APPENDIX IV. 



LEONARDO'S PHYSICS. 



Dr. Whewell, who seems to have studiously screened from view 

 the claims of Leonardo da Vinci to be considered as a powerful 

 exponent and advocate of experiment and induction more than a 

 century before Bacon, has to acknowledge Leonardo's greatness as a 

 scientist. 



1. " Leonardo," he says, "understood before Stevinus the oblique 

 action of pressure ; 



2. " Entertained the hypothesis of the earth's rotation ; 



3. "Gave a perfectly correct statement of the proportions of the 

 forces exerted by a cord which acts obliquely and supports a weight 

 on a lever. He distinguishes between the real levers and the 

 potential levers ; i.e., the perpendiculars drawn from the centre upon 

 the directions of the forces. Nothing can be more entirely sound 

 than this. It is quite as good as the proof of Stevinus. These 

 views must have influenced Galileo's reasonings concerning the 

 lever. 



4. " Leonardo," he goes on, " also anticipated Galileo in assert- 

 ing that the time of descent of a body down an inclined plane is to 

 the time of descent down its vertical height, in the proportion of the 

 length of the plane to the height." 



The reflection which these quotations suggest, Dr. Whewell has 

 the good grace to own, is that " both the heliocentric doctrine and 

 truths of mechanics were fomenting in the minds of intelligent men, 

 and gradually assuming clearness and strength, some time before 

 they were publicly asserted." 



And this being the case, what are we to think of Dr. WhewelFs 

 award of the palm of knowledge and influence to one who knew 



