410 SEE— THE NEW THEORY OF EARTHQUAKES [November 15, 



geodesy, are closely connected and mutually dependent upon a 

 single physical cause, namely the secular leakage of the ocean 

 bottoms; but also that the magnetism of the earth is intimately 

 connected with the forces which modify the earth's crust, because 

 the chief seat of the permanent magnetism is shallow. Thus seven 

 great classes of natural phenomena are shown to be mutually con- 

 nected and dependent on the forces which have crumpled the 

 crust of our planet. 



11. In the paper on the temperature of the earth it was shown 

 from the mathematical theory of heat as applied to the secular 

 cooling of the globe that when the gravitational potential of the 

 mass alone is the source of energy considered, the most probable 

 age of the consolidated earth is some ten million years. Varia- 

 tions of the data there used might possibly double this age, but 

 it is doubtful if further extension of the time limit of the past 

 history of our planet is possible without invoking the aid of sub- 

 atomic energies as exemplified in radium and kindred radio-active 

 substances. At present we know too little of radium and similar 

 elements to be able to affirm with confidence that the heat resulting 

 from the transformation of these substances does not prolong the 

 life of our planet; yet as radium has no known connection with 

 volcanoes, earthquakes, and moimtain formation, but, from the 

 absence of outbreaks in the interior of continents, seems to be 

 everywhere in an essentially quiescent or dormant condition, it 

 is natural to infer that it plays only a subordinate part in cosmical 

 processes. It may, however, be of great importance in chemical 

 transformations, which belong to the domain of Mineralogy, and 

 relate to the crust, rather than to the body, of our globe. With- 

 out, therefore, wholly denying the cosmical importance of radium, 

 we calmly await developments which will show its correct place 

 in the order of nature. As the energy derived from radium would 

 counteract the efifects of secular cooling it may have greatly pro- 

 longed the history of the encrusted earth. 



12. In the investigation of phenomena so complex as those con- 

 nected with the physics of the earth, we must not expect the real 

 underlying physical cause to be entirely clear in every case, because 

 the present state of the globe presents to our contemplation natural 



