268 COSMOS. 



annuli of the Milky Way, is extremely prejudicial to tli, 

 profound mathematical treatment of problems so difficult of 

 solution. The contemplation of our own planetary sphere, 

 whence we ascend, from the small partial systems of the moons 

 of Jupiter, Saturn, and Uranus, to the higher and general solar 

 system, has naturally led to the belief, that the fixed stars 

 might in a similar manner be divided into several indivi- 

 dual groups, and separated by immense intervals of space, 

 which again (in a higher relation of these systems one to 

 another) may be subject to the overwhelming attractive 

 force of a great central body, (one sole sun of the whole 

 universe). 34 The inference here advanced and founded 

 on the analogy of our own solar system, is, however, re- 

 futed by the facts hitherto observed, In the multiple stars 

 two or more self-luminous stars (suns) revolve, not round 

 one another, but round an external and distant centre of 

 gravity. No doubt something similar takes place in our own 

 planetary system, inasmuch as the planets do not properly 

 move round the centre of the solar body, but around the com- 

 mon centre of gravity of all the masses in the system. But 

 this common centre of gravity falls, according to the rela 

 tive positions of the great planets Jupiter and Saturn, some 

 times within the circumference of the sun's body, but oftener 

 out of it. 35 The centre of gravity, which in the case of the 

 double stars is a void, is accordingly in the solar system at 

 one time void, at another occupied by matter. All that has 

 been advanced with regard to the existence of a dark 

 central body in the centre of gravity of double stars, or at 

 least of one originally dark, but faintly illuminated by the 



84 The value or worthlessness of such views has been 

 discussed by Argelander in his essay, " Ueber die eigene 

 Bewegung der Sonnensy stems, hergeleitet aus der eigenen 

 Bewegung der Sterne, 1837, s. 39. 



96 See Cosmos, vol. i. p. 135. (Bonn's ed.) (Madler, Astr., 

 p. 400.) 



