| PLATE | To face page |
| I. | [The 40⁃inch Refractor of the Yerkes Observatory] | [Frontispiece] |
| II. | [Six-inch Photo-Visual Refractor, equatorially mounted] | [31] |
| III. | [Twenty-inch Reflector, Stanmore Observatory] | [36] |
| IV. | [Telescope House and 8½-inch 'With' Reflector] | [38] |
| V. | [The Sun, February 3, 1905. Royal Observatory, Greenwich] | [49] |
| VI. | [Photograph of Bridged Sunspot (Janssen). Knowledge, February, 1890] | [50] |
| VII. | [Solar Surface with Faculæ. Yerkes Observatory] | [60] |
| VIII. | [Coronal Streamers: Eclipse of 1898. From Photographs by Mrs. Maunder] | [71] |
| IX. | [The Chromosphere and Prominences, April 11, 1894.
Photographed by M. H. Deslandres] | [74] |
| X. | [Venus. H. MacEwen. Five-inch Refractor] | [94] |
| XI. | [The Moon, April 5, 1900. Paris Observatory] | [102] |
| XII. | [The Moon, November 13, 1902. Paris Observatory] | [108] |
| XIII. | [The Moon, September 12, 1903. Paris Observatory] | [110] |
| XIV. | [Region of Maginus: Overlapping Craters. Paris Observatory] | [112] |
| XV. | [Clavius, Tycho, and Mare Nubium. Yerkes Observatory] | [114] |
| XVI. | [Region of Theophilus and Altai Mountains. Yerkes Observatory] | [117] |
| XVII. | [Apennines, Alps, and Caucasus. Paris Observatory] | [119] |
| XVIII. | [Chart of the Moon. Nasmyth and Carpenter] | [125] |
| XIX. | [Key to Chart of Moon. Nasmyth and Carpenter] | [125] |
| XX. | [Mars: Drawing 1, January 30, 1899—12 hours. Drawing 2, April 22, 1903—10 hours] | [135] |
| XXI. | [Chart of Mars. Memoirs of the British Astronomical Association, Vol. XI., Part III., Plate VI.] | [139] |
| XXII. | [Jupiter, January 6, 1906—8 hours 20 minutes. Instrument, 9¼-inch Reflector] | [159] |
| XXIII. | [Jupiter, February 17, 1906. J. Baikie, 18-inch Reflector] | [167] |
| XXIV. | [Saturn, July 2, 1894. E. E. Barnard, 36-inch Equatorial] | [172] |
| XXV. | [Great Comet. Photographed May 5, 1901, with the 13-inch Astrographic Refractor of the Royal Observatory, Cape of Good Hope] | [211] |
| XXVI. | [Photographs of Swift's Comet. By Professor E. E. Barnard] | [220] |
| XXVII. | [Region of the Milky Way in Sagittarius, showing a Double Black Aperture. Photographed by Professor E. E. Barnard] | [233] |
| XXVIII. | [Irregular Star Clusters. Photographed by E. E. Barnard] | [256] |
| XXIX. | [Cluster M. 13 Herculis. Photographed by Mr. W. E. Wilson] | [259] |
| XXX. | [Photograph of the Orion Nebula (W. H. Pickering)] | [263] |
| XXXI. | [Photographs of Spiral Nebulæ. By Dr. Max Wolf] | [265] |
| XXXII. | [Photograph of Whirlpool Nebula (M. 51). Taken by Mr. W. E. Wilson, March 6, 1897] | [265] |