XIV NOTES. 



of revolution of Encke's comet, which has already manifested itself with such 

 great regularity for sixty-three years, cannot well be conceived to be depen- 

 dent on a sum of accidental effluxes. Compare, respecting this cosmically 

 important subject, Bessel, in Schumacher's Astr. Nachr. No. 289, S. 6, and 

 No. 310, S. 345350, with Encke's Memoir on the Hypothesis of a 

 Resisting Medium, in Schum. No. 305, S. 265274. 



(**) p. 41. Olbcrs, in Schum. Astr. Nachr. No. 268, S. 58. 



(*) p. 41. Outlines of Astronomy, 556 and 597. 



( 86 ) p. 41. " En assimilant la matiere tres rare qui remplit les espaces 

 celestes quant a ses proprietes refringentes aux gas terrestres, la densite de cette 

 matiere ne saurait depasser une certaine limite doiit les observations des 

 etoiles changeantes, p. e. celles d' Algol ou de de Persee, peuvent assignor 

 la valeur (Arago, Annuaire pour 1842, p. 336 345). 



( 8 p. 41. Wollaston, in the Phil. Trans, for 1822, p. 89 ; Sir John 

 Herschel, Outl. of Astr. 34 and 36. 



t 88 ) p. 42. Newton, Princ. mathem. T. iii. (1760), p. 671 : " Vapores, 

 qai ex sole et stellis fixis et caudis cometarum oriuntur, incidere possunt in 

 atmospheeras planetarum." 



( 89 ) p. 42. Kosmos, Bd. i. S. 129 and 141 (English edition, Vol. i. p. 114 

 and 126). 



(*") p. 43. Kosmos, Bd. ii. S. 355373 and 507515 (English edition, 

 Vol. ii. p. 314330, Note 482503). 



( 91 ) p. 43. Delambre, Hist, de 1'Astronomie moderne, T. ii. p. 255, 269, 

 and 272. Morin says himself, in his Scientia Longitudinum, published in 

 1634 "Applicatio tubi optici ad alhidadam pro stellis fixis prompte et 

 accurate mensurandis a me excogitata est." Picard used no telescope with his 

 mural quadrant up to 1667 ; and Hevelius, when Halley visited him in 1679, 

 at Dantzic, and admired the exactness of his measurements of altitude (Baily, 

 Catal. of Stars, p. 38), observed through improved apertures for unassisted 

 vision. 



(92) p. 44. The unfortunate Gascoigue, whose merits were long unac- 

 knowledged, met his death, when hardly 23 years of age, at the battle of 

 Marston Moor, between Cromwell and the King's troops (see Derham, in the 

 Phil. Trans. Vol. xxx. for 17171719, p. 603610). To him belong 

 inventions or adaptations which were long attributed to Picard and Anzout, 

 and which gave to " Observing Astronomy," which has for its chief object 



