The objective point and the rate of motion thus stated, exact science holds her peace. Here genuine knowledge stops; and we can proceed further only by the aid of that imagination which men of science need to curb at every moment. But let no one think that the sun will ever reach the so-called apex. To do so would mean cosmic motion upon a straight line, while every consideration of celestial mechanics points to motion upon a curve. When shall we turn sufficiently upon that curve to detect its bending? 'Tis a problem we must leave as a rich heritage to later generations that are to follow us. The visionary theorist's notion of a great central sun, controlling our own sun's way in space, must be dismissed as far too daring. But for such a central sun we may substitute a central centre of gravity belonging to a great system of which our sun is but an insignificant member. Then we reach a conception that has lost nothing in the grandeur of its simplicity, and is yet in accord with the probabilities of sober mechanical science. We cease to be a lonely world, and stretch out the bonds of a common relationship to yonder stars within the firmament. INDEX PAGE Airy, Astronomer Royal, 1 Allis, photographs comet, 101 Andromeda nebula, 28 temporary star, 28, 29, 45 Apex, of solar motion, explained, 221 Aquila, constellation, temporary star in, 40 Arctic regions, position of pole in, 194 Argo, constellation, variable star in, 205 Association, international geodetic, 139 Asteroids, first discovery by Piazzi, 59, 106 discovery by photography, 64 group of, 63 photography of, invented by Wolf, 104 Astronomer, royal, 1 working, description of, 152 ASTRONOMER'S POLE, THE, 184 Astronomy, journalistic, 176 practical uses of, 112 Atmospheric refraction, explained, 193 Axis, of figure of the earth, 136 of rotation of the earth, 136 polar, of telescope, 173 Barnard, discovers satellite of Jupiter, 51 Bessel, measures Pleiades, 15 Bond, discovers crape ring of Saturn, 144 Bradley, observes at Greenwich, 219 Brahe, Tycho, his temporary star, 40 Bruce, endows polar photography, 197 Campbell, observes Pole-star, 18 Cape of Good Hope, observatory, photography at, 101 telescope, 170, 174 _Capriccio_, Galileo's, 55 Cassini, shows Saturn's rings to be double, 144 Cassiopeia, temporary star in, 40 Celestial pole, 184 Central sun theory, 223 Centre of gravity, 217 Chart-room, on ship-board, 5 Chronometer, invention of, 8 Circle, meridian, explained, 189 Clerk Maxwell, discusses Saturn's rings, 146 Clock, affected by temperature, 117 affected by barometric pressure, 117 astronomical, 115 astronomical, how mounted, 116 astronomical, its dial, 116 error of, determined with transit, 118 jeweller's regulator, 114 of telescope, 175 Clusters of stars, photography of, 98