THOUGHTS ON NATURAL PHILOSOPHY. 43 



It is this energy which I have designated by the 

 term intra-atomic energy. What are its fundamental 

 characteristics ? It differs from all forces known to 

 us by its very great concentration, by its prodigious 

 power, and by the stability of the equilibria it can 

 form. We shall see that, if instead of succeeding in 

 dissociating thousandths of a milligramme of matter, 

 as at present, we could dissociate a few kilogrammes, 

 we should possess a source of energy compared with 

 which the whole provision of coal contained in our 

 mines would represent an insignificant total. It is 

 by reason of the magnitude of intra-atomic energy 

 that radio-active phenomena manifest themselves 

 with the intensity we observe. This it is \vhich 

 produces the emission of particles having an immense 

 speed, the penetration of material bodies, the appari- 

 tion of X rays, etc. 



The following figures will show that, whatever be 

 the method adopted, we arrive, by measuring the 

 energy liberated by a given weight of dissociated 

 matter, at totals immensely superior to all those 

 obtained by hitherto known chemical reactions the 

 combustion of coal, for example. It is for this 

 reason that substances, in spite of the slightness of 

 their dissociation, are able to produce during this 

 phenomenon the intense effects which I have to 

 enumerate. 



The different methods in use for measuring the 

 speed of the particles of dissociated matter, whether 

 radium or any metal whatever, have always given 

 nearly the same figures. This speed is almost that 

 of light for certain radio-active emissions. For 



