CHRONOMETER, THE (Chap. XIII.), rise and progress of time-keeping, 206-210; compensating balance, 207; detached lever escapement, 208; chronometer escapement fusee, 209 Chronometers used for determining “local time,” 281 Chronophers, for distributing “Greenwich time,” 275, 276 Cincinnati Observatory, 338 Circle, the; its first application as an astronomical instrument, 6, 7, 8, 10; division into degrees, 8, 17, 21 Circles, great, defined by Euclid, 12 CIRCLE READING (Chap. XIV.), 211-217; Digges’ diagonal scale, 213; the vernier, 214 CIRCLE, TRANSIT (_see_ Transit Circle) Circle, meridian, at Cambridge (U.S.), 248; mural, 241, 242 Circumpolar stars, 239 Clarke (Alvan), improvement in telescope lenses, 305; great equatorial at Washington, 309, 319 Clement, inventor of the anchor escapement, 197 Clepsydras, 36 CLOCK, THE (Chap. XIII.), 175-205; ancient escapement, 177; crown wheel, 178; clock train, 180; winding arrangements, 181; pendulum, 183; cycloidal pendulum, 185; compensating pendulums, 187; Graham’s, Harrison’s, and Greenwich pendulums, 188; clock at Royal Observatory, Greenwich, 194; escapements, 196; anchor escapement, 197; Graham’s dead-beat, 199; Mudge’s gravity escapement, 200; escapement of clock at Greenwich, 203; arrangements at Edinburgh Observatory, 269; astronomical, 240, 244, 245, 346; sidereal, 254, 256, 266; solar, 254; standard, at Greenwich, 194, 203, 204, 271, 274 Clock, driving, for large telescopes, 318 Clocks driven and controlled by electricity, 272 Clock stars, 267 Clock tower at Westminster, 277 Coggia’s comet, its light polarized, 450 Collimation and collimation-error in the transit instrument and equatorial, 238, 247, 328 Colour, amount produced by a lens, 81, 84, 86; spectrum analysis, 407, 408, 414, 416; of stars, 165, 351, 433; of waves of light, 420; refrangibility of, 387 Comet of 1677, discovered by Tycho Brahe, 47 Comet, measurement of the angle of position of its axis, 359 Comparison prism of the spectroscope, 423 Compensating balance, 207 Compensating pendulums, 187-193 Composite mounting of large telescopes, 310 Concave lenses (_see_ Lenses) Concave mirrors (_see_ Mirrors) Conjugate images, 64 Conjunctions of planets, first observations, 4 Constellations, first observations, 5, 9; Orion and its neighbourhood, 156 Convex lenses (_see_ Lenses) Convex mirrors (_see_ Mirrors) Cooke, adjustment of object-glasses, 141; improvement in telescope lenses, 305; equatorial refractor, 300; driving clock for large telescopes, 321; illuminating lamp for equatorial telescopes, 326 Copernicus, parallactic rules of, 41 Copernicus (lunar crater), 354 Cross wires for circle reading, 212, 216, 218; in transit eyepiece, 234, 257 Crown-glass prisms, 83, 84; lenses, 86, 88