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[page 13] One of theſe Parts [of a piece of black paper] I painted vvith a red Colour and the other vvith a blevv. […] This Paper I vievved through a Priſm of ſolid Glaſs, vvhoſe tvvo Sides through vvhich the Light paſſed to the Eye vvere plane and vvell poliſhed, and contained an Angle of about Sixty Degrees: vvhich Angle I call the refracting Angle of the Priſm. […] [page 17] Theſe Experiments may ſuffice for the Colours of Natural Bodies. For in the Colours made by the Refraction of Priſms this Propoſition vvill appear by the Experiments vvhich are novv to follovv in the next Propoſition.