COMETS. 103 



I character, regarding the most wonderful class of the cosmic- 

 al bodies belonging to our solar system, ought not to be en- 

 tirely passed over in this sketch of a general picture of nature. 



Although, as a rule, the tails of comets increase in magni- 

 tude and brilliancy in the vicinity of the sun, and are directed 

 away from that central body, yet the comet of 1823 ofiered 

 the remarkable example of two tails, one of which was turned 

 toward the sun, and the other away from it, forming with 

 each other an angle of 160°. Modifications of polarity and 

 the unequal manner of its distribution, and of the direction in 

 which it is conducted, may in this rare instance have occa- 

 sioned a double, unchecked, continuous emanation of nebulous 

 matter,* 



Aristotle, in his Natural Philosophy^ makes these emana- 

 tions the means of bringing the phenomena of comets into a 

 singular connection with the existence of the Milky Way. 

 According to his views, the innumerable quantity of stars 

 which compose this starry zone give out a self-luminous, in- 

 candescent matter. The nebulous belt which separates the 

 different portions of the vault of heaven was therefore regard- 

 ed by the Stagirite as a large comet, the substance of which 

 was incessantly being renewed.! 



197, 200, 20-2, und 230. Also in Schumacher, Jahrb., 1837, s. 149, 168. 

 William Herschel, in his observations on the beautiful comet of 1811, 

 believed that he had discovered evidences of the rotation of the nucleus 

 and tail {Phil. Trans, for 1812, Part i., p. 140). Duulop, at Paramat- 

 ta, thought the same with reference to the third comet of 1825. 



* Bessel, in Astr. Nachr., 1836, No. 302, s. 231. Schum., Jahrb., 1837. 

 s. 175. See, also, Lehmaun, Ueber Cometenschiceife (On the Tails of 

 Comets), in Bode, Astron. Jahrb. fur 1826, s. 168. 



t Aristot., Meteor., i., 8, 11-14, und 19-21 (ed. Ideler, t. i., p. 32-34). 

 Biese, Phil, des Aristoteles, bd. ii., s. 86. Since Aristotle exercised so 

 great an influence throughout the whole of the Middle Ages, it is very 

 much to be regretted that he was so averse to those grander views of 

 the elder Pythagoreans, which inculcated ideas so nearly approxima- 

 ting to truth respecting the structure of the universe. He asserts that 

 comets are transitory meteors ^belonging to our atmosphere in the very 

 book in which he cites the opinion of the Pythagorean school, accord- 

 ing to which these cosmical bodies are supposed to be planets having 

 long periods of revolution. (Aristot., i., 6, 2.) This Pythagorean doc- 

 trine, which, according to the testimony of ApoUonius Myndius, was 

 still more ancient, having oingiuated with the Chaldeans, ])a3scd over 

 to the Romans, who in this instance, as was their usual practice, were 

 merely the copiers of others. The Myndian philosopher describes the 

 path of comets as directed toward the upper and remote regions of 

 heaven. Hence Seneca says, in his Nat. Qucest., vii., 17: ^^ Comeles 

 pon est species falsa, sed propHum sidus sicnt solis et lunce : altiora mnn- 

 di secat et tunc demum apparct quum in imum cwrsum stii venil;^' and 

 'Again (at vii., 27), " Cometes ceternos esse et sortis ejvsdem, cvjns ctr.tera 



