Of Light and Colours.

face; which is the Cafe of all Glasses soli-a ted or quickfilver’d. Whence it appears,that the Light reflected from the first Sur-face bears a very small Proportion to that^hich is transmitted into the Substance ofGlass.

When a Ray of Light, as HC, passes^ut of Air into a denser Medium, as ABFO,will be strongly attracted by the Particles°f the Surface of the Medium A B a littleVv ay on each Side ; the Consequence where-°f is, that its Motion will be accelerated atthe Entrance of the Medium, and its Di-rection somewhat altered ; for since the At-^action of the Medium is perpendicular to"8 Surface, it will deflect or bend the Rayof its first Direction H F, into a new oneE E (through the Medium) which lies nearer'to the Perpendicular KD, drawn through*he Point of Incidence C : And this is calledthe Refraction of a Ray of Light ; HCKthe Angle of Incidence, and D C E the^Rgle of Refraction.

If on the Point C be described a Circle^HRG, and from the Points H and GInhere the Circle cuts the Incident refractedbe drawn the Lines H L, GI, at RightAngles to the Perpendicular K D, they willthe Sines of the Angles of Incidence and

Refraction ,

297

PlateXXXIV,Fig. 8.