28 ILLINOIS ACADEMY OF SCIENCE. 



atom, which has become strongly positive, holds the oxygen of 

 the hydroxyl group firmly, but the positive hydrogen is repelled. 

 And so nitric acid ionizes and reacts as though composed of 

 hydrogen and nitrate ions. This will be clearer from an inspection 

 of the following formulas : 



+ = +— /tT4- += + + + yiP 

 H— O N<fiT H— O N r = 



The facts referred to have, of course, been long known, but as 

 far as I know, this is the first attempt at a rational explanation. 



In the development of the electron theory, the intimate connec- 

 tion between electrical phenomena and light, foreshadowed by 

 Maxwell's electromagnetic theory, more than forty years ago, 

 becomes more and more apparent. The spectrum lines are, of 

 course, to be traced back to the mo'tion of electrons, and it is not 

 an impossible dream that these lines may enable us to decipher the 

 structure of the atoms — that the atoms have a complex structure 

 no one can doubt in the light of radiochemistry. 



The color of compounds and the rotation of the plane of polar- 

 ization are also connected with the electrons. Dr. Fry, of Cincin- 

 nati, has shown how the theory may help to a solution of intricate 

 phases of the benzene problem.^ It seems very certain that it is 

 a theory with which we must reckon for some time to come. In 

 studying it we still feel keenly the need of some more fundamental 

 explanation. The elementary idea of attraction is just as difficult 

 to accept when applied to atoms bearing positive and negative 

 charges as when applied to the heavenly bodies at distances of 

 millions of millions of miles. In both cases the thoughtful mind 

 finds it impossible to believe in action at a distance without some 

 medium or mechanism to connect them. And so I can not do 

 better than to close with the words of Professor Thomson : "The 

 theory is not an ultimate one; its object is physical rather than 

 metaphysical. From the point of view of the physicist, a theory 

 of matter is a policy rather than a creed. Its object is to connect 

 or coordinate apparently diverse phenomena, and above all to 

 suggest, stimulate and direct experiment. It ought to furnish a 

 compass which, if followed, will lead the explorer further and 

 further into unexplored regions. Whether these regions will be 

 barren or fertile, experience alone will decide ; but, at any rate, 

 one who is guided in this way will travel onward in a definite 

 direction and will not wander aimlessly to and fro." 



1 Z. physik. Chem., ;6, 385, 398, 591. 



