PERPETUAL MOTION. 



is repeated and followed once more by their 

 falling together. 



This process is apparently able to go on 

 indefinitely not merely for months, but for 

 years and for generations. 



And there is no fresh motive power supplied 

 to keep up the movement. No fuel is burnt, 

 no dynamo driven, no friction made, no 

 mechanical motion given to the apparatus. 



Here, then, it looks as if we had another 

 form of perpetual motion. 



The apparatus is called a clock because of 

 the regular intervals at which the movement 

 of the leaves takes place, as with the pendulum 

 beats of a clock ; and with enough radium 

 to work the machine on a large scale, no doubt 

 it could be made to record the time on a dial. 



As for the motion being perpetual, it is 

 not so. The accepted theory is, as stated, that 

 some of the atoms are constantly undergoing 

 disintegration, and, as radium, disappearing ; 

 and by the amount of that loss the quantity 

 left behind is diminished. True, the loss is so 

 small (surprisingly small, in view of the effects 

 produced), that it cannot be measured by 

 balances or other tests. 



It is calculated, however, that it is fast 

 enough for half of the radium to have dis- 

 appeared in about a thousand years ; so that a 

 clock of this kind started in the year A.D. i 

 would now be^going at about quarter speed. 



183 



