A HISTORY OF SCIENCE 



experiment. It remained for Galileo's Italian succes- 

 sors of the Accademia del Cimento of Florence to im- 

 prove upon the apparatus, after the experiments of 

 Torricelli to which we shall refer in a moment had 

 thrown new light on the question of atmospheric press- 

 ure. Still later the celebrated Huygens hit upon the 

 idea of using the melting and the boiling point of 

 water as fixed points in a scale of measurements, 

 which first gave definiteness to thermometric tests. 



TORRICELLI 



In the closing years of his life Galileo took into his 

 family, as his adopted disciple in science, a young man, 

 Evangelista Torricelli (1608-1647), wno proved him- 

 self, during his short lifetime, to be a worthy follower 

 of his great master. Not only worthy on account of 

 his great scientific discoveries, but grateful as well, for 

 when he had made the great discovery that the "suc- 

 tion" made by a vacuum was really nothing but air 

 pressure, and not suction at all, he regretted that so 

 important a step in science might not have been made 

 by his great teacher, Galileo, instead of by himself. 

 " This generosity of Torricelli," says Playfair, "was, per- 

 haps, rarer than his genius : there are more who might 

 have discovered the suspension of mercury in the ba- 

 rometer than who would have been willing to part with 

 the honor of the discovery to a master or a friend." 



Torricelli's discovery was made in 1643, less than 

 two years after the death of his master. Galileo had 

 observed that water will not rise in an exhausted tube, 

 such as a pump, to a height greater than thirty-three 

 feet, but he was never able to offer a satisfactory ex- 



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