THE STELLAR UNIVERSE. 



It follows therefore, that the annual motion of the sun would be 



1-623 X 95,000000 154,200000 miles; 

 and the daily motion 



a velocity equal to something more than the fourth of the earth's 

 orbital motion. 



68. The motion of the sun, which has been computed in what 

 precedes, is that which it had at a particular epoch. No account 

 is taken of the possible or probable changes of direction of such 

 motion. To suppose that the solar system should move con- 

 tinuously in one and the same direction, would be equivalent to 

 the supposition that no body or collection of bodies in the universe 

 would exercise any attraction upon it. It is obviously more 

 consistent with probability and analogy, that the motion of the 

 system is orbital, that is to say, that it revolves round some 

 remote centre of attraction, and that the direction of its motion 

 must continually change, although such change, owing to the 

 great magnitude of its orbit, and the relative slowness of its 

 motion, be so very slow as to be quite imperceptible within even 

 the longest interval over which astronomical records extend. 



Attempts have, nevertheless, been made to determine the 

 centre of the solar motion; and Dr. Madler has thrown out a 

 surmise that it lies at a point in or near the small constellation 

 of the Pleiades. 



This and like speculations must, however, be regarded as 

 conjectural for the present. 



THE FORM AND DIMENSIONS OF THE MASS OF STARS WHICH 

 COMPOSE THE VISIBLE FIRMAMENT. 



69. The aspect of the firmament might, at first, impress the 

 mind of an observer with the idea that the numerous stars scat- 

 tered over it are destitute of any law or regularity of arrange- 

 ment, and that their distribution is like the fortuitous position 

 which objects casually flung upon such a surface might be 

 imagined to assume. If, however, the different regions of the 

 heavens be more carefully examined and compared, this first 

 impression will be corrected, and it will, on the contrary, be 

 found that the distribution of the stars over the surface of the 

 celestial sphere follows a distinct and well defined law ; that 

 their density, or the number of them which is found in a given 

 space of the heavens, varies regularly, increasing continually in 

 certain directions and decreasing in others. 



Sir W. Herschel submitted the heavens, or at least that part 

 10 



