[KENNEDY] 



ACTIVE DEPOSIT FROM ACTINIUM 



63 



and uncharged deposit particles involved in any particular measurements. 

 With the object of throwing one light on this point an additional set of 

 observations was made on the deposits obtained in air at different pres- 

 sures with the electrodes uncharged, and at a distance of 3 mm. apart. 

 The activities obtained on the two electrodes in these experiments were 

 added together and the numbers representing them are given in Table 

 VIII. For purposes of comparison the total activities obtained with air 

 at different pressures under a field of 250 volts are also inserted in the 

 table and curves representing both sets of values are shown in Fig. XIV. 

 From an inspection of the two curves it will be seen that the total active 

 deposit was practically the same with and without the field at all pres- 

 sures above the critical one. At and below this pressure the deposits 

 obtained with the electric field applied, as the figure shows, were some- 

 what in excess. From this experiment it would seem that the deposit 

 particles in very great measure go to the walls of the vessel in which they 

 are produced whether an electric field be applied or not. 



TABLE VIII 



The manner in which they are carried there, however, is not evident. 

 It is possible that a certain proportion of the deposit particles are 

 uncharged and that these reach the walls by ordinary diffusion. 

 Then again, these deposit particles may be electrically charged, some 

 of them being of one sign, and some of the opposite, and diffusion again 

 may be the chief factor in producing the deposit, or further, if the dis- 

 integration recoil phenomenon is the determining factor it is possible 

 that, with the plates close together, the deposits are made by reason of 

 the velocity of expulsion alone. If this latter be the explanation the 

 sign of the charge carried by the deposit particle would not then exert 

 any considerable influence except in the most intense fields. 



In all the measurements made the cathode deposit was, except at 

 the very lowest pressures, considerably in excess of that obtained on the 



