DISTANCE EFFECTS. 



91 



Table 36. Distance effect and absorption of radium rays. D measured from side. 

 dp =31. November 2. Lead pipe 0.5 cm. thick, 60 cm. long 



II 



Above fog 



chamber . 

 On glass . . 



III. 



In lead pipe . 



On top . 

 At 00 . 



nx io" 



70 



42 

 32 

 27 

 24 

 49 

 135 



120 



100 



80 



60 



40 



20 



20 



40 



60 



80 



100 



120 



140 



160 



180 



200 



Fig. 46. Minima of efficient nucleations observed at high exhaustions with radium at 

 different distances (D) from the fog chamber. Table 36. 



62. Falling to pieces of ions in the lapse of time. Miss L. B. Joslin 

 contributes the following interesting observations obtained by the 

 method of depression of the terminal asymptote. 



The data summarized in table 37 and fig. 47 were obtained by acting, 

 in the manner stated, on the dust-free moist air contained within a glass 

 fog chamber, with a sample of weak radium (io.oooX, 10 mg.), sealed 

 in an aluminum tube. This was placed on the outside of the chamber 

 in contact with its walls (0.2 to 0.3 cm. thick), and was then removed 



