Undulation. A wave. Undulatory theory. The mechanical principles of the motion of waves. Vapour. Steam. Variation. A periodic inequality in the motion of the moon. Variation of the compass. The deviation of the compass needle from the true north. Vertical. The direction of the plumb-line. Vertical plane. A plane passing through the plumbline, consequently at right angles to the horizon. Vesicles. Small hollow spheres of water. Vibration. A motion to and fro. Visual ray. A ray of light coming from any object to the eye. Volta-electric induction. The disposition of electric currents to produce similar currents in bodies near them capable of receiving them. INDEX. ABERRATION of light, 31 Action, compound and dis- Algæ, 279 Algol, the star, 388 Alps, the, 273 Amazons, river of the, 117 Arago, M., 135, 219, 266, 341 133 Astronomy, physical, 1; di- Astronomical tables, 68 Attraction, its power uni- _ and repulsion, elec- -, capillary, 123, 125 diffusion, 240 Catalogue of stars by Her- Celestial bodies how seen, Centrifugal force opposed Chaldeans, observations by Chimborazo, Mount, 56 Chladni, experiment of, 147 Chronology of the visible Climate, 257, 267, 271 Cold, 264, 266 Colours, prismatic, 172 et Columbus and Lerius, 280, Comets, theory of, and de- Compass, the mariner's, 313, Eras and chronology, 100, Herschel, Miss Caroline, Fire, production of, 241 Galvanism, 300 et seq. 345 Glass, musical vibrations of, Gravity, variation in, 50 Heat, the earth's, 82; solar Sir John, 147, 195, 386, 391, 398 Italy, the north of, 56 Jupiter, the revolution of, Kater, Captain, 106 La Grange on Periodical Language, its vocal articula- La Place, 22, 37, 73, 101, Laroche's experiments in | Meridian, terrestrial, 54 optics, 229-233 Latitude, degrees of, 54 一, its velocity calcu- Lightning, 297, 304 Magnet, the, 309-339 Malus, M., optical disco- Man, frame of, 251; species Marine plants, 279 Mars, the planet, 64, 254 一, its molecular action Meridians, whether ellipti- Metals, dilation of, 243, 300 Moon, the, 34; distance of, 62 -, new, 45 -, luminous spots of and earth, reciprocal Mountains, deposits on, 86; 260 Muscular strength, 134 Nature, the laws of, 408, 413 Melloni, M., experiments, Needle, the magnetic, 310 Mercury, 327 Nautical Almanac, 47 Nebulæ; clusters of stars, Newton, 1, 21, 50, 172, et seq. -, the planet, 255, 392 Occultation of stars, 46. |