748 Dr. Bottomley and Mr. King : Experiments ivith 



Experiment 1. — The first indications which presented them- 

 selves to us, of the existence of the peculiar effects which we 

 are ahout to describe, were obtained while we were experi- 

 menting with a "radium clock," constructed much as described 

 by the Hon. E. Strutt, F.B.S.* (PL XVII.) We have set 

 up this apparatus for the purpose of carrying out secular 

 observations, and in order to find, if possible, whether the 

 activity of the radium seems to diminish with time. 



Quartz rod 



To Sprengel 



The radium clock, as is well known, is practically a gold-leaf 

 electroscope, contained in an outer vessel highly exhausted, 

 in which a small glass tube containing some radium, and with 

 its outer surface smeared with an aqueous solution of phos- 

 phoric anhydride, to render it conducting, is connected 

 metallically to the gold leaves. 



Two metallic plates, with connexions passing to the out- 



* Strutt, Phil. Mag. Nov. 1903 ; Rutherford's ' Radio-activity/ 2nd 

 edition, p. V22 



