INDEX TO THE PRECEDING PAVER. N.B. The figures refer to the articles, the letter* to the uritjintil mt pp. 400—407. Absorbing and reflecting power, determination of, with respect to invisible rays, 194—196, 201—204, Absorption, on the cause of, 237, 238; connexion of, with internal dispersion, 59, 60, 63, 71, 70, 120, 126, 146, 148. Air expelled from water, 172. Appearance of highly sensitive media, 27, 29, 164. Archil, 65-—71. Canary glass, 73—77, F. Chemical applications of internal diH-pcrsion, 67—70, 205—214. Clearness of sensitive fluids accounted for, 86. Coloured glasses, fundamental exi>eri-ment with, 7; nature of the blue reflexion in orange glasses, 7(.); examined for dispersion, 167, KiH. Colourless glasses, internal diBperwon in, 78; defect of transparency of, 22, 202, 217—219, A. Colours of natural bodies, 174-......17H. Concentration and dilution, effect of, 185—188. Crystals, natural, 165, 166 (see Fluor-spar, Uranium). Datura stramonium, solution, 43; paper, 95; capsules, 117. DisperBion, true and false, defined, 25; distinguished, 26, 21); cautions, 100- -173; usual features of true, 44—4(>; on the cause of true, 226—-236; nature of false, 179; instances, 181; applications, 180, 182. Epipolic dispersion, 1; explanation of, 6. Esculine, 31, 212. Explanation of terms, 21—30, 101. Eye, opacity of the, 220, K. Fixed lint's of the inviniMo rays, exhibited, 16; deHc;ription of the, 21 23, A, II; effect of viewing through a prism the fixed linen «ho\vn by meana of HOUHitive media, 17, Hi) 93, 1(K). FlameH, effect of varioUH, 197 —200. Fluor-Hpar, 32 36. Groundsel, petain of the purple, 120. Guaiacum, solution, 37 41; washed paper, i)H; .solution of, mied UK a tent object, 200. Heat, effect of, on the sensibility- of ghlKH, d'C., 1HL Horse-chi.'Htnut, 31, 212. Illuminating power of the highly refrangible niys, loi, It),"., 11. Internal diHper.sion, 2. Lavender rays, !().">, B. Leuf-Krecn, absorption, 47 -VJ; internal dispersion, .13 111, '.17, IIK, 121. Litfhtnintf, elTect of, J. Linear KpKilrum, 107 1011; mudta obtained with u, 113 KM"*, iVt;. List of highly Hen:, 23<;. Pennanf.anate of polansa, abi-orjitinn, I). Phosphorescence compared with internal dispersion, 220 225. Phosphoro^enic rays of an electric . park, nature of the, 219 221, A. Polarisation, absence of, in di: prrnrcl li^lit, 1, h">; of the incident, ray:* a matter of indifi'ercucr, 20,