126 ARTHUR E. SHIPLEY 



pher and a mathematician. As the discoverer 

 of the decomposition of white hght in the spec- 

 trum, he may be regarded as the founder of 

 the modern science of optics. His discovery 

 of the law of gravitation, and his appHcation 

 of it to the explanation of Kepler's laws of 

 planetary motion and of the principal inequal- 

 ities in the orbital motion of the moon, made 

 him the founder of the science of gravitational 

 astronomy. His discovery of the method of 

 fluxions entitles him to rank with Leibnitz as 

 one of the founders of mathematical analysis. 

 All these great discoveries gave rise to long 

 and sometimes acrimonious controversies 

 among his contemporaries, relating both 

 to the subjects themselves and to priority of 

 discovery. In a letter to Halley refer- 

 ring to one of these disputes, Newton 

 writes : 



Philosophy is such an impertinently litigious lady, 



\ that a man has as good be engaged in lawsuits, as 



have to do with her. I found it so formerly, and now 



I am no sooner come near her again, but she gives me 



warning. 



His chief work, Principia, has been described 



