THE FIXED STAES. 165 



of the crystalline sphere of heaven. The apparent motion 

 of all the fixed stars from east to west, while their relative dis- 

 tances remained unchanged, had given rise to this hypothesis. 

 " The fixed stars (aTrXavrj ao-rpa) belong to the higher and more 

 distant regions, in which they are rivetted, like nails, to the 

 crystalline heavens ; the planets (acrrpa 7rAai>o>/iei/a or TrXaw/ra), 

 which move in an opposite direction, belong to a lower and 

 nearer region." * As we find in Manilius, in the earliest ages 

 of the Caesars, that the term stella fixa was substituted for 

 infixa, or affixa^ it may be assumed that the schools of Rome 

 attached thereto at first only the original signification of 

 rivetted, but as the wordjixus also embraced the idea of immo- 

 bility, and might evenbe regarded as synonymous with immotus 

 amltmmobilis, we may readily conceive that the national opinion, 

 or rather usage of speech, should gradually have associated with 

 stella fixa the idea of immobility, without reference to the fixed 

 sphere to which it was attached. In this sense Seneca might 

 term the world of the fixed stars fixum et immoUlem populum. 

 Although, according to Stobaeus, and the collector 

 of the "Views of the Philosophers," the designation 

 " crystal vault of heaven" dates as far back as the early 

 period of Anaximenes, the first clearly defined signifi- 

 cation of the idea on which the term is based, occurs 

 in Empedocles. This philosopher regarded the heaven of 

 the fixed stars as a solid mass, formed from the ether which 

 had been rendered crystalline and rigid by the action of fire. 34 



33 According to Democritus and his disciple Metrodorus, 

 Stob. Eclog. phys., p. 582. 



84 Plut. deplac.phil. ii. 11 ; Diog. Laert., viii. 77; Achil- 

 es Tat. ad Arat. cap. 5, E/i7r, KpuoraAAo)?; TOVTOV (TOV ovpavbv) 

 flvai <f)T]<riv, CK TOV irayeTwdovs <ru\\e-yevTa ; in like manner we 

 only meet with the expression crystal-like in Diog. Laert., viii. 

 77, and Galenus, Hist, phil., 12, (Sturz, Empedocles Agrigent. 

 t. i. p. 321). Lactantius de opifido Dei, c. 17. "An, a. 

 mihi quispiam dixerit ceneum esse ccelum, aut vitreum, aut, 



