INTRODUCTION 



the facts obtained. With him began the practical 

 application of inductive reasoning. 



With SIR ISAAC NEWTON may be said to have 

 commenced nearly all that we know of Modern 

 Science. To his discoveries of the compound struc- 

 ture of a ray of light, the theory of colors and the 

 laws of gravitation, are due the facts which establish 

 the generalizations that unite our planet with the 

 whole universe. They prove that of the thousands 

 of millions of stars that exist, each is undoubtedly a 

 central sun in planetary systems of worlds somewhat 

 like our own ; which are governed by the laws that 

 govern ours, and probably have sentient beings on 

 them as wise or possibly far wiser than ourselves. 



In treating of the Interstellar Ether, whose existence 

 Newton postulated as essential to the theory of light 

 and probably that of gravitation, a disproportionate 

 space is devoted, from the desire to call attention to 

 the assured existence and probable nature of that al- 

 most incomprehensible substance : the carrier of all 

 Energy, that is within and through all matter, that 

 extends beyond the most distant Star, that brings us 

 light and life, but of which we really know almost 

 absolutely nothing. The belief in the existence of the 

 Ether, advocated by Democritus nearly 500 years B. 

 C., has of late years grown into general acceptance, 

 since it serves to explain the transmission of light, 



(xvi) 



