316 EPOCHS IN THE HISTORY OP THE CONTEMPLATION OP 



essential conditions of the construction, and immediately 

 completed a telescope at Padua for his own use. ( 483 ) He di- 

 rected it first to the mountains of the moon, and shewed the 

 method of measuring their heights ; attributing, like Leo- 

 nardo da Vinci and Mostlin, the ashy coloured light of the 

 moon to the light of the sun reflected back upon her from 

 the earth. He examined with small magnifying powers the 

 group of the Pleiades, the cluster of stars in Cancer, the 

 Milky Way, and the group of stars in the head of Orion. 

 Then followed in quick succession the great discoveries of 

 the four satellites of Jupiter, the two " handles" of Sa- 

 turn, or his surrounding ring imperfectly seen so that its 

 true character was not at first recognised, the solar spots, 

 and the crescent form of Venus. 



The satellites or moons of Jupiter, (the first of all the 

 secondary planets of which the telescope disclosed the exist- 

 ence), were discovered, as it would appear, almost simulta- 

 neously, and quite independently, on the 29th of December, 

 1609, by Simon Marius, at Ansbach; and on the 7th of 

 January, 1610, by Galileo, at Padua. In the publication 

 of this discovery, Galileo, by the Nuncius Sidereus (1610), 

 preceded the Mundus Jovialis of Simon Marius (1614). ( 484 ) 

 Simon Marius wished to call Jupiter's satellites Sidera 

 Brandenburgica ; Galileo proposed Sidera Cosmica or Medi- 

 cea, of which names the last was most approved at Florence. 

 The collective name was not, however, sufficient to meet the 

 love of flattery ; and the satellites, instead of being desig- 

 nated as they are by us, by numbers, having been called by 

 Simon Marius, lo, Europa, Ganymede, and Callisto, Ga- 

 lileo substituted for these mythological personages the 



