I. 



MECHANICS AND RADIUM. 



I. 



Introduction. 



Are the general principles of Dynamics, which have 

 served since Newton's day as the foundation of Physi- 

 cal Science, and appear immutable, on the point of 

 being abandoned, or, at the very least, profoundly 

 modified ? This is the question many people have 

 been asking for the last few years. According to 

 them the discovery of radium has upset what were 

 considered the most firmly rooted scientific doctrines, 

 the impossibility of the transmutation of metals on the 

 one hand, and, on the other, the fundamental postu- 

 lates of Mechanics. Perhaps they have been in too 

 great haste to consider these novelties as definitely 

 established, and to shatter our idols of yesterday ; 

 perhaps it would be well to await more numerous 

 and more convincing experiments. It is none the less 

 necessary that we should at once acquire a knowledge 

 of the new doctrines and of the arguments, already 

 most weighty, upon which they rely. 



I will first recall in a few words what these prin- 

 ciples are. 



