xxxvm NOTES. 



olar distance, the planet Uranus will be 19 feet, and a Lyrse 138 geographical 

 miles from the Sun. 



C 07 ) p. 138. Bessel, in Schum. Jahrb. 1839, S. 53. 



( 108 ) p. 138. Mauler, Astr. S. 476. The same author, in Schum. Jahr. 

 1839, S. 95. 



( 1W ) p. 140. Sir William Herschel, Phil. Trans. 1817, Pt. 2, p. 328. 



O p. 140. Arago, Annuaire, 1842, p. 459. 



( m ) p. 141. Sir John Herschel, in a letter from Feldhauscn, Jan. 13, 

 1836. Nicholl, Archit. of the Heavens, 1838, p. 22. See also some scat- 

 tered notices by Sir William Herschel, on the starless space which separates 

 us from the Milky Way, in the Phil. Trans, for 1817, Pt. 2, p. 328. 



( 112 ) p. 141. Sir John Herschel, Astron. 624. The same author, in Obser- 

 vations of Nebute and Clusters of Stars (Phil. Trans. 1833, Pt. 2, p. 479, 



25) : " we have here a brother system, bearing a real physical resemblance 

 and strong analogy of structure to our own." 



( 113 ) p. 141. Sir Wm. Herschel, in the Phil. Trans, for 1785, Pt. 1, p. 257. 

 Sir John Herschel, Astron. 616; and in a letter, addressed to myself, in 

 March 1823, he says : " The nebulous region of the heavens forms a nebulous 

 milky way, composed of distinct nebulae as the other of stars." 



( IM ) p. 142.- Sir John Herschel, Astron. 585. 



( U4 ) p. 142, Arago. Annuaire, 1842, pp. 282285, 409411, and 

 439442. 



( l16 ) p. 142. Olbers on the Transparency of Celestial Spaces, in Bode's 

 Jahrbuch, 1826, S. 110121. 



("") p. 143. "An opening in the heavens," William Herschel, in the 

 Phd Trans, for 1785, Vol. Ixxv. Pt. 1, p. 256. Le Francois Lalande, in the 

 Connaiss. des Terns pour 1'An Vlll. p 383. Arago, Annuaire, 1842, p. 425. 



0") p. 143. Anstot. Meteor ii. 5, 1. Stneta, .NaUir. Quast. i. 14, 2. 

 "Coelum discessisse," m Cic. de Divin, i. 43. 



(" 9 ) p. 143. Aragc, Annuaire, 1842, p. 429. 



( 12 ) p. 144. In December 1837, Sir John Herschel saw the star 77 Argus, 

 tv Inch, till that time, had always appeared of the second magnitude and inva- 

 riable, increase rapidly in brightness until it became of the first magnitude. 

 Jn January 1838, its brightness was already equal to that of a Centauri. Jn 

 March 1843, it appeared to Maclear as bright as Canopns; and "even 

 Cruets looked faint by the side of TJ Argus.' 



( I21 ) p. 144. " Hence it follows, that the rays of the light of the remotest 

 nebula must have been almost two millions of years on their way, and that 



