Figs. 35, 36. SPIRAL NEBULA, AS SHOWN BY THE GREAT ROSSE TELESCOPE. 



THE STELLAR UNIVERSE. 



CHAPTER Y. 



STELLAR CLUSTERS AND NEBUL.E : 76. The stars of the firmament a 

 stellar cluster. 77. Such clusters innumerable. 78. Their distribu- 

 tion on the firmament. 79. Their constitution. 80. Their apparent 

 and real forms. 81. Nebulae. 82. Double nebulae. 83. Planetary 

 nebulas. 81. Annular nebula. 85. Spiral nebulae. 



STELLAR CLUSTERS AND 



76. IT appears, then, that our sun is an individual star, forming 

 only a single unit in a cluster or mass of many millions of other 

 similar stars ; that this cluster has limited dimensions, has ascer- 

 tainable length, breadth, and thickness, and, in short, forms what 

 may be expressed by a universe of solar systems. The mind, still 

 LARDNER'S MUSEUM OP SCIENCE. 17 



2fo, 97. 



