Equatoreal instrument, 8.
Equinox, 119.
Equinoxes, precession of, 175, 199; caused principally by moon, 181, 201.
F.
Fluid, equilibrium of, 244.
Focus of ellipse, 101.
Force, meaning of, 128.
Forces, composition and resolution of, 108, 133.
Foucault, his pendulum experiment, 277; his gyroscope, 282.
G.
Great circle, 75, 89.
Gravity, how measured, 247.
Gravitation, law of, 130, 175, 199; evidence of theory of, 217.
Gyroscope, 282.
H.
Heavens, apparent motion of, 5.
Heliometer, 214.
Hipparchus discovers precession, 202.
Horizontal point, how found, 31.
I.
Inequality of long period, 233.
J.
Jupiter, figure of, 70; satellites eclipsed, 206; attraction of by the sun, 223.
K.
Kepler's laws, 101, 126, 226; inferences from, 130.
L.
La Place explains inequalities of long period, 233.
Laws of motion, 103, 218.
Lens, 18.
Light, aberration of, 188-204; velocity of, 206; reflection of, 31, 42 , refraction of, 13, 45.
Longitude, how found, 64, 85.
Lunar nutation, 203.
M.
Mars, parallax of, 149, 168.
Mass of planet, found—from motion of satellites, 268; from perturbations, 268; of moon, 269; of earth, 265; of sun, 266.
Measurement of earth's surface, 46.
Meridian, 23.
Microscopes of mural circle, 30.
Moon, its distance, 136, 166; its parallax, 142; its orbit, 143; illumination of by sun, 148, 167; attraction of by earth, 220; its variation, 230.
Motion, apparent, of heavens. 5; of sun, 73, 88; of planets, 91; laws of, 103, 218; of stars, 215; of solar system, 216.
Mural circle, 29, 42.