ASTROGSOSY. 31 



vrhich Macrobius in his Somnium Scipionis, latinized by 

 Sphara aplanes* we frequently meet in Aristotle (as if he 

 wished to introduce a new technical term) with the phrase 

 rivetted stars, e'vdfde/ueVu aorpa, instead of aTrXa^, 6 as a desig- 

 nation for fixed stars. From this form of speech arose the 

 expressions of sidera mfixa ccelo of Cicero, stellas quas 

 putamus ajfixas of Pliny, arid astro, fixa of Manilius, which 

 corresponds with our term fixed stars. 7 This idea of fixity 

 leads to the secondary idea of immobility, of persistence in 

 one spot, and thus the original signification of the expressions 

 infixum or ajfixum sidus, was gradually lost sight of in the 

 Latin translations of the middle ages, and the idea of im- 

 mobility alone retained. This is already apparent in a highly 

 rhetorical passage of Seneca, regarding the possibility of dis- 

 covering new planets, in which he says (Nat. Qucest., vii. 24) : 

 " Credis autem in hoc maximo et pulcherrimo corpore inter 

 innumerabiles stellas, quee noctem decore vario distinguunt, 



* Macrob., Somn. Scip., i. 910; stellce inerr antes, in Cicero 

 de nat. Deorum, iii. 20. 



8 The principal passage in which we meet with the tech- 

 nical expression eVSefie/ue'i/a atrrpa, is in Aristot. de Ccelo, ii. 8, 

 p. 289. 1. 34. p. 290, 1. 19, Bekker. This altered nomenclature 

 forcibly attracted my attention in my investigations into the 

 optics of Ptolemy, and his experiments on refraction. Pro- 

 fessor Franz, to whose philological acquirements I am indebted 

 for frequent aid, reminds me that Ptolemy (Syntax, vii. 1,) 

 speaks of the fixed stars as affixed or rivetted ; axmep 

 rrpoo-Trc^vKOTfs. Ptolemy thus objects to the expression 

 o-tpalpa aTrXavf/s (orbis inerrans) ; " in as far as the stars con 

 stantly preserve their relative distances they might rightly be 

 termed dirXave'is ; but in as far as the sphere in which they 

 complete their course, and in which they seem to have grown, 

 as it were, has an independent motion, the designation dirXavfjs 

 is inappropriate if applied to the sphere." 



7 Cicero, tie nat Deorum, i. 13; Plin. ii. 6 and 24; Mani- 

 lius, ii. 35. 



