Fig. 56.* 



OVAL BLUISH NEBULA, OBSERVED I'.V 

 SIR JOHN HERSCHEL. 



Fig. 57.* 



THE SAME OBJECT, AS SHOWN BY THE 

 GREAT ROSSE TELESCOPE. 



THE STELLAR UNIVERSE. 



CHAPTEE IV. 



58. His discovery of binary stars. 59. Gravitation of the stars. 60. 

 Star moving round star. 61. Table of binary stars. 62. Case of 

 7"Virginis. 63. System revolving round system. PROPER MOTION OF 

 STARS : 64. The sun not a fixed centre. 65. Phenomena indicating 

 its motion. 66. Direction of the sun's motion. 67. Its velocity. 

 68. Its probable centre. THE FORM AND DIMENSIONS OF THE MASS OF 

 STARS WHICH COMPOSE THE FIRMAMENT i 69. Distribution of the stars 

 on the firmament. 70. Galactic circle and poles. 71. Variation of 

 stellar density. 72. Struve's analysis of Herschel's observations. 

 73. The milky way. 74. It consists of innumerable stars crowded 

 together. 75. Probable form of the stratum of stars in which the 

 sun is placed. 



58. SOME other explanation of the phenomena must, therefore, 

 be sought for ; and the illustrious observer soon arrived at the 

 conclusion, that these apparent changes of position were due to 

 real motions in the stars themselves ; that these stars, in fact, 

 moved in proper orbits in the same manner as the planets moved 

 around the sun. The slowness of the succession of changes which 



* See note, p. 193, vol. vii. 



LARDNER'S MUSEUM OF SCIENCE. B 1 



No. 93. 



