CX11 NOTES. 



Kepler, who in German letters always signed his name Keppler, was not born 

 on the 21st of December, J 571, in the imperial town Weil, as is usually sup- 

 posed, but on the 27th of December, 1571, in the Wurtemberg village of 

 Magstatt. Of Copernicus it is uncertain whether he was born on the 19th 

 of January, 1472, or on the 19th February, 1473 (as Mostlin supposes), of 

 (according to Czynski) on the 12th February of the same year. The year of 

 Columbus's birth was long uncertain within 19 years. Ramusio places it in 

 1430, Bernaldez, the friend of the discoverer, in 1436, and the celebiatel 

 historian Mufloz in 1446. 



( 478 ) p. 312. Plut. de Plac. Philos. ii. 14; Aristot. Meteorol. xi. 8, De 

 Coelo, ii. 8. On theories of the spheres generally, and on the retrograding 

 spheres of Aristotle in particular, see Ideler's Vorlesung iiber Eudoxus, 1828, 

 S. 4960. 



( 479 ) p. 313. A better insight into the free movement of bodies, and into 

 the independence of the direction of the axis of the earth once given, and of 

 the rotatory and progressive movement of the terrestrial globe in its orbit, has 

 freed the original system of Copernicus from the assumption of a declination- 

 movement, or a so-called third movement of the earth (De Revolut. Orb. Ccel. 

 lib. i. cap. 11, triplex motus telluris). In the annual revolution round th 

 sun, the parallelism of the earth's axis is maintained in conformity with the 

 law of inertia, without the application of a " correcting" epicycle. 



f 480 ) p. 314. Delambre, Hist, de 1'Astronomie ancienne, T. ii. p. 381 

 ( m ) p. 314. See Sir David Brewster's judgment on Kepler's optical 

 works, in the " Martyrs of Science," 1846, p. 179182. (Compare Wilde, 

 Gesch. der Optik, 1838, Th. i. S. 182210.) If the law of the refraction 

 of rays of light belongs to the Ley den Professor Willebrord Snellius (1626), 

 who at his decease left it behind him buried in his papers, on the other hand 

 the publication of the law in a trigonometrical form was first made by Des- 

 cartes. See Brewster, in the North British Beview, Vol. vii. p. 207 ; Wilde, 

 Gesch. der Optik, Th. i. S. 227. 



C* 82 ) p. 314. Compare two excellent memoirs on the discovery of thj 

 telescope, by Professor Moll of Utrecht, in the Journal of the Royal Institu- 

 tion, 1831, Vol. i. p. 319 ; and by Wilde at Berlin, in his Gesch. der Optik, 

 1838, Th. i. S. 138172. The work of Moll, written in the Dutch lan- 

 guage, is entitled, " Geschiedkundig Onderzoek naar de eerste Uitfinders der 

 Vernkykers, uit de Aantekenningen van wyle den Hoogl. van Swinden zamen- 

 gesteld door G. Moll," Amsterdam, 1831. Olbers has given an extract from 

 this interesting treatise in Schumacher's Jahrbuch fur 1843, S. 5665. The 



