AS'xROGNOSY. 2*7 



A.rcturus, 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 Aristi'lus and Hipparchus) that it has been ob' 

 €erved, changed its position in relation to the neighboring 

 fainter stars 2^ times the moon's diameter. Encke remarks 

 ' that the star fj, Cassiopeise appears to have moved 3i lunar 

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

 cient observations correctly indicated its position." Conclu- 

 sions based on analogy justify us in behoving that there is 

 every where progressive, and perhaps also rotatory motion. 

 The term " fixed star.s" leads to erroneous preconceptions ; 

 it may have referred, in its earliest meaning among the 

 Greeks, to the idea of the stars being riveted into the crys- 

 tal vault of heaven ; or, subsequently, in accordance with 

 the Roman interpretation, it may indicate iixity or immo- 

 bility. The one idea involuntarily led to the other. In Gre- 

 cian antiquity, in an age at least as remote as that of Anax- 

 imenes of the Ionic school, or of Alcma^on the Pythagorean, 

 all stars were divided into tcojidering [dorpa nXavcJueva or 

 7i?.avr}Td) and no?i-u'a?ideri72g fixed stars (dizXavelg darspsg 

 or dnXavTi dor pa). '^^ Besides this generally adopted desig- 

 nation of the fixed stars, which Macrobius, in his Sormiium 

 Scijnofiis, Latinized by Sjjhcsra aplanes,\ we frequently 

 meet in Aristotle (as if he wished to introduce a new tech- 

 nical term) with the phrase riveted stars, evdF.defitva dorpa, 

 instead of d~/^avTj,X as a designation for fixed stars. From 

 this form of speech arose the expressions of sidcra infixa 

 t,(Llo of Cicero, Stellas quas 'putamus afixas of Pliny, and as* 



• Pseudo-Plut., De plac. Philos., ii., 15, 16 ; Stob., Edog. Phys , p 

 082 ; Plato, in the Tlmceus, p. 40. 



t Macrob., Sonm. Scip., i., 9-10 ; siellcs. inerrantes, iu Cicero, De AuV. 

 Deorum, 'iu., 20. 



X The principal passage in wliicb we meet with the technical expres 

 fiitm kv6t6EH£va uarpa, is in Aristot., De CorJo, ii., 8, p. 289, 1. 34, p. 290, 

 1. 19, Bekker. This altered nonicnclatare forcibly attracted my atten- 

 tion in my investigations into the optics of Ptolemy, and his experi- 

 ments on refraction. Professor Franz, to w^hose philological acquire- 

 ments I am indebted for frequent aid, reminds me that Ptolemy {Syn- 

 tax, vii., 1) speaks of the fixed stai's as aSxed or riveted; uairep Trpo- 

 Grre<^VK6Teg. Ptolemy thus objects to the expression cdalpa un}.avfiQ 

 {orbis inerrans) ; " in as far as the stars constantly preserve their rela 

 live distances, they might rightly be termed dizT^avelq', but in as far as^ 

 the sphei'e in which they complete their course, and in which they seem 

 to have grown, as it were, has an independent motion, the designatioij 

 c^AQt7/f is inappi'opriate if applit-d^to the sphere." 



