Magnetic elements, _b._ 222. " equator, _b._ 219. Magnetism, _b._ 217. Magneto-electric induction, _b._ 256. Matter and form, _a._ 73. Mean temperature, _b._ 146. Mechanical mixture of gases, _b._ 172. Mechanico-chemical sciences, _b._ 191. Meiocene, _b._ 529. Meridian line, _a._ 164. Metals, _b._ 306, 307. Meteorology, _b._ 138. Meteors, _a._ 86. Methodic school (of medicine), _b._ 439. {36} Metonic cycle, _a._ 122. Mineral alkali, _b._ 264. Mineralogical axis, _b._ 537. Minutes, _a._ 163. Miocene, _b._ 529. Mollusca, _b._ 478. Moment of inertia, _a._ 356. Momentum, _a._ 337, 338. Moon's libration, _a._ 375. Morphology, _b._ 469, 474. Movable polarization, _b._ 105. Multiple proportions (in Chemistry), _b._ 285. Music of the spheres, _a._ 82. Mysticism, _a._ 209, 211. Nadir, _a._ **182. Nebular hypothesis, _b._ 501. Neoplatonists, _a._ 207. Neutral axes, _b._ 81. Neutralization (in Chemistry), _b._ 263. Newton's rings, _b._ 77, 124. " scale of color, _b._ 77. Nitrous air, _b._ 273. Nomenclature, _b._ 389. Nominalists, _a._ 238. Non-electrics, _b._ 194. Numbers of the Pythagoreans, _a._ 82, 216. Nutation, _a._ 465. Nycthemer, _a._ 159. Octaëteris, _a._ 121. Octants, _a._ 180. Oolite, _b._ 529. Optics, _b._ 51, &c. Organical sciences, _b._ 435. Organic molecules, _b._ 460. Organization, _b._ 435. Oscillation, Centre of, _a._ 356. Outcrop (of strata), _b._ 512. Oxide, _b._ 282. Oxyd, _b._ 282. Oxygen, _b._ 276. Palæontology, _b._ 519. Palætiological sciences, _b._ 499. Parallactic instrument, _a._ 165. Parallax, _a._ 159. Percussion, Centre of, _a._ 357. Perfectihabia, _a._ 75. Perigee, _a._ 146. Perijove, _a._ 446. Periodical colors, _b._ 93. Phases of the moon, _a._ 134. Philolaic tables, _a._ 304. Phlogisticated air, _b._ 273. Phlogiston, _b._ 268. Phthongometer, _b._ 47. Physical optics, _b._ 52. Piston, _a._ 346. Plagihedral faces, _b._ 82. Plane of maximum areas, _b._ 380. Pleiocene, _b._ 529. Plesiomorphous, _b._ 335. Plumb line, _a._ 164. Pneumatic trough, _b._ 273. Poikilite, _b._ 530. Polar decompositions, _b._ 293. Polarization, _b._ 72, 74. " Circular, _b._ 82, 119. " Elliptical, _b._ 122, 124. " Movable, _b._ 105. " Plane, _b._ 120. " of heat, _b._ 153. Poles (voltaic), _b._ 298. " of maximum cold, _b._ 146. Potential levers, _a._ 318. Power and act, _a._ 74. Precession of the equinoxes, _a._ 155. Predicables, _a._ 205. Predicaments, _a._ 206. Preludes of epochs, _a._ 46. Primary rocks, _b._ 513. Primitive rocks, _b._ 513. Primum calidum, _a._ 77. Principal plane (of a rhomb), _b._ 73. Principle of least action, _a._ 380. Prosthapheresis, _a._ 146. Provinces (of plants and animals), _b._ 562. Prutenic tables, _a._ 270. Pulses, _b._ 33. Pyrites, _b._ 352. Quadrant, _a._ 164 Quadrivium, _a._ 199. Quiddity, _a._ 234. {37} Quinary division (in Natural History), _b._ 418. Quintessence, _a._ 73.