50 THOUGHTS ON NATURAL PHILOSOPHY. 



To fix our ideas, let us suppose a small bronze sphere 

 (density 8.842), with a radius of three millimetres and 

 consequently of one gramme in weight. Let us 

 suppose that it rotates in space round one of its 

 diameters with an equatorial speed equal to that of 

 the particles of dissociated matter (100,000 kilometres 

 per second), and that, by some process or other, the 

 rigidity of the metal has been made sufficient to resist 

 this rotation. Calculating the vis viva of this sphere 

 it will be seen to correspond to 203,873,000,000 kilo- 

 grammetres. This is nearly the work that 1,510 

 locomotives averaging 500 h.p. apiece would supply 

 in an hour. Such is the amount of energy that could 

 be contained in a very small sphere animated by a 

 rotatory movement of which the speed should be 

 equal to that of the particles of dissociated matter. 

 If the same little ball turned on its own centre with 

 the velocity of light (300,000 kilometres per second) 

 which represents about the speed of the B particles 

 of radium, its vis viva would be nine times greater. 

 It would exceed 1,800,000,000,000 kilogrammetres 

 and represent the work of one hour by 13,590 

 locomotives, a number exceeding all the locomotives 

 on all the French lines. 



It is precisely these excessively rapid movements 

 of rotation on their axis and round a centre that the 

 elements which constitute the atoms seem to possess, 

 and it is their speed which is the origin of the energy 

 they contain. We have been led to suppose the 

 existence of these movements of rotation by various 

 mechanical considerations much anterior to the dis- 

 coveries of the present day. These last have simply 



