42 THOUGHTS ON NATURAL PHILOSOPHY. 



give a small bullet the speed of the particles emitted 

 by matter in process of dissociation would require a 

 firearm capable of containing one million three hun- 

 dred and forty thousand barrels of gunpowder. As 

 soon as the immense speed of the particles emitted 

 was measured by the very simple methods I describe 

 elsewhere, it became evident that an enormous 

 amount of energy is liberated during the dissociation 

 of atoms. 



The radio-activity is above all manifested under 

 the influence of external agents light, heat, chemical 

 forces, etc. it is comprehensible that we should seek 

 for the origin of this proved energy among these 

 external causes, though there is no comparison 

 between the magnitude of the effects produced and 

 their supposed causes. As to spontaneously radio- 

 active bodies, no explanation of the same order was 

 possible, and this is why the question set forth above 

 remained unanswered and seemed to constitute an 

 inexplicable mystery. Yet, in reality, the solution to 

 the problem is very simple. Let us first of all remark 

 that it is proved by experiments that the particles 

 emitted during dissociation possess identical char- 

 acteristics, whatever the substance in question and 

 the means used to dissociate it. Whether we take 

 the spontaneous emission from radium or from a 

 metal under the action of light, or again from a 

 Crookes' tube, the particles emitted are similar. The 

 origin of the energy which produces the observed 

 effects seems therefore to be always the same. Not 

 being external to matter, it can only exist within 

 this last. 



