PORTION OF THE COSMOS. COMETS. 411 



of motion, which exists only in a certain class of bodies 

 belonging to the solar system, is of great importance in 

 reference to a very generally prevailing opinion respecting 

 the origin of celestial bodies belonging to one system, and 

 respecting primitive impulse. It appears to shew us the 

 comet-world, though placed in the remotest distance, sub- 

 jected to the attraction of the central body, yet possessing 

 greater individuality than the planets. Such a considera- 

 tion has led, unduly, to the idea of comets being older than 

 planets ( 677 ), of their being, as it were, primeval forms of 

 imperfectly condensed cosrnical matter in space. Under 

 this supposition it has been asked whether, notwithstanding 

 the enormous distance of the nearest fixed star of which we 

 know the parallax from the aphelion of the comet of 1680, 

 some of the comets which come within our view may not be 

 wanderers passing through our system, from the domain of 

 one sun to that of another ? 



1 propose to place next to the class of comets, as with 

 great probability belonging to the solar domain, the Ring 

 of the Zodiacal Light ; and next to that, the multitude of 

 meteoric asteroids which sometimes fall upon our Earth, 

 and respecting the existence of which as bodies in cos- 

 mical space unanimity of opinion by no means prevails. 

 As 1 myself, conformably to the examples of Chladni, 

 Gibers, Laplace, Arago, John Herschel, and Bessel, de- 

 cidedly regard aerolites as being of extra-terrestrial cos- 

 mical origin, I may naturally close the present section on 

 those cometary bodies, which have been sometimes termed 

 " wandering stars, " with the expression of a confident 

 expectation, that by increasing care and accuracy in the 

 observation of aerolites, fireballs, and falling stars, the oppo- 



