E. M. Wellisch — Mobilities of Ions in Air. 591 



words, the electrode e begins to receive a negative charge with 

 a very small potential applied to the gauze. Moreover, the 

 curve E is exactly the type which we would expect to obtain 

 if it were due to a single constituent, i. e., if the electric 

 charges which correspond to it were carried by a carrier of a 

 definite nature. This point is borne out by a reference to the 

 curve of fig. 6 which gives the relation between the current 

 due to positive ions and potential of the gauze, when the latter 



Fig. 5. 



20 



15 



10 



















T3 















#/ 





















j 





















// 









i^ 

















/ 



















^y 







E 















/ 



















V 

















20 



40 



60 



80 



100 



Volts 



is direct (i. e. there are no alternations). The potential in the 

 antechamber was as usual 20 volts, the pressure was 17 , 39 mm 

 and the current was measured with the capacities B and C 

 added to the system. This was the type of curve obtained in 

 all cases when a direct field was employed ; the continued up- 

 ward slope of the curve at the higher potentials is due to the 

 fact that as the potential is increased a larger number of ions 

 are pulled out from the region above the gauze. The curve E 

 of fig. 5 is thus exactly of the nature which we would expect 

 to arise from a single type of carrier and may in consequence 

 be regarded as being due entirely to free electrons. The curve 

 marked I is similarly due to a single type of carrier, but one 

 which moves with a smaller mobility; for this reason, this 



