ASTROGNOSY. 31 



which. Macrobius in his Somnium Scipionis, latinized by 

 Sphcera aplanesf we frequently meet in Aristotle (as if he 

 wished to introduce a new technical term) with the phrase 

 r wetted stars, eVdeSe/ieVa aorpa, instead of dn\avr),* as a desig- 

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

 expressions of sidera infixa coelo of Cicero, stellas quas 

 putamus affixas of Pliny, and 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 

 uifixum 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, quae noctem decore vario distinguunt, 



6 Macrob., Somn. Scip., i. 9-10; stellce inerr antes, in Cicero 

 de nat. Deorum, iii. 20. 



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

 nical expression /Se8e/ieVa arrrpa, 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 ; &<nrep 

 frpoairc^vKOTfs. Ptolemy thus objects to the expression 

 o-(palpa arrXai^p (orbis inerrans) ; " in as far as the stars con 

 stantly preserve their relative distances they might rightly be 

 termed dirXavels ; 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." 



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

 lius, ii. 35. 



