
threc tO Four, and Car as I the difference ot thole sines
is toz the tine ot incidence, (0 is 27 the least of the
Lxcelles abore. mentioned to a Fourth number 8T; and
8+ Will De the common sion ot incidence out of Rain-
water into Air, tortrich line it vou add aIl theabore
mentioned Fixcesses vou rill have the dehired sines ot
the retractions 108, 10807. 1083, 108;, 108;, 1083,
2083, 109.
By thelatter Theorem theretraction out of onc me-
dium into another is sathered as otten as vou have
the retractions out of them both into any third medium.
AS. iF the line oF incidence of any ray out oF Cilals into
Air be to its tine ot retraction a5 20 t0 3r, and the sinc
ot incidence of the lame ray out of Air into Water, DC
te