Stellar and Planetary Evolution. 7 1 



space occupied by our solar system, extending far beyond the orbit 

 of the outermost known planet, Neptune. This globe of gaseous 

 matter (assumed to be the sun and his atmosphere) was imbued 

 into a slow rotatory motion upon its own axis in process of con- 

 densation as the mass cooled down and contracted toward the 

 centre, and as its rotatory motion would increase the equatorial 

 parts would bulge outward, and a ring of gaseous matter would be 

 formed which would be cast off from the contracting central body. 

 The nucleus would continue to contract, and another and yet 

 another nebulous ring would be cast off, and these rings would 

 break up and become compacted together into separate globes, 

 which would each rotate upon its axis, and in some cases would 

 also give off rings. The primary rings cast off as above 

 mentioned would go to form the planets, and the secondary 

 rings to form their satellites. It was mentioned that, as this 

 hypothesis was formulated prior to the discovery of the great 

 principle of the conservation of energy, and before the mechani- 

 cal equivalence of heat with other forms of energy had become 

 known to scientists, it was necessary to modifj' the theory of 

 Laplace to some extent. In its main features, however, this 

 hypothesis, duly modified, may now he said to hold the field, 

 and it certainly constitutes the basis of all our speculations 

 upon the subject of planetary evolution from cosmical matter. 

 The annular, spiral, elliptical, and irregular types were concisely 

 described. The famous nebulae to be found in the constellations 

 Orion and Andromeda were specially illustrated by photo- 

 graphs, which were taken by Dr. Roberts, F.R.S., and the 

 locations in the heavens of these interesting objects were 

 pointed out by the lecturer. 



The lecturer next dealt with the past, present, and probable 

 future of the central sun of our solar system, comparing it with 

 one of the stars of the Plough, or Ursa Major (the Great Bear), 

 a beautiful star, which he said, was in its double combination 

 forty times greater in magnitude and intensity of brilliancy 

 than our own sun, which in its turn was one of the myriads 

 of stars which crowd space in gevery conceivable direction. 



