616 APPLIED MATHEMATICS 



of gravity, we no longer know even what this is. This is why I 

 said above that the experiments on the cathode rays appeared to 

 justify the doubts of Lorentz on the subject of the principle of 

 Newton. 



From all these results, if they are confirmed, would arise an 

 entirely new mechanics, which would be, above all, characterized by 

 this fact, that no velocity could surpass that of light, any more than 

 any temperature could fall below the zero absolute, because bodies 

 would oppose an increasing inertia to the causes, which would tend 

 to accelerate their motion; and this inertia would become infinite 

 when one approached the velocity of light. 



Nor for an observer carried along himself in a translation he 

 did not suspect could any apparent velocity surpass that of light; 

 there would then be a contradiction, if we recall that this observer 

 would not use the same clocks as a fixed observer, but, indeed, clocks 

 marking "local time/' 



Here we are then facing a question I content myself with stating. 

 If there is no longer any mass, what becomes of the law of Newton? 



Mass has two aspects, it is at the same time a coefficient of iner- 

 tia and an attracting mass entering as factor into Newtonian attrac- 

 tion. If the coefficient of inertia is not constant, can the attracting 

 mass be? That is the question. 



At least, the principle of the conservation of energy yet remains 

 to us, and this seems more solid. Shall I recall to you how it was 

 in its turn thrown into discredit? This event has made more noise 

 than the preceding and it is in all the records. 



From the first works of Becquerel, and, above all. when the 

 Curies had discovered radium, one saw that every radio-active body 

 was an inexhaustible source of radiations. Its activity would seem 

 to subsist without alteration throughout the months and the years. 

 This was already a strain on the principles; these radiations were in 

 fact energy, and from the same morsel of radium this issued and for- 

 ever issued. But these quantities of energy were too slight to be 

 measured; at least one believed so and was not much disquieted. 



The scene changed when Curie bethought himself to put radium 

 into a calorimeter; it was seen then that the quantity of heat in- 

 cessantly created was very notable. 



The explanations proposed were numerous; but in so far as no 

 one of them has prevailed over the others, we cannot be sure there 

 is a good one among them. 



Sir William Ramsay has striven to show that radium is in process 

 of transformation, that it contains a store of energy enormous but 

 not inexhaustible. 



The transformation of radium, then, would produce a million 

 times more of heat than all known transformations; radium would 



