on friction as a source of heat, 189; determination of the mechanical equivalent of heat, 192. Rumford Medal, foundation of the, 167; recipients of the, 167; awarded to Fresnel, 233; awarded to Clerk Maxwell, 297. Rumford roaster, 166. S. "Sandford and Merton," influence of, on the negro traffic, 197. Saturn's rings, Maxwell's essay on, 285. Sea-water, resistance of, 142. Seguin's attempt to measure loss of heat in the steam-engine, 323. Self-induction, effect of, on sudden discharge, 142; of electro-magnet, 268; effect of, in induction coil, 321. Sensation of heat, cause of, 33. Seraphic love, Boyle's essay on, 15. Shaw's, Dr., comments on Boyle, 37. Snellius's laws of refraction, 1. Socratic method adopted by Franklin, 44. Specific inductive capacity, discovered by Cavendish, 139; rediscovered by Faraday, 272. Spectral colours, mixed by Boyle, 31; mixed by Maxwell, 297. S.P.G., foundation of the, 30. Spheroidal waves in Iceland-spar explained by Young, 226. Stamp Act, 112. Standards Commission, report of, 232. Statistical method, Maxwell's, 299. Steeple struck by lightning at Newbury, 92. Stereoscope, Maxwell's real-image, 298. Stokes's, Professor G. G., exhibition of the bright centre in the shadow of a disc, 222. Suction caused by atmospheric pressure, 29. Surface-tension, 228; suggested by Segner, 229; Young's investigations on, 229. T. Table of results of experiments on Boyle's law, 27. Tatum's lectures on natural philosophy, 240. Telephone, Graham Bell's, 319. Temperature, its nature, 33. Thermometers first hermetically sealed, 2. Thomson's, Professor James, application of the principle of dissipation of energy to the freezing of water under pressure, 327. Thomson's, Sir William, statement of the principle of dissipation of energy, 327; vortex theory of matter, 312; mirror galvanometer, 313; replenisher, 316. Thunder-storms, Franklin's theory of, 81. Torpedo, Cavendish's experiments on the, 140; Davy's experiments on the, 251. Traction of carriages, Rumford's experiments on, 189. Trial plate used by Cavendish, 139. Tyres, relative advantages of broad and narrow, 189. U. Undulatory theory founded by Hooke and Huyghens, 218. Union of the American States, Franklin's plan for, 68. University of Philadelphia, foundation of the, 64. V. Vacuum, Boyle's argument on the cause of a, 23. Velocity of electricity, 93; of light measured by Roemer, 2; of light deduced from electro-magnetic theory, 306. Viscosity of gases explained by Maxwell, 299. Voltaic pile constructed by Faraday, 241. Vortex theory of matter, 312. Voss machine, 316. W.