142 THE NEW KNOWLEDGE. 



ounce of any uranium compound at any time possesses, is 

 due simply to this uranium X existing therein, the quan- 

 tity of which depends on a balance between ^the rate at 

 which it decays and the rate at which the uranium manu- 

 factures it. 



We may attempt to illustrate this mechanism by con- 

 structing a crude analogy. 



Let us suppose that we have a full-grown sweet-pea vine 

 and that the vine is the uranium. 



The tendrils of the vine are the alpha-rays from uranium. 



The flowers are uranium X. 



The scent of the flowers are the beta-rays from ura- 

 nium X. 



Let us suppose, moreover, that we leave the vine strictly 

 alone. We can easily see that there will come a time in 

 our garden when the flowers of the vine will decay as fast 

 as the vine produces them, and that the total number of 

 flowers on the plant will depend upon a balance between 

 their rate of growth and decay. Similarly, there comes a 

 time with the uranium, when the amount of uranium X pro- 

 duced decays as fast as the uranium produces it, and the 

 total amount of uranium X in the uranium depends upon 

 a balance between its rate of growth and decay. If we 

 were working with our flowers in the dark as we are, met- 

 aphorically speaking, with our uranium, we might estimate 

 their number by picking them out by their scent; we do 

 estimate the amount of uranium X formed by the amount 

 of its beta-rays. Now, let us suppose that some dewy 

 morning we snipped off every flower; in other words sup- 

 pose we extract the uranium X from the uranium. We 

 now have the flowers with their scent in one hand, and 

 the uranium X with its beta-rays in the other. There re- 

 mains the destitute vine with its tendrils and the destitute 



