86 HISTORY OF MECHANICS. 



John Bernoulli took up the subject after the death 

 of his brother James, which happened in 1705. 

 The former published in 1714 his Meditatio de 

 naturd Centri Oscillationis. In this memoir, he 

 assumes, as his brother had done, that the effects 

 of forces on a lever in motion are distributed ac- 

 cording to the common rules of the lever 12 . The 

 principal generalization which he introduced was, 

 that he considered gravity as a force soliciting to 

 motion, which might have different intensities in 

 different bodies. At the same time, Brook Taylor 

 in England solved the problem, upon the same 

 principles as Bernoulli; and the question of priority 

 on this subject was one point in the angry inter- 

 course which, about this time, became common 

 between the English mathematicians and those of 

 the continent. Hermann also, in his Phoronomia, 

 published in 1716, gave a proof which, as he 

 informs us, he had devised before he saw John Ber- 

 noulli's. This proof is founded on the statical equi- 

 valence of the "solicitations of gravity" and the 

 "vicarious solicitations" which correspond to the 

 actual motion of each part ; or, as it has been ex- 

 pressed by more modern writers, the equilibrium 

 of the impressed and effective forces. 



It was shown by John Bernoulli and Hermann, 

 and was indeed easily proved, that the proposition 

 assumed by Huyghens as the foundation of his solu- 

 tion, was, in fact, a consequence of the elementary 

 12 P. 172. 



