1910.] RESEARCHES IN COSMICAL EVOLUTION. 219 



under the action of the planets. The theory is now extended to 

 the asteroids and satellites, and these two classes of bodies are 

 shown to be closely related. The survival of satellites near the 

 principal planets shows that our system was once filled with these 

 small masses. Such moons naturally developed in the condensation 

 of a nebula, and all nebulse include multitudes of solid globes in 

 addition to the gaseous matter shown by the spectroscope. 



20. The collisions of satellites with the larger globes, as shown 

 by the battered surface of our moon, give rise to part of the light 

 of the nebulse, and no doubt also to some of the cosmical dust with 

 which they are filled. 



21. The whirling of a spiral nebula is due to the unsym- 

 metrical meeting of two streams of nebulosity, which thus coil up, 

 and settle down under the effects of mutual gravitation ; or to the 

 mere gravitational settling of a nebula of unsymmetrical figure. 

 The inevitable result is a whirling cosmical vortex, and eventually 

 a star surrounded by a cosmical system. 



22. Nearly all single stars have planetary system revolving 

 about them, and in the immensity of the starry heavens an infinite 

 number of the planets are habitable, and no doubt actually inhabited. 

 Life is almost as general a phenomenon in the universe as matter 

 itself, though our dominant materialistic philosophy is loth to 

 admit it. 



23. We can see only visual and spectroscopic binary stars in 

 the sidereal universe, owing to the immense distances which render 

 the smaller bodies wholly invisible in our telescopes ; but we know, 

 from the example of the solar system and from the causes which 

 have operated in its formation, that planets and satellites exist 

 everywhere about the fixed stars. 



24. In star clusters the motion is shown to be of a spiral char- 

 acter, as in the nebulse, where we can trace the streams of move- 

 ment by the nebulosity, and the same theory is applied to the milky 

 way. It is shown by calculation based on the best modern data, 

 that the extent of the sidereal universe actually exceeds the vast 

 dimensions found by Sir William Herschel, and of late years held 

 to be extreme. 



It will readily be understood that the lines of argument by 



