Duane — Emission of Electricity. 



9 



above described experiments. In one case the electrode A was 

 made active exactly as before, placed in position in tnbe B and 

 the currents measured at atmospheric pressure instead of in 

 vacuum by means of the piezo-electric quartz. Column 3, 

 Table III contains the results reduced to the same scale as those 

 in column 2 for £=70. It appears that they by no means 

 coincide except for £=70. In fact the data of column 3 repre- 

 sent points that would lie much more nearly on the theoretical 

 curve 3 (figure 2) than on curve 1. This can be due only to 

 the ionizing eifect of radium B, and indicates that within a J mm 

 of the surface the rays from radium B produce ionization com- 

 parable with that produced there by the rays from radium C. 

 This large ionization would be explained, if radium B produced 

 a rays having a velocity just greater than the critical velocity 

 required to produce ions. Such an hypothesis, however, is not 





Table III. 





Time in 



Current in 



Current in 



minutes 



large con. 



small tube 



10 



3*01 



415 



12 



2-97 





15 



2-91 



3'84 



17 



2*86 





20 



2-83 



3-53 



25 



2-76 



3-30 



30 



2-54 



3-09 



35 



2-38 



2-89 



40 



2-26 



2-64 



45 



2-04 





50 



2*01 



2-11 



55 



1-83 





60 



1-70 



1-80 



65 



i'58 



1-59 



70 



1-42 



1-42 



75 



1-31 





absolutely Required by the facts, and would contradict some 

 results obtained by Bronson.* 



16. In order to estimate the velocity with which the carriers 

 of electricity are projected from the metallic surfaces the brass 

 electrode and tube were placed between the poles of an electro- 

 magnet and a magnetic field of 996 units produced parallel to 

 their common axis. The currents were measured alternately 

 with and without the field to correct for their decay during 

 the experiments. The measurements indicate that both the 

 positive and negative currents and also their algebraic sums are 

 diminished by the magnetic field. According to the well- 

 * Bronson, Phil, Mag. (6), xi, 806-812, 1906. 



