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his time men had occupied themselves with the problem of 

 the solar system. Kepler had deducetj, from a vast mass 

 of observations, those general expressions of planetary 

 motion known as " Kepler's laws." It had been observed 

 that a magnet attracts iron; and by one of those flashes of 

 inspiration which reveal to the human mind the vast in 

 the minute, the general in the particular, it had been 

 inferred, that the force by which bodies fall to the earth 

 might also be an attraction. Newton pondered all these 

 things. He looked, as was his wont, into the darkness 

 until it became entirely luminous. How this light arises 

 we cannot explain; but, as a matter of fact, it does arise. 

 Let me remark here, that this kind of pondering is a proc- 

 ess with which the ancients could have been but imper- 

 fectly acquainted. They, for the most part, found the 

 exercise of fantasy more pleasant than careful observation, 

 and subsequent brooding over facts. Hence it is, that 

 when those whose education has been derived from the 

 ancients speak of " the reason of man," they are apt to 

 omit from their conception of reason one of its most im- 

 portant factors. Well, Newton slowly marshaled his 

 thoughts, or rather they came to him while he " intended 

 his mind/' rising like a series of intellectual births out of 

 chaos. He made this idea of attraction his own. But, to 

 apply the idea to the solar system, it was necessary to know 

 the magnitude of the attraction, and the law of its varia- 

 tion with the distance. His conceptions first of all passed 

 from- the action of the earth as a whole, to that of its con- 

 stituent particles. And persistent thought brought more 

 and more clearly out the final conclusion, that every par- 

 ticle of matter attracts every other particle with a force 

 varying inversely as the square of the distance between the 

 particles. 



Here we have the flower and outcome of Newton's in- 

 duction; and how to verify it, or to disprove it, was the 

 next question. The first step of the philosopher in this 

 direction was to prove, mathematically, that if this law of 

 attraction be the true one; if the earth be constituted of 

 particles which obey this law; then the action of a sphere 

 equal to the earth in size on a body outside of it, is the 

 same as that which would be exerted if the whole mass of 

 the sphere were contracted to a point at its center. Prac- 

 tically speaking, then, the center of the earth is the point 



