NOTES. XXXV 



( 148 ) p. 77. Riess, in Poggen. Ann. Bd. 78, S. 433. On the non-con- 

 duction through the earth, see the important experiments of Guillemin 

 " sur le courant dans une pile isolee, et sans communication entre les poles," 

 in the Comptes rendus, T. xxix. p. 521. " Quand on remplace un fil par la 

 terre dans les telegraphes electriques, la terre sert plutot de reservoir commun 

 que de moyen d'union entre les deux extremites du fil." 



( 149 ) p. 78. Madler, Astr. S. 380. Laplace, according to Moigno, Re- 

 pertoire d'Optique moderne, 1847, T. i. p. 72: "Selon la theorie de 1'emis- 

 sion, on croit pouvoir demontrer que si le diametre d'une etoile fixe serait 

 250 fois plus grand que celui du soleil, sa densite restant la meme, 1'attraction 

 exercee a sa surface detruirait la quantite de mouvement de la molecule 

 lumineuse einise, de sorte qu'elle serait invisible a de grandes distances." 

 If, with William Herschel, we ascribe to Arcturus an apparent diameter of 

 0"'l, it would follow from this assumption that the actual diameter of 

 this star is only 11 times greater than that of our Sun (Kosrnos, Bd. i. 

 S. 153 and 415; English edition, p. 137138, and Note 107). According 

 to the above view of one of the causes of non-luminosity, it would follow that, 

 with very different dimensions of the heavenly bodies, the velocity of their light 

 would be also very different, which hitherto has by no means been confirmed 

 by observation. (Arago, in the Comptes rendus, T. viii. p. 326, says : 

 " Les experiences sur 1'egale deviation prismatique des etoiles vers lesquelles 

 la terre marche ou dont elle s'eloigne, rend compte de 1'egalite de vitesse 

 apparente des rayons de toutes les etoiles.") 



( 15 ) p. 79. Eratosthenes, Catasterismi, ed. Schaubach, 1795 ; and Era- 

 tosthenica, ed. God. Bernhardy, 1822, p. 110116. The description dis- 

 tinguishes among stars \afj.Trpovs (^yaXovs) and apavpovs (cap. 2, 11, 41). 

 So also Ptolemy : with whom ol a.u.6p<bwroi relate only to stars which are not 

 included formally in a constellation. 



( 151 ) p. 80. Ptol. Almag. ed. Halma, T. ii. p. 40 ; and in Eratosth. 

 Catast. cap. 22, p. 18 : {] Se Ke<J>aA.}; /col f) Hp-jry &vairTos oparai, 8i Se 

 vf<t>e\<a8ovs ffva-TpoQTJs So/ce? TKTIV 6pa<rQou. So also Geminus, Phsen. 

 (ed. Hilder. 1590), p. 46. 



( 152 ) p. 80. Kosmos, Bd. ii. S. 369 and 514 (Anm. 63) ; English edi- 

 tion, p. 328 and cxviii. (Note 503). 



( ls3 ) p. 80. Muhamedis Alfragani Chronologica et Astr. Elements, 1590, 

 cap. xxiv. p. 118. 



( U4 ) p. 81. Some manuscripts of the Almagest point to such sub-divisions 

 or intermediate classes, as they add to the determinations of magnitude the 



