Argelander, magnitudes of stars, 382 Aries, its position in the zodiac, 34 Aristillus, his observations in the Alexandrian Museum, 19 _Armillæ Æquatoriæ_ of Tycho Brahe, 26, 41, 45; his _Armillæ Zodiacales_, 28 Ascension, Right (_see_ Right Ascension) Arctic circle, Euclid’s observations of stars in the, 10 Astrolabe, invented by Hipparchus, 25; engraving of Tycho Brahe’s, 26, 41; his ecliptic astrolabe, 28 Astronomical clock, 240 (_see_ Clock) ASTRONOMICAL PHYSICS (Book VI.), 371 ASTRONOMY OF PRECISION, INSTRUMENTS USED IN (Chap. XIX.), 284-290 Astrophotometer, Zöllner’s, 379 Autolycus, first map of the stars by, 8, 9 Automatic spectroscope, 397 Auzout, invention of micrometer ascribed to, 219, 221 Axis of collimation, 218, 220 B. Barium, in the sun, 419 Barlow, correction of aberration in lenses, 88; “Barlow lenses,” 89, 229 Barometrical pressure, its effect on the pendulum, 193 Berthon’s dynameter, 116 Bessel’s transit instrument, 284 Binary stars, 351, 359, 360 Blair (Dr.), object-glasses, 88 Bloxam’s improved gravity escapement, 201 Bond (Prof.), spring governor, 320, 321; celestial photography, 463 Bouguer’s photometer, 379 Brahe, Tycho (_see_ Tycho Brahe) Brewster (Sir David), his list of Tycho Brahe’s instruments, 38; spectrum analysis, 410 British Horological Institute, time signals, 280 Browning’s method of silvering glass specula, 137; of mounting specula, 144; automatic spectroscope, 397; solar spectroscope, 428 Bunsen (Ernest de), on ancient astronomical observations, 6 Bunsen (Prof.) spectroscope, 396; his burner, flame of, 407; his work in spectrum analysis, 402, 412, 423 C. Calcium, line spectra of, 406, 418 Cambridge Observatory (U.S.), equatorial at, 339; star spectroscope, 430; transit circle, 247, 248, 251 Camera, enlarging, for celestial photography, 458 Canada balsam, its power of refracting light, 447 Candles used to measure time, 176 Canopus, observations of, by Posidonius, 8 Cassegrain’s reflecting telescope, 103, 149, 169; with Mr. Grubb’s mounting, 301 Casting lenses and specula, 121 Castor, photograph of, 478 Catalogues of stars (_see_ Stars) Celestial globe, 23 CELESTIAL PHOTOGRAPHY (Chap. XXXI., XXXII.), 454 Chair, observing, for equatorial telescopes, 339 Chaldeans, their observations of the motions of the moon, 4; early use of the gnomon, 16 Chance and Feil, manufacture of glass discs, 119, 305 CHEMISTRY OF THE STARS (Chap. XXVII.-XXX.), 386-453 Chinese, observations of conjunctions of planets, 4, 5; early use of the gnomon, 16, 17 Chromatic aberration of object-glasses and eyepieces, 87, 109, 123 CHRONOGRAPH, THE (Chap. XVII.), 253-270 “Chronographic method” of transit observation, 259 Chronograph at Greenwich Observatory, 260-264