30 COSMOS. 



be considered. Innovations in the nomenclature of groups, 

 and a deviation from the meanings hitherto attached to well- 

 known names, only tend to distract and confuse the mind. 



a. ASTROGNOSY. (THE DOMAIN OF THE FIXED STARS.) 



Nothing is stationary in space. Even the fixed stars 

 move, as Halley 3 endeavoured to show in reference to Sirius, 

 Arcturus, and Aldebaran, and as in modern times has been 

 incontrovertibly proved with respect to many others. The 

 bright star Arcturus has, during the 2100 years (since the 

 times of Aristillus and Hipparchus) that it has been observed, 

 changed its position in relation to the neighbouring fainter 

 stars 2j times the moon's diameter. Encke remarks " that 

 the star //, Cassiopeise appears to have moved 3| lunar 

 diameters, and 61 Cygni about 6 lunar diameters, if the 

 ancient observations correctly indicated its position." Con- 

 clusions based on analogy justify us in believing that there 

 is everywhere progressive, and perhaps also rotatory motion. 

 The term " fixed stars " leads to erroneous preconceptions ; it 

 may have referred, in its earliest meaning among the Greeks, 

 to the idea of the stars being rivetted into the crystal vault of 

 heaven; or, subsequently, in accordance with the Roman 

 interpretation, it may indicate fixity or immobility. The 

 one idea involuntarily led to the other. In Grecian anti- 

 quity, in an age at least as remote as that of Anaximenes of 

 the Ionic school, or of Alcmeon the Pythagorean, all stars 

 were divided into wandering (ao-rpa 7rAaz/d>/io/a or TrXaj^ra) and 

 non-wandering fixed stars (an^avels aarepes or an'Xavfj mrrpa). 4 

 Besides this generally adopted designation of the fixed stars, 



8 Halley, in the Philos. Transact, for 1717, vol. xxx. 

 p. 736. 



4 Pseudo-Plut., de plac. Philos., ii. 15, 16; Stob. Eclog. 

 ., p. 582 ; Plato in the Timceus, p. 40. 



