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



Thus while we confined our estimates and calculations to gravita- 

 tional energy, we do not deny the possibility that other sources of 

 energy of an atomic or radioactive character may exist. If such 

 sources really exist, the effect would be to prolong the period of the 

 earth's history since consolidation. 



At the present it is impossible to estimate these effects with any 

 approach to accuracy, and we have therefore preferred to await the 

 results of future research. 



Our knowledge of radium and the role it plays in cosmical de- 

 velopment is still much too limited to permit even a rough estimate 

 of the effects of such subatomic energy. But it seems certain that 

 radium has no sensible connection with volcanic eruptions, since in 

 the rocks underlying the great extent of the continents it remains 

 quiescent, and gives rise to no kind of outbreaks, though it may 

 raise slightly the temperature of certain mineral springs. Remark- 

 able as radium is, and wonderful as are its chemical actions, we are 

 still unable to say that it plays any sensible part in cosmical processes 

 outside of chemical transformations which lie in the domain of 

 Mineralogy. The energy liberated in these transformations might, 

 however, greatly prolong the past history of the earth, and the total 

 duration might thus be extended from 10 to 100 million years. 



III. On the Disturbances of the Earth's Magnetism by 

 Earthquake and Volcanic Phenomena. 



§ 19. Observations Show That Earthquakes and Volcanic Out- 

 breaks Often Disturb Terrestrial Magnetism. — It has long been 

 noticed that volcanic outbreaks and also earthquakes are not infre- 

 quently accompanied by temporary disturbances of the earth's mag- 

 netic field. The cause of this is not yet understood and any con- 

 jecture at this time may be premature, nevertheless we are inclined 

 to call attention to certain features of these phenomena which should 

 be borne in mind. 



I. As the earth's crust is thin, and the interior at an immense 

 temperature, it seems highly probable, if not certain, that the mag- 

 netism of the globe depends upon the crust and the atmosphere, 

 together with the sun's variable magnetic field in which our planet 



