840 HISTORY OF MECHANICS. 



CHAPTER III. 



Sequel to the Epoch of Galileo. — Period of Verification and 



Deduction. 



THE evidence on which Galileo rested the truth of the Laws of Mo- 

 tion which he asserted, was, as we have seen, the simplicity of the 

 laws themselves, and the agreement of their consequences with facts ; 

 proper allowances being made for disturbing causes. His successors 

 took up and continued the task of making repeated comparisons of the 

 theory with practice, till no doubt remained of the exactness of the 

 fundamental doctrines : they also employed themselves in simplifying, 

 as much as possible, the mode of stating these doctrines, and in tracing 

 their consequences in various problems by the aid of mathematical 

 reasoning. These employments led to the publication of various Treat- 

 ises on Falling Bodies, Inclined Planes, Pendulums, Projectiles, Spout- 

 ing Fluids, which occupied a great part of the seventeenth century. 



The authors of these treatises may be considered as the School of 

 Galileo. Several of them were, indeed, his pupils or personal friends. 

 Castelli was his disciple and astronomical assistant at Florence, and 

 afterwards his correspondent. Torricelli was at first a pupil of Cas- 

 telli, but became the inmate and amanuensis of Galileo in 1641, and 

 succeeded him in his situation at the court of Florence on his death, 

 which took place a few months afterwards. Viviani formed one of his 

 family during the three last years of his life : and surviving him and his 

 contemporaries (for Viviani lived even into the eighteenth century), 

 has a manifest pleasure and pride in calling himself the last of the 

 disciples of Galileo. Gassendi, an eminent French mathematician and 

 professor, visited him in 1628 ; and it shows us the extent of his rep- 

 utation when we find Milton referring thus to his travels in Italy :' 

 " There it was that I found and visited the famous Galileo, grown old, 

 a prisoner iu the Inquisition, for thinking in astronomy otherwise than 

 the Franciscan and Dominican licensers thouo-ht." 



Besides the above writers, we may mention, as persons who pursued 

 and illustrated Galileo's doctrines, Borelli, who was professor at Flor- 

 ence and Pisa; Mersenne, the correspondent of Descartes, win.) was 



1 Speech for the Liberty of Unlicensed Printing. 



