ON THE SOLAR SYSTEM. 397 



Obs. at Madras, 1832. Bianchi, Atti del Osserv. di Modena, fol. 1834. Richard- 

 sdn, Obs. at Paramatta, 4to, Lond. 1835. Cerquero, Obs. en San Fernando, fol. 

 S. F. 1835, Henderson, Decl. of 172 Fixed Stars observed at the Cape of Good 

 Hope, 4to, Edin. 1835. 



-To these we must add the volumes which are issued from the observatories of 



'trafnwich (Airy), Cambridge (Challis), Edinburgh (Henderson), Dorpat (Struve), 



Oxford (Johnson), Berlin (Encke), Konigsberg (Bessel), Altona (Schumacher), 



Paris (Arago), Vienna (Littrow), Palermo (Cacciatore) ; the Nautical Almanac, 



&c. &c. 



LECTURE XLII. 



ON THE SOLAR SYSTEM. 



THE most conspicuous of all the celestial bodies, which we have been 

 examining, is the sun, that magnificent luminary which occupies the centre 

 of the system that comprehends our earth, together with a variety of other 

 primary and secondary planets, and a still greater number of comets. 



The sun agrees with the fixed stars in the property of emitting light con- 

 tinually, and in retaining constantly its relative situation with very little 

 variation ; it is probable also that these bodies have many other properties 

 in common. The sun is, therefore, considered as a fixed star compara- 

 tively near us ; and the stars as suns at immense distances from us : and 

 we infer from the same analogy, that the stars are possessed of gravitation, 

 and of the other general properties of matter ; they are supposed to emit 

 heat as well as light ; and it has with reason been conjectured that they 

 serve to cherish the inhabitants of a multitude of planetary bodies revolving 

 round them. 



The sun, like many other stars, has probably a progressive motion, 

 which is supposed,* from a comparison of the apparent motions of a great 

 number of the stars, to be directed towards the constellation Hercules. 

 It is beyond all question that many of the stars have motions peculiar to 

 themselves, and it is not certain that any of them are without such motions : 

 it is, therefore, in itself highly probable that the sun may have such a 

 motion. But Dr. Herschelt has confirmed this conjecture by arguments 

 almost demonstrative. He observes that the apparent proper motions of 44 

 stars out of 56 are very nearly in the direction which would be the result 

 of such a real motion of the solar system : and that the bright stars 

 Arcturus and Sirius, which are probably the nearest to us, have, as they 

 ought to have, the greatest apparent motions. Besides, the star Castor 

 appears, when viewed with a telescope, to consist of two stars, of nearly 

 equal magnitude; and though they have both a considerable apparent 

 motion, they have never been found to change their distance a single 



* Mayer, De Motu Fixarum, Getting. 1760. Wilson, Thoughts on general Gra- 

 vitation, and Views thence arising as to the state of the Universe, 1777. Lalande, 

 Mem. del'Acad. 1776. 



f Herschel, Ph. Tr. 1783, Ixxiii. 247. 



