420 COSMOS. 



Sequence of the planetary discoveries (of principal and secon- 

 dary planets} since the invention of the telescope in the 

 year 1608. 



A. The Seventeenth Century. 



Four satellites of Jupiter: Simon Marius, at Ansbach, Decem- 

 ber 29, 1609; Galileo, January 7, 1610, at Padua. 



Triple configuration of SATURN: Galileo, November, 1610; 

 Hevelius, hypothesis of two lateral bars, 1656; Huygens, 

 final discovery of the true form of the ring, December 7, 

 1657. 



The sixth satellite of Saturn (Titan) : Huygens, March 25, 

 1655. 



The eighth satellite of Saturn (the outermost, Japetus): 

 Domin. Cassini, October, 1671. 



The fifth satellite of Saturn (Rhea) : Cassini, December 23, 

 1672. 



The third and fourth satellites of Saturn (Tethys and Dione) : 

 Cassini, end of March, 1684. 



B. The Eighteenth Century. 



URANUS: William Herschel, May 13, 1781, at Bath. 



The second and fourth satellites of Uranus : William Herschel, 



January 11, 1787. 

 The first satellite of Saturn (Mimas): William Herschel, 



August 28, 1789. 

 The second satellite of Saturn (Enceladus) : William Herschel, 



September 17, 1789. 

 The first satellite of Uranus: William Herschel, January 18, 



1790. 

 The fifth satellite of Uranus: William Herschel, February 9, 



1790, 



