DISTANCE EFFECTS. 



89 



340 



e?o 



zoo 



ISO 



160 



140 



120 



too 



O 100 ZOO 300 400 SOO 600 



Fig. 44. Nucleations (ions) produced by a radi- 

 ating X-ray bulb at different distances (D) 

 from the large wood fog chamber. Table 34. 



61 . Distance effect and absorption. Radium. A few experiments were 

 made incidentally with impure radium (10 mg. io.oooX, sealed in 

 aluminum), using the method of depression of the terminal asymptote. 

 In table 36, for instance, results are recorded on the absorption of the 

 y-rays in lead. Fig. 45 shows the results in relation to the nucleation of 

 dust-free air, the efficient nucleation of which is more and more reduced 

 as the intensity of the radiation increases with the diminishing thickness 

 of the absorbing lead envelope. 



After nearly 1.6 cm. of lead have been penetrated, the distance of the 

 curve from the asymptotic air line is still marked. Results of this kind 

 should furnish valuable data for testing any theory on the distribution 

 of precipitated moisture on graded nuclei under any definite conditions. 



Table 36 gives an incidental series of distance effects worked out by 

 the same methods. As exhibited in fig. 46, the first series reaches the 



