COMETS. 187 



light, ai^d color of comets, the emanations from their heads 

 which, bent backward,^ form the tails, from the observations 

 of Hensius (1744), Bessel, Struve, and Sir John Herschel. 

 Besides the magnificent Gsmet of 1843,t which could be 

 seen by Bowring, in Chihuahua (N."W. America), as a small 

 white cloud from nine o'clock in the morning until sunset, 

 and by Amici, in Parma, at full noon, 1° 23' eastward of 

 ihe Sun,$ the first comet of the year 1847, discovered by 



* This iformation of ike tail at the anterior part of the comet's head, 

 which has occupied Bessel's attention so much, was the opinion of New- 

 ton and Winthrop (compare Newton's Principia, p. 511, and Philos. 

 Transact., vol. Ivii., for the year 1767, p. 140, tig. 5). Newton consid- 

 ei-ed that the tail was developed most considerably and longer near the 

 Sun, because the cosmical ether (which we call, with Encke, the resist- 

 ing medium) was the densest tliere, and the particulce caudce, strongly 

 heated and supported by the ether, ascended more easily. Winthrop 

 considered that the principal effect did not take place until some time 

 after the perihelion passage, because, according to the law established 

 by Newton (Principia, p. 424 and 466), the maxima are universally re- 

 tarded (in periodical changes of heat as well as in ocean tides). 



t Arago, in the Annuaire for 1844, p. 395. The observation was made 

 by the younger Amici. 



X With regard to the Comet of 1843, which appeared with unexam- 

 pled splendor in Northern Europe during the month of March, near 

 Orion, and approached nearer- to the Sun than any hitherto observed 

 and calculated comet, all the details are collected in Sir John Herschel's 

 Outlines of Astronomy, $ 589-597 ; and in Peirce, American Almanac 

 for 1844, p. 42. On account of physiognomical resemblances whose 

 uncertainty was already shown by Seneca {Nat. Quecst., lib. ii., caps, 

 xi. andxvii.), it was at first considered to be identical with the comets 

 of 1668 and 1689 {Cosmos, vol. i., p. 139, note; Galle, in Olbers's Come- 

 tenbahnen, Nos. 42 and 50). Boguslawski (Schum., Astr. Nachr., No. 

 545, p. 272) believes on tlie contrary, that its previous appearances were 

 with a revolution of 147 years, those of 1695, 1548, and 1401 ; he even 

 calls it the Comet of Aristotle, " because he traces it back to the year 

 371 before our era, and, together with the talented Hellenist Thiersch, 

 of Munich, considers it to be a comet which is mentioned in the Mete- 

 orologicis of Aristotle, book i., cap. vi." But I'would call to mind that 

 the name Comet of Aristotle is vague and indefinite. If that one is 

 meant which Aristotle states to have disappeared in Orion, and which 

 ne connects with the earthquake in Achaia, it must not be forgotten 

 that this comet is stated by Callisthenes to have appeared before, by 

 Diodorus after, and by Aristotle at the time of the earthquake. The 

 «ixth and eighth chapters of the Meteorology treat of four comets whose 

 epochs of appearance are characterized by the archons at Athens, and 

 by unfortunate events. In this place those are mentioned in order: 

 the western comet which appeared on the occasion of the great earth- 

 quake at Achaia, accompanied with floods (cap. vii., 8) ; then the comet 

 which appeared during the time of the Archon Eucles, the son of Mo- 

 Ion ; afterward (cap. vi., 10) the Stagirite comes again to the western 

 comet, that of the great earthquake, and at the same time calls the Ar 

 chon Asteus — a name which incoiTect readings have changed into Aria 



