UO COSMOS. 



to the ecliptic* On comparing the number of fixed stars m 

 the Hipparcho-Ptolemaic Catalogue, Almagest, ed. Halma, 

 t. ii., p. 83 (namely, for the first mag., 15 stars ; second, 45 ; 

 third, 208 ; fourth, 474 ; fifth, 217 ; sixth, 49), with the 

 numbers of Argelander as already given, we find, as might 

 be expected, a great paucity of stars of the fifth and sixth 

 magnitudes, and also an extraordinarily large number of 

 those belonging to the third and fourth. The vagueness in 

 the determinations of the intensity of light in ancient and 

 modern times renders direct comparisons of magnitude ex- 

 tremely uncertain. 



Although the so-called Ptolemaic catalogue of the fixed 

 stars enumerated only one fourth of those visible to the naked 

 eye at Rhodes and Alexandria, and, owing to erroneous re- 

 ductions of the precession of the equinoxes, determined their 

 positions as if they had been observed in the year 63 of our 

 era, yet, throughout the sixteen hundred years immediately 

 following this period, we have only three original catalogues 

 of stars, perfect for their time ; that of Ulugh Beg (1437), 



* Compare Delambre, Hist, de VAstr. Anc, torn, i., p. 184 ; torn, ii., 

 p. 260. The assertion that Hipparchus, in addition to the right ascen- 

 sion and declination of the stars, also indicated their positions in his 

 catalogue, according to longitude and latitude, as was done by Ptolemy, 

 is wholly devoid of probability and in direct variance with the Alma- 

 gest, book vii., cap. 4, where this reference to the ecliptic is noticed as 

 something new, by which the knowledge of the motions of the fixed 

 stars round the pole of the ecliptic may be facilitated. The table of 

 stars with the longitudes attached, which Petrus Victorius found in a 

 Medicean Codex, and published with the life of Aratus at Florence in 

 1567, is indeed ascribed by him to Hipparchus, but without any proof. 

 It appears to be a mere rescript of Ptolemy's catalogue from an old 

 manuscript of the Almagest, and does not give the latitudes. As Ptole- 

 my was imperfectly acquainted with the amount of the retrogression of 

 the equinoctial and solstitial points (Almag., vii., c. 2, p. 13, Halma), 

 and assumed it about y^ too slow, the catalogue which he determined 

 for the beginning of the reign of Antoninus (Ideler, op. cit., s. xxxiv.) 

 indicates the positions of the stars at a much earlier epoch (for the year 

 63 A.D.). (Regarding the improvements for reducing stars to the time 

 of Hipparchus, see the observations and tables as given by Encke in 

 Schumacher's Astron. Nachr., No. 608, s. 113-126.) The earlier epoch 

 to which Ptolemy unconsciously reduced the stars in his catalogue cor- 

 responds tolerably well with the period to which we may -refer the 

 Pseudo-Eratosthenian Catasterisms, which, as I have already elsewhere 

 observed, are more recent than the time of Hyginus, who lived in the 

 Augustine age, but appear to be taken from him, and have no connec- 

 tion with the poem of Hermes by the true Eratosthenes. (Eratostheni- 

 ea, ed. Bernhardy, 1822, p. 114, 116, 129.) These Pseudo-Eratosthe- 

 nian Catasterisms contain, moreover, scarcely 700 individual stars dis- 

 tributed among the mythical constellations. 



