“QUADRANS MURALIS SIVE TICHONICUS.” With portrait of Tycho Brahe, instruments, etc., painted on the wall; showing assistants using the sight, watching the clock, and recording. (From the author’s copy of the _Astronomiæ Instauratæ Mechanica_.) PORTRAIT OF JOHANNES KEPLER. By F. Wanderer, from Reitlinger’s “Johannes Kepler” (Original in Strassburg). DEATH-MASK OF SIR ISAAC NEWTON. Photographed specially for this work from the original, by kind permission of the Royal Society, London. ANCIENT CHINESE INSTRUMENTS, Including quadrant, celestial globe, and two armillae, in the Observatory at Peking. Photographed in Peking by the author in 1875, and stolen by the Germans when the Embassies were relieved by the allies in 1900. SOLAR SURFACE. As Photographed at the Royal Observatory, Greenwich, showing sun spots with umbræ, penumbræ, and faculæ. SOLAR ECLIPSE, 1882. From drawing by W. H. Wesley, Secretary R.A.S.; showing the prominences, the corona, and an unknown comet. JUPITER. From a drawing by E. M. Antoniadi, showing transit of a satellite’s shadow, the belts, and the “great red spot” (_Monthly Notices_, R. A. S., vol. lix., pl. x.). COPY OF THE DRAWING MADE BY PAUL FABRICIUS. To define the path of comet 1556. After being lost for 300 years, this drawing was recovered by the prolonged efforts of Mr. Hind and Professor Littrow in 1856. SIR WILLIAM HERSCHEL, F.R.S.—1738-1822. Painted by Lemuel F. Abbott; National Portrait Gallery, Room XX. GREAT COMET, NOV. 14TH, 1882. (Exposure 2hrs. 20m.) By kind permission of Sir David Gill. From this photograph originated all stellar chart-photography. INDEX Abul Wefa, 24 Acceleration of moon’s mean motion, 60 Achromatic lens invented, 88 Adams, J. C., 61, 65, 68, 69, 70, 87, 118, 124 Airy, G. B., 13, 30, 37, 65, 69, 70, 80, 81, 114, 119 Albetegnius, 24 Alphonso, 24 Altazimuth, 81 Anaxagoras, 14, 16 Anaximander, 14 Anaximenes, 14 Anderson, T. D., 137, 138 Ångstrom, A. J., 102 Antoniadi, 113 Apian, P., 63 Apollonius, 22, 23 Arago, 111 Argelander, F. W. A., 139 Aristarchus, 18, 29 Aristillus, 17, 19 Aristotle, 16, 30, 47 Arrhenius, 146 Arzachel, 24 Asshurbanapal, 12 Asteroids, discovery of, 67, 119 Astrology, ancient and modern, 1-7, 38 Backlund, 122 Bacon, R., 86 Bailly, 8, 65 Barnard, E. E., 115, 143 Beer and Mädler, 107, 110, 111 Behaim, 74 Bessel, F.W., 65, 79, 128, 134, 139 Biela, 123 Binet, 65 Biot, 10 Bird, 79, 80 Bliss, 80 Bode, 66, 69 Bond, G. P., 99, 117, 122 Bouvard, A., 65, 68 Bradley, J., 79, 80, 81, 87, 127, 128, 139 Bredechin, 146 Bremiker, 71 Brewster, D., 52, 91, 112 Brinkley, 128 Bruno, G., 49 Burchardt, 65, 123 Burnham, S. W., 134