ASTROGNOSY. 31 



which Macrobius in his Somnium Scipionis, latinized by 

 Sphcera aplanes, 5 we frequently meet in Aristotle (as if he 

 wished to introduce a new technical term) with the phraso 

 rivetted stars, eVSedf/xeVa aorrpa, instead of aTrXai/^, 6 as a desig- 

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

 expressions of sidera infixa ccelo of Cicero, stellas quas 

 putamus affixas of Pliny, and astro, Jlxa 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 affixum 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, qua3 noctem decore vario distinguunt, 



5 Macrob., Somn. Scip., i. 9-10; stellce inerranfes, in Cicero 

 de nat. Deorum, iii. 20. 



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

 nical expression cVfcfc/icVa aarpa, 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 ; wnrep 

 Trpoo-TrffoKOTts. Ptolemy thus objects to the expression 

 <r(pcupa cnr\avr)s (orbis inerrans) ; " in as far as- the stars con- 

 stantly preserve their relative distances they might rightly be 

 termed dnXavels 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 d7r\avf]s 

 is inappropriate if applied to the sphere." 



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

 lius, ii. 35. 



