SIR ISAAC XEWTON 



berent principle of movement in these minute ma- 

 terial particles would continue to act upon them, ac- 

 celerating perpetually their swiftness, until the re- 

 sistance of the ethereal medium would equal the 

 instantaneous action of the principle, when the move- 

 ment of every corpuscle would become uniform. The 

 above constituted the main features of his Corpuscular 

 Theory of light, and was compatible with the known 

 facts of the refraction of light and of the color of 

 thin plates, etc., but failed in explaining the phe- 

 nomena of the double refraction of Iceland Spar, or 

 the dispersive power of different bodies, as well as 

 many other phenomena later discovered, which have 

 led to the rejection of the corpuscular theory and the 

 universal acceptance of the vibratory theory, main- 

 tained in Newton's time by Hooke and by Huygens, 

 but rejected by Newton himself. 



The renown in which Newton's name is held is 

 especially due to the proofs he gave of the firm 

 establishment of the laws that govern the movements 

 of the solar and planetary bodies, and to the absolute 

 demonstration that they are identical with the law that 

 expresses the movement of a body dropped from 

 a heights towards the centre of the earth the law of 

 gravitation. This law is : " All bodies attract each 

 other with a force that is directly as the mass (the 

 sum of substance) and inversely as the square of the 



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