499 



LECTURE XLll. sEmT^^ 



j(lUN 





ON THE SOLAR SYSTEM. 



JL HE most conspicuous of all the celestial bodies, which we have becH 

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

 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 comparatively 

 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, there-' 

 fore, in itself highly probable that the sun may have such a motion. But 

 Dr. Herschel has confirmed this conjecture by arguments ahnost demon- 

 strative. 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 



