NOTES. 



cxxi 



In order to supply the means of examining the accuracy of these results, I sub- 

 join once more the actual mean distances of the planets as at present recog- 

 nised, and in the same table the numbers which, two centuries and a half ago, 

 Kepler regarded as the true values according to Tycho Brahe's observations. 

 I take the latter from Newton's paper, entitled De Mundi Systemate (Opus- 

 cula math., philos. et philol. 1744, T. ii. p. 11). 



( 526 ) p. 324. The Sun, which Kepler, probably from enthusiasm for the 

 " divina inventa" of his justly celebrated contemporary William Gilbert, re- 

 garded as magnetic, and whose rotation in the same direction as the planets 

 he maintained before the solar spots had been discovered, is declared by Kepler 

 to be " the densest of all celestial bodies, because he nroves all the rest which 

 belong to his system." (Comment, de motibus Stellse Martis, cap. 23 ; and 

 in Asironomise pars optica, cap. 6.) 



( 5? ) p. 324. Newton de Mundi Systemate, in Opusculis, T. ii. p. 17 : 

 " Corpora Veneris et Mercurii majore Solis calore magis concocta et coagulata 

 snnt. Planetse ulteriores, defectu caloris, carent substantiis illis metallicis et 

 mineris ponderosis quibus Terra referta est. Densiora corpora quse Soli pro- 

 piora : ea ratione constabit optime pondera Planetarum omnium esse inter 

 se ut vires." 



( 528 ) p. 328. Madler, Astronomie, 193. 



( 529 ) p. 329. Humboldt de Distribution geographica Plantarum, p. 104 

 (AnsiVMen der Natur, Bd. i. S. 131 bis 133). 



(( 53D ) p. 330. L'eteudue entiere de cette variation serait d'environ 12 

 degres, mais 1'action du Soleil et de la Lune 1'a reduit a peu pres a trois 

 degies (centesimaux,). Laplace, Expos, du Syst. du Monde, p. 303. 



( l ) p. 330. I have shewn elsewhere by the comparison of numerous mean 

 annual temperatures, that in Europe, from the North Cape to Palermo, a dif- 



