252 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1908. 



fact that polar and nonioolar forces always act simultaneously in the 

 production of chemical combinations is the jDrincipal reason why in- 

 vestigators have not yet been able to fathom the nature and the law 

 of chemical forces, and is responsible for the fact that the investiga- 

 tions have not yet gotten away from a consideration of the balance 

 of energy. 



There is no need of entering here into that mooted question which 

 has been brought up many times in physical chemistry, the question 

 of the supremacy of the thermodynamic or the atomistic theory. 

 This is perhaps nearly as important as determining whether Schiller 

 or Goethe was the greater man, and should be answered in a like 

 manner: We should rejoice in the possession of tw^o resources so 

 powerful and at the present time so indispensable for scientific 

 thought. The chronicler should, however, make note of the fact that 

 most of the modern results in the domain of phj^sical chemistry have 

 been obtained by a happy combination of thermodynamic methods 

 with molecular theories, such as the creators of the modern theory of 

 heat have followed in devoting most of their work to the development 

 of the atomistic side, particularly of the kinetic theory- 

 Thermodynamics had its origin in the methods of mathematical 

 physics. The atomic theory, on the contrary, owes its high state of 

 perfection especially to chemical research. We should regard as a 

 result of the latter the application of the atomic theory to the science 

 of electricity which has begun to develop a chemical theory of elec- 

 tricity. There are many reasons for believing that the two forms of 

 electricity are composed of almost infinitely small particles, each 

 identical with the other, called " electrons." Consequently, free ions 

 should be interpreted as combinations between the elements or radicles 

 and the electrons, to which the laws of constant and multiple propor- 

 tions apply and which likewise are governed by the theory of valence. 

 We must limit, however, this brief indication of how the atomic 

 theory by such a marvelous enlargement of its horizon, has put a 

 number of physical and chemical processes in an entirely new light, 

 and end with a few words on the radio-active emanations Avhose 

 existence is made clear to us through the electron theory. 



The effects of this radiation, according to the prevailing theory, 

 are caused by the projection of electrons either in a free state or 

 bound up with matter, and whose existence is most easily determined 

 by the electroscope. These very recent researches have opened to us 

 the new world of radio-active substances. For sensitiveness this 

 method of research is often superior even to spectral analysis. As an 

 example I may mention the fact that according to the calculations of 

 a young investigator in this field, if a milligram of radium C were 

 divided among all the people living on the earth (about two thousand 

 millions) each one of them would possess an amount sufficient to dis- 



