1912.] on the Origin. of Radium. 413 



is correct, that the present set of experiments can offer to the sohition 

 of the problem. With the experience ah'eady gained, especially in 

 dealing with large quantities of uranium and in the methods of mea- 

 surements of the minutest quantities of radium, there should l)e 

 no difficulty in obtaining and dealing with sufficient uranium, say 

 20 kilograms, of the requisite degree of purity as regards ionium 

 and radium, to determine directly in a few years the period of ionium 

 from the growth curve provided it is not greater than 200,000 years. 



A favourable opportunity is being awaited to initiate this large- 

 scale experiment. It requires a small room to itself in a permanent 

 institution uncontaminaLed with radium, and some guarantee that 

 once installed the preparations will remain undisturbed for a reason- 

 able term of years, and that the measurements will be continued in a 

 comparable manner should the period of life of the original investi- 

 gator prove insufficient. It is not enough to set aside a quantity of 

 uranium for our successors to see if any radium has grown in it. It 

 is essential that the exact form of the growth curve should be known 

 before the problem in question can be fully answered. There ma// be 

 more than one long-lived intermediate product between uranium and 

 radium. However, such indirect information as has been acquired 

 as to the life period of ionium indicates that it, alone, is sufficient 

 to account for the present results as regards the absence of growth of 

 radium from uranium. 



I desire to acknowledge my indebtedness to Mr. H. N. Beilby and 

 Mr. George Weller for their expert advice and help in overcoming 

 engineering difficulties encountered in the operation of the machine, 

 and to Mr. A. H. Bodle, the mechanic of the Chemistry Department, 

 for his skill and energy in constructing it. 



[F. S.] 



