154 A Short History of Astronomy fCn. vi. 



Duke of Tuscany, with a handsome salary and no definite 

 duties attached to either office. 



123. Shortly before leaving Padua he turned his telescope 

 on to Saturn, and observed that the planet appeared to 

 consist of three parts, as shewn in the first drawing of 

 fig. 67 (chapter vm., 154). On subsequent occasions, 

 however, he failed to see more than the central body, and 

 the appearances of Saturn continued to present perplexing 

 variations, till the mystery was solved by Huygens in 1655 

 (chapter viu., 154). 



The first discovery made at Florence (October 1610) was 

 that Venus, which to the naked eye appears to vary very 

 much in brilliancy but not in shape, was in reality at times 

 crescent-shaped like the new moon and passed through 

 phases similar to some of those of the moon. This shewed 

 that Venus was, like the moon, a dark body in itself, deriv- 

 ing its light from the sun ; so that its similarity to the earth 

 was thereby made more evident. 



124. The discovery of dark spots on the sun completed 

 this series of telescopic discoveries. According to his own 

 statement Galilei first saw them towards the end of 1610,* 

 but apparently paid no particular attention to them at the 

 time ; and, although he shewed them as a matter of 

 curiosity to various friends, he made no formal announce- 

 ment of the discovery, till May 1612, by which time the 

 same discovery had been made independently by Harriot 

 ( 118) in England, by John Fabricius (1587-? 1615) in 

 Holland, and by the Jesuit Christopher Scheiner (1575-1650) 

 in Germany, and had been published by Fabricius (June 

 1611). As a matter of fact dark spots had been seen with 

 the naked eye long before, but had been generally supposed 

 to be caused by the passage of Mercury in front of the sun. 

 The presence on the sun of such blemishes as black spots, 

 the " mutability " involved in their changes in form and 

 position, and their formation and subsequent disappearance, 

 were all distasteful to the supporters of the old views, 



* In a letter of May 4th, 1612, he says that he has seen them for 

 eighteen months; in the Dialogue on the Two Systems (III., p. 312, 

 in Salusbury's translation) he says that he saw them while he still 

 lectured at Padua, i.e. presumably by September 1610, as he moved 

 to Florence in that month. 



