598 COSMOS. 



its at least apparent "heterogeneity. Exciting motion in im- 

 measurably minute spaces, this heterogeneity of matter com- 

 plicates all the problems of terrestrial phenomena. 



The astronomical problems are of a simpler nature. Hitherto 

 unencumbered by the above-mentioned complications, directed 

 to the consideration of the quantities of ponderable matter 

 (masses], to the oscillations producing light and heat the 

 mechanics of the heavens has, precisely on account of this 

 simplicity, in which everything is reduced to motion, remained 

 in all its branches amenable to mathematical treatment. 

 This advantage gives to the elementary works on theoretical 

 astronomy a great and entirely peculiar charm. In them is 

 reflected what the intellectual labours of later centuries have 

 achieved by the analytical methods ; how configuration and 

 orbits are determined ; how in the phenomena of planetary 

 motion only small oscillations about a mean condition of 

 equilibrium can take place ; how the planetary system, from 

 its internal arrangement, works its preservation and perma- 

 nence by the compensation of perturbations. 



The examination of the means of forming a general con- 

 ception of the universe, the explanation of the complicated 

 celestial phenomena, do not belong to the plan of this work. 

 The physical description of the universe relates to what fills 

 space, and organically animates it, in both spheres of urano- 

 logical and telluric relations. It adheres to the consideration 

 of the discovered laws of nature, and treats of them as ac 

 quired facts, as immediate results of empirical induction. In 

 order to carry out the work of the Cosmos within the appro- 

 priate limits, and not with too great extension, it must not be 

 attempted to establish theoretically the connection of pheno- 

 mena. In this limitation of the plan laid down beforehand, I 

 have, in the astronomical volume of Cosmos, applied so much 

 the more care to the individual facts and their arrangement. 

 JTOIU the consideration, of universal space, its temperature, 



