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Refraction be created out of Air into Water, the sin of Incidence of the red light-weight is to the sin of its Refraction as four to three. If out of Air into Glafs, the Sines square measure as I7 to II. In light-weight of alternative colors the Sines produce other Proportions: however the distinction is FO very little that it want feldom be confidered.
Suppofe so, that R S [ in Fig. I. ] repre-fents the Surface of ftagnating Water, which C within the purpose of Incidenec within which any Ray coming back within the Air from A within the Line A C is mirrored or refracted, and that i would understand whither this Ray fhall follow Reflexion: I erectupon the Surface of the Water from the purpose of Incidence the Perpendicular C P and turn out it downwardly to letter, and conclude by the firft Axiom, that the Ray when Reflexion and Re-fraction, Fhall be Found fomewhere within the Plane of the Angle of Incidence A C P made.
I Let fall so upon the Perpendicular C P the sin of Incidence A D; and if the mirrored Ray be defired, I turn out A D to B of that decibel be adequate to AD, and draw C B.
For this Line C B Fhall be the mirrored Ray; the Angle of Reflexion B C P and its sin B D being e-qual to the Angle and sin of Incidence, as they got to be by the fecond Axiom.
however if the refracted Ray be defired, I turn out A D to H, FO that D H is also to A D because the sin of Re-fraction to the sin of Incdence, that's ( if the sunshine be red ) as three to 4; and concerning the middle C and within the Plane A C P with the Radius C A defcribing a Circle A BE, I draw Parallel to the Perpendicular C P letter the road H E cutting the
Circun-
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