Liquefaction, latent heat of, 178. Liquid, efflux, law of, 150; equilibrium, figures of, 4 et seq.; the latter produced in open air, 7-8; their beauty and multiplicity of form, 7, 8; made permanent by melted colophonium, 7. Liquids, forms of, 1-16; difference between, and solids, 2; their mobility and adaptiveness of form, 3; the courtiers _par excellence_ of the natural bodies, 3; possess under certain circumstances forms of their own, 3. Living force, 137, 184; law of the conservation of, 149. Lloyd, observation of the conical refraction of light, 29. Lobster, of Lake Mohrin, the, 61. Localisation, cerebral, 210. Locke, on language and thought, 358. Locomotive, steam in the boiler of, 219. Loeb, J., 289, 291, 302. Logarithms, 195, 219; in music, 103-104. Logical root, of the principle of energy, 181; of the principle of excluded perpetual motion, 182. Lombroso, 280. Lucian, 347. _Macula acustica_, 272. Magic lantern, 96. Magic powers of nature, 189. Magical power of science, belief in the, 189. Magnet, a, 220; will compared to the pressure of a, 14; coercive force of a, 216. Magnetic needle, near a current, 207. Magnetised bar of steel, 242-243. Major and minor keys in music, 100 et seq. Malus, 242. Man, a fragment of nature's life, 49; his life embraces others, 234. Mann, 364. Manuscript in a mirror, 93. Maple syrup, statues of, on Moon, 4. Marx, 35. Material, the relations of work with heat and the consumption of, 245 et seq. Mathematical methods, their character, 197-198. Mathematics, economy of, 195; on instruction in, 338-374; C. G. J. Jacobi on, 280. Matter, constancy of, 203; its nature, 203; the notion of, 213. Maupertuis, his Latin city, 338. Maximal and minimal problems, their rôle in physics, 14, footnote. Mayer, J. R., his conception of energy, 245, 246; his methods of thought, 247; on the conservation of energy, 163, 164, 165, 167, 183, 184; his metaphysical utterances, 183, 246; also 138, 184, 191, 217, 271, 274. Measurement, definition of, 206. Measures, international, 108. Mécanique céleste, 90, 188; sociale, and morale, the, 90. Mechanical, conception of the world, 105, 155 et seq., 188, 207; energy, W. Thomson on waste of, 175; analogies between ---- and thermal energy, 17 et seq.; equivalent of heat, electricity, etc., 164, 167 et seq.; mythology, 207; phenomena, physical events as, 182; philosophy, 188; physics, 155-160, 212; substitution-value of heat, 178, footnote. Mechanics, Kirchhoff's definition of, 236. Medicine, students of, 326. Melody, 101. Melsens, 310, 327. Memory, a treasure-house for comparison, 230; common elements impressed upon the, 180; its importance, 238; science disburdens the, 193. Mendelejeff, his periodical series, 256.