ISAAC NEWTON 



of his own devising for proving the same truths. 

 Profound mathematicians, among them Jean Ber- 

 noutti, combated it later. Foiitenelle, though Secre- 

 tary of the Academic des Sciences for forty-two years, 

 would only consider the laws of attraction as being 

 more than doubtful, and through his long life held 

 firmly to the Vortices of Descartes. The three 

 " Laws of Motion " given by Newton still remain 

 without change or addition. They are : 



1. That of Inertia. Every body continues in its 

 state of rest, or of uniform motion in a straight line, 

 except in so far as it may be compelled by force to 

 change that line. 



2. Change of motion is proportional to force ap- 

 plied, and takes place in the direction of the straight 

 line in which the force acts. 



3. To every action there is always an equal and 

 contrary reaction, or the mutual actions of any two 

 bodies are always equal, and oppositely directed. 



It was more than fifty years after its publication 

 that the truths demonstrated in the Principia were 

 even understood, much less embraced by the generality 

 of savants. After the completion of his great work 

 Newton confined himself to working out the details 

 of his former labors, and did not enter into any new 

 scientific work. He suffered much from sleepless- 

 ness, which was aggravated by the vexatious disputes 



"5 



