RELATIONS TO PHYSICS AND CHEMISTRY 307 



dominant generalizations to outline. The first is Mitscherlich's dis- 

 covery of the fact that analogous molecular constitution corresponds 

 to analogous outer crystalline form, to so-called isomorphism. Let me 

 add that there is hardly any more satisfactory proof of the soundness 

 of our concept of the internal structure of matter than, e. g., the 

 identity of the crystalline forms of the alums, which we consider to 

 have corresponding internal structure. 



A second step, to a certain extent a similar one, was made by Pas- 

 teur when he deduced disymmetry of molecular constitution from 

 disymmetry in behavior, optically as well as crystallographically. For 

 instance, the dextrorotatory ordinary tartaric acid and its Isevorota- 

 tory antipode showed this disymmetry both in optical rotation and 

 in the particular so-called enantiomorphous crystalline form. The 

 molecules were supposed to have analogous structures differing from 

 each other as the right hand from the left. As is well known, it was 

 only later that the probable molecular structure was sharply defined, 

 and stereochemistry was founded. 



The third great step was the opening of a way to determine the 

 molecular weights of dissolved substances. It was chiefly the appli- 

 cation of Avogadro's law to osmotic pressures, in connection with 

 Raoult's measurements of freezing-points and vapor-pressures, that 

 opened the way. We may now assert that the liquid state is not char- 

 acterized by high molecular complexity. But the great innovation, 

 introduced by Arrhenius and immediately brought into relation with 

 the achievement in question, was the admission of the existence of 

 ions in electrolytes - - for example, the presence of negatively charged 

 chlorine atoms and positively charged sodium atoms in an ordinary 

 salt solution. Once more it was a physical property, the electrical 

 conductivity, that led to this extremely fruitful supposition. 



Conclusion. If, after this short summary of its properties, we try 

 to look into the nature of matter, we conclude that matter is not con- 

 tinuous, but that there are centres of action which seem to have an 

 eternal existence, changing only in the place that they occupy - 

 these are the atoms. They keep together in some way and form the 

 molecule; how, it is pretty hard to say. The planetary constellation, 

 with ordinary attraction and centrifugal force in equilibrium, is ex- 

 cluded by the consideration that at the absolute zero there is no 

 movement at all. The repulsive force that we want might be of elec- 

 trical nature; and so we come to our combination of material and 

 electrical atoms. There is indeed something fascinating here, and 

 when we admit for carbon that it may unite to four equally charged 

 electrical atoms and hold them by a force of the nature of elasticity, 

 we have at once a possible equilibrium and the tetrahedral grouping. 

 My only difficulty is that an uncharged atom of carbon, coming into 

 contact with the ions just described, would take away half the electric 



