88 COSMOS. 



more fully upon the grounds on which explanations of this 

 lubject have been based ; but observations so remarkable,* 

 and views of so exalted a character, regarding the most won- 

 derful class of the cosmical bodies belonging to our solar system, 

 ought not to be entirely passed over in this sketch of a general 

 picture of nature. 



Although as a rule the tails of comets increase in magnitude 

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

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

 remarkable example of two tails, one of which was turned 

 towards 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 

 occasioned a double, unchecked, continuous emanation of 

 nebulous matter.f 



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, 

 regarded by the Stagirite as a large comet, the substance of 

 which was incessantly being renewed. J 



* Bessel, in Schumacher, Ast. Nadir., 1836, Nr. 300-302, s. 188, 

 192, 197, 200, 202, 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). Dunlop, at 

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



f Bessel, in Ast. Nadir. 1836, No. 302, s. 231. Schum., Jahrb. 

 1837, s. 175. See also Lehriann, Ueber Cometenschweife (On the Tails 

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



J Aristot. Meteor., i. 8, 11-14, und 19-21 (ed. Ideler, t. i., pp. 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 ot 

 the elder Pythagoreans, which inculcated ideas so nearly approximating 

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

 comets are transitory meteors belonging to our atmosphere, in the ver> 

 book in which he cites the opinion of the Pythagorean school, according 

 to which these cosmical bodies are supposed to be planets, having leug 



