h ( R g1 t1 ) ) ( ) ) i ( I u1 ) ) ( ) ) j ( v1 )→ B1 ) ) ) k ( w1 ) ) ( J ) ) l ( w1 ) ) a = Rays falling on water, specula, &c. b = Rays passing through water, glass, &c. Measures. Ptolemy. c = Colours seen by prisms, in rainbow, &c. d = Colours in diff. transp. Substances. Optical instrum^ts. e = Two Images in Rhomb. of Calcspar. f = Two Images in other crystals. g = Two Rhombs of Calcspar make 4 images alternately appear and disappear. h = Fringes of shadows. Grimaldi. Hook. Newton. i = Spectra of gratings. Fraunhofer. j = Colours of striated surfaces. Coventry's Micromet^r. Barton's Buttons. Young. k = Colours of _thick Plates_. Newton. l = Colours of _thin Plates_. Hook. Newton. m = Euclid. Ang. Inc. equals Ang. Reflection. n = Snell. Sin. Refr. to Sin. Inc. in giv. _Ratio_ in same med. o = By measures of Refraction. p = Dispersion of colours is same when Refr. is diff. Measures. Dollond. q = Huyghens. Rays of light have four Sides with regard to which their properties alternate. Newton. Idea of _Polarization_ introduced, which governs subsequent observations. _Dipolarization_ with Colours. r = Newt. Refr. R^o. is diff. for diff. colours, but in same med. is const. for each colour. s = Measures. Huyghens. t = Double Refr. in biaxal crystals. Brewster. u = Rays are polarized by Calcspar, Quartz, &c. v = Rays are polarized by biaxal crystals. w = Rays are polarized by Tourmaline, Agate, &c. x = Rays are polarised by Refl. at glass. y = Rays are polarized by transmission through glass. z = Variable q^y. of pol. refl. light paral. plane of Refl. Arago. A = Variable q^y. of pol. refl. light perp. plane of Refl. B = Whole light reflected by internal Refl. C = Pol. Rays through uniaxal crystals give colours. Rings. Wollaston. D = Pol. Rays through biaxal crystals give colours. Arago. E = Pol. Rays. through imperf. crystallized bodies give colours. (Glass strained, jellies prest.) Brewster. F = Pol. Rays in axis of Quartz give a peculiar set of colours. Plane of Pol^n twisted diff^ly. for diff. colours. Biot. Arago. G = Pol. Rays oblique in Quartz give peculiar rings, &c. H = Pol. Rays through certain liquids give a peculiar set of colours. I = The Laws of these Phænomena were never discovered till Theory had indicated them. J = _Newton's Scale of Colours._ _Fits_ of Rays. Newton. K = Dollond. L = Prop^n of Ref. R^s is diff. in diff. med. _Achromatism_. M = Huygh^s. Law of Double Ref. exp. by a spheroid. N = Change of plane of pol. by Refl. Arago O = Light is _circularly pol._ by 2 Refl. in _Fresnel's Rhomb._ Fresnel.