. Of Light and Golours.

Sort, Blue ; the sixth Sort, Indigo ; and theseventh Sort, Violets which are most re-frangible, or refracted to the greatest Dis-tance from the perpendicular.

To illustrate this Matter, let GF repre-sent a Parcel of the solar Rays enteringthrough the Hole H of a Window-Shdtterl nto a darken’d Room; and there letthem fall on the Prism ABC, in the Point^: In pasting through the Prism they willhe severally refracted in a different Degree*^nd thus separated from each other, sothat at their Exit on the other Side at E,

they

Angles being constant, the Sines will be so too, orl heir Ratio to each other always the fame.

22. As by this Instrument the Angles of IncidenceRefraction are discovered, the Ratio of their Sines^s‘ll be known of coutfe, for each respective Medium,t'hus in Water the Sine of 42° is to the Sine of 30°9s 4 to 3 very nearly ; and in Glass the Sine of 46° is toSine of 30° as 3 to 2, or more nearly as 17 to xr.PJt some Experiments it has been found, that the SineIncidence is to the Sine of Refraction in DiamondS to 2.

„ 23. But since in Physical Matters we have no Autho-comparable to Sir Isaac Newton, I shall here give af a ble (from his Optics of the Proportion of the SinesIncidence and Refraction of Yellow Light (thatjctrtg nearly a Mean between the greatest and least re-fangible Rays, as we shall fee farther on). This will bestained in the first Column ; the second expresses theTensities of the Bodies estimated by their Specific Gra-• ltie s ; and the third the refractive Power of each Bodyltl r efpect of its Density.

X 2

ZO/

I

24.