32 COSMOS. 



juse aera minime vacuum et inertem esse patiuntur, quinque 

 solas esse, quibus exercere se liceat ; ceteras stare fixum et 

 immobilem populum?" 1 " And dost thou believe that in this 

 so great and splendid body, amongst innumerable stars, which 

 by their various beauty adorn the night, not suffering the air 

 to remain void and unprofitable, that there should be only five 

 stars to whom it is permitted to bo in motion, whilst all the 

 rest remain a fixed and immoveable multitude." Ihis fixed 

 and immoveable multitude is nowhere to be found. 



In order the better to classify the main results of actual 

 observations, and the conclusions or conjectures to which they 

 give rise, in the description of the universe, I will separate 

 the astrognostic sphere into the following sections: 



I. The considerations on the realms of space and the 

 bodies by which they appear to be filled. 



II. Natural and telescopic vision, the scintillation of the 

 stars, the velocity of light, and the photometric experiments on 

 the intensity of stellar light. 



III. The number, distribution, and colour of the stars ; 

 the stellar swarms, and the milky way which is interspersed 

 with a few nebulae. 



IV. The newly appeared and periodically changing stars, 

 and those that have disappeared. 



V. The proper motion of the fixed stars, the problematical 

 existence of dark cosmical bodies ; the parallax and measured 

 distance of some of the fixed stars. 



VI. The double stars, and the period of their revolution 

 round a common centre of gravity. 



VII. The nebulae which are interspersed in the Magel- 

 lanic clouds with numerous stellar masses, the black spot* 

 (coal-bags) in the vault of heaven. 



