NOTES. 



phical miles ; being 80000 English geographical miles less than the distance of 

 the Moon from the Earth. Tbe aphelion of the comet is 853'3 distances of 

 the Earth froin the Sun, and the ratio of its least to its greatest distance 

 from the Sun is as 1 : 140000. 



C 559 ) p. 401. Arago, in the Annuaire pour 1832, p. 236255. 



( 66 ) p. 402. Sir John Herschel, Outlines, 592. 



(66i) p. 402. Bernhard von Lindenau, in Schum. Astr. Nachr. No. 698, 

 S. 25. 



t 662 ) p. 402. Kosmos, Bd. iii. S. 4649 ; Engl. ed. p. 3639. 



C 663 ) p. 403. Le Verrier, in the Comptes rendus, t. xix. 1844, p. 982 993. 



( 664 j p. 404. Newton assumed that the brightest comets possess only a 

 light reflected from the Sun. Splendent cometae luce Solis a se reflexa. 

 (Princ. mathem. ed. Le Seur et Jacquier, 1760, T. iii. p. 577.) 



( 665 ) p. 404. Bessell, in Schumacher's Jahrbuch fiir 1837, S. 169. 



( 66C ) p. 404, Kosmos, Bd. i. S. 113, and Bd. iii. S. 50 ; Engl. ed. Vol. i. 

 p. 99, and Vol. iii. p. 40. 



(66? ) p. 405. Valz, Essai sur la Determination de la Densite de 1'Etner dans 

 1'Espace planetaire, 1830, p. 2 ; and Kosmos, Bd. i. S. 112 ; Engl. ed. Vol. i. 

 p. 98. Hevelius, who was always so careful and unprejudiced an observer, 

 had already had his attention drawn to the enlargement of the nuclei of 

 comets with increasing distance from the Sun (Pingre, Cometographie, T. ii. 

 p. 193). Determinations of the diameter of Eacke's comet when near the 

 Sun are very difficult, if exactness is aimed at. The comet is a nebulous mass, 

 in which the middle, or a part of the middle, is strikingly the brightest. From 

 this place, which has not at all the appearance of a disk, aud cannot be called 

 a cornet's head, the light decreases rapidly on all sides. At the same time the 

 nebulosity is prolonged in one direction, so that this prolongation appears like 

 a tail. Measureiiu'ii's of the comet's dimensions refer, therefore, to this 

 nebulosity, the circumference of which, without having any very well-defined 

 outline, diminishes when the comet is at its perihelion. 



( G68 ) p. 405. Sir John Herschel, Results of Astron. Observ. at the Cape 

 of Good Hope, 1847, 366, PI. xv. aud xvi. 



( 669 ) p. 406. Although still later (5th of March) the distance between 

 the two comets was seen to increase to 9 19', yet this increase, as Planta- 

 rnour has shewn, was only apparent, being dependent on increased approxi- 

 mation to the Earth. From February to the 10th of March, the two por- 

 tions of the double comet continued to be at an equal distance from each other. 



''' 7 ) p. 406. Le 19 fevrier 1846, on apei^oit le fond noir du ciel qui 



