MISCELLANEOUS EXPERIMENTS. 



A few rain limits were incidentally tested, as the opportunities were 

 exceptionally good. These data are given in part III of the table. They 

 have the usual values in my work, dp/p = o.2^ orv l /v=i.2i, and lie below 

 Wilson's values. 



40. Distance effect. A few experiments w y ere incidentally made to 

 determine the effects of the distance D of the radium from the fog chamber 

 in terms of the numbers of ions produced per second, a, where a = bri 2 + cn, 

 as above explained. The method of two sources (chord 5) with the 

 coronas in contact was used. Table 18 shows the chief results. 



TABLE 18. Distance effect. Radium I to V. Barometer 76.4; temperature 21.6. 

 D from axis of fog chamber. Air, 5=1.0. 8p 3 =22.8; dp/p 3 = o.2g8; 6=io~ 9 ; 

 = 0.0356. 



*Radium tube lies on the glass vessel, 7 cm. from the axis. 



Inferring that w 2 D 2 (i + c/6w) should be constant, the following com- 

 parison results: 



D = 7 20 50 loo 200 cm. 



10 l2 w 2 Z? 2 (i + c./bn) =* 1.7 5.2 7.4 4.6 7.2 



At D 7 cm. the radium is too close for any law. The agreement there- 

 after is an attempt at constancy in so far as the small coronas beyond 

 D < TOO cm. admit. 



41. Attempt to calibrate the fog chamber with 5 separate sealed tubelets 

 (I, II, III, IV, V) of radium. These results are given in table 19. The 

 tubes were placed in a gutter on the outside of the chamber at a dis- 

 tance D, or in a sealed aluminum tube within the chamber. The 

 table gives the aperture 5 (two sources of light), the nucleation n com- 

 puted therefrom and the number of ions a generated per second, where 

 a = bn t -\-cn as in the preceding instance. 



