GALILEO 



in researches on the centre of gravity in bodies. His 

 marvelous facility in the calculations caused him to 

 be strongly recommended to John de Medici and to 

 the Grand Duke Ferdinand, who gave him the 

 Chair of Mathematics at Pisa when he was scarcely 

 twenty-five years old. He neglected nothing that 

 could serve to justify his elevation, and undertook to 

 establish the laws of motion and to ascertain the 

 solid basis of the laws of nature, not by hypothetical 

 reasoning such as had always heretofore been done in 

 all schools, but by actual experiment. He showed 

 that all bodies, whatever may be their nature, fall 

 with equal rapidity ; whenever there appears to be a 

 difference in their relative speed in falling, it is due 

 to the greater resistance of the air caused by a greater 

 extension of surface in the one body than in the 

 other. 



These new views excited the animosity of the old 

 philosophers, who tried all in their power to annoy and 

 persecute this bold innovator. They succeeded in ob- 

 liging him to leave the chair that he held at Pisa, and 

 to return to Florence without any employment. He 

 had a letter from Guido Ubaldi to a gentleman of 

 Florence of the family of Salviati, who received him 

 with great kindness and enabled him to continue his 

 discoveries until he could obtain remunerative em- 

 ployment. One of Salviati's friends, a Venetian 



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