122] The Satellites of Jupiter 153 



Mercury could revolve round an apparently moving body, 

 the sun, could not but have their doubts shaken when 

 shewn the new satellites evidently performing a motion 

 of just this character ; and most important consequence 

 of all the very real mechanical difficulty involved in the 

 Coppernican conception of the moon revolving round the 

 moving earth and not dropping behind was at any rate 

 shewn not to be insuperable, as Jupiter's satellites succeeded 

 in performing a precisely similar feat. 



The same reasons which rendered Galilei's telescopic 

 discoveries of scientific importance made them also objec- 

 tionable to the supporters of the old views, and they were 

 accordingly attacked in a number of pamphlets, some of 

 which are still extant and possess a certain amount of 

 interest. One Martin Horky, for example, a young German 

 who had studied under Kepler, published a pamphlet in 

 which, after proving to his own satisfaction that the satel- 

 lites of Jupiter did not exist, he discussed at some length 

 what they were, what they were like, and why they existed. 

 Another writer gravely argued that because the human 

 body had seven openings in it the eyes, ears, nostrils, and 

 mouth therefore by analogy there must be seven planets 

 (the sun and moon being included) and no more. How- 

 ever, confirmation by other observers was soon obtained 

 and the pendulum even began to swing in the opposite 

 direction, a number of new satellites of Jupiter being 

 announced by various observers. None of these, however, 

 turned out to be genuine, and Galilei's four remained the 

 only known satellites of Jupiter till a few years ago 

 (chapter xin., 295). 



122. The reputation acquired oy Galilei by the publica- 

 tion of the Messenger enabled him to bring to a satisfactory 

 issue negotiations \\hich he had for some time been carrying 

 on with the Tuscan court. Though he had been well 

 treated by the Venetians, he had begun to feel the burden 

 of regular teaching somewhat irksome, and was anxious to 

 devote more time to research and to writing. A republic 

 could hardly be expected to provide him with such a 

 sinecure as he wanted, and he accordingly accepted in the 

 summer of 1610 an appointment as professor at Pisa, and 

 also as " First Philosopher and Mathematician " to the Grand 



