}4 GALILEO GALILEI. 



therefore, be a devil who would impart motion to 

 the earth. 



" The planets, the sun, the fixed stars, all belong 

 to one species ; namely, that of stars they, there- 

 fore, all move, or all stand still. 



"It seems, therefore, to be a grievous wrong to 

 place the earth, which is a sink of impurity, among 

 the heavenly bodies, which are pure and divine 

 things." 



Libri, one of the Pisan professors, spoke of the 

 new discoveries as "celestial trifles." When he 

 died, Galileo naively remarked, "Libri did not 

 choose to see my celestial trifles while he was on 

 earth ; perhaps he will, now he is gone to heaven." 



Galileo now longed for freedom from teaching, 

 that he might have his time for study and writing. 

 He had planned, he said, "two books on the sys- 

 tem of the universe ; an immense work (idea, con- 

 cetto), full of philosophy, astronomy, and geometry : 

 three books on local motion, a science entirely 

 new; no one, either ancient or modern, having 

 discovered any of the marvellous accidents which 

 I demonstrate in natural and violent motions ; so 

 that I may, with very great reason, call it a new 

 science, discovered by me from its very first prin- 

 ciples : three books on mechanics, two on the 

 demonstration of its first principles, and one of 

 problems ; and though this is a subject which has 

 already been treated by various writers, yet all 

 which has been written hitherto neither in quan- 

 tity nor otherwise is the quarter of what I am 



