Equilibrium, 154. Etiolation, 180. Fermentation, 183. Food, 145. Force, vital, whence derived, 171. physical, 194. chemical, 194. of chemical affinity, 53. of cohesion, 51. Force, mechanical or molar, 205. molecular, 205. Friction, 35. Heat, absorbed, changed into chemical separation, 114. into electrical separation, 115. into electricity in motion, 116. Heat-units of different substances, 119. Heat-motion, 80. Heat-engines, their essential conditions, 107. Helmholtz, 141. Heraclitus on energy, 133. Herbivora, 191. Heterogeneity essential in electrical development, 64. Huyghens, 137. Hydraulic press, 32. Inclined plane, 28. Incubation, 186. Individuals, our ignorance of, 1. Induction, electric, 65. of electric currents, 75. Instability, mechanical, 155. chemical, 156. Intellectual labor, 234. Joule, 137, 140, 141. Joule’s experiments on work and heat, 44. Kilogrammetre, 16. Larva, 187. Latent heat, 57. Laws of conservation, 82. Life depends on the sun, 165. Light, a perpetual, impossible, 149. Lime, carbonate, easily decomposed, 58. List of energies, 78-82. Machines, their true function, 33. animated and inanimate, 157. Magnets, attachment and repulsion of, 75. Maxwell, 141. Mayor, 140. Mechanical energy changed into heat, 23. equivalent of heat, 43. force, 205. instability, 155. Mental forces, mutual correlations of, 227-236. Mind, its correlations to natural forces, 218-227. and body, 207, 211. Molar force, 205. Molecular attraction and heat, 55. separation, 80. Molecules, ultimate, of matter, 5. their motions, 7. and atoms, 51. Motion changed into an electric current, 99. Muscular power, 207. Narcotic stimulants, 229. Negative and positive electricity, 63. Nerve power, 207. Newton, 136, 137. Non-conductors of electricity, 61. Percussion, 36. Perpetual motion, 139. Physical force, 194. Plants growing at night, 181. Positive and negative electricity, 63. Protoplasm, 177. Pulleys, their function, 30. Radiant energy, 81. converted into absorbed heat, 123. promoting chemical separation, 123. Rankine, 141. Resinous and vitreous electricity, 63. Rotation of earth retarded, 95. Rumford, 39, 137. Silver oxide readily decomposed, 58. Solar rays, decomposition by, 59. Sulphur, 146. Sun--a source of high-temperature heat, 148. Sun’s heat, origin of, 150. spots, auroras, and cyclones correlated, 98. Tait, 141. Temperature of dissociation, 115. Thermo-electricity, 116. Thermopile, 117. Thomas Aquinas, 209. Thomson, William and James, 140. Tides, 146. Tissues, decay of, 164. Universe, its probable fate, 152. Units of heat and work, 46. Vegetation, 176. Velocity and energy, relation between, 16.