in Gases by the Motion of Negitimly Ch%rged Ions. 635 



When this point was reached, the determinations of current 

 were first made for the smaller forces with a suitable strength 

 o£ rays. The set of determinations at the fixed pressure was 

 continued for higher forces with the rays reduced to a fraction 

 of their original strength. The first observation in the second 

 series was made with the same force as the last observation in 

 the first series, in order to find the amount by which the rays 

 were reduced. The numbers tabulated are the observed 

 currents multiplied by a factor, and represent the currents 

 which would have been obtained if the rays had been left at 

 the same strength throughout. The last six numbers in 

 experiment 3 in the following table were obtained in this 

 way. 



Table IV. — Currents in Carbonic Acid Gas. 

 Plates 5 millimetres apart. 









Pressures. 









X. 

































133 



8-8 



395 



1-4 



•68 



•25 



-097 



76 



140 



35 



19-6 



76 



5-25 



5-3- 



... 



152 



141 



355 





10-8 



8-1 



7-8 





228 





..... 







136 





.... 



304 



.... 





33 



30-8 



20 



... 





380 







48 



544 



29-3 







456 







75 



95-7 



40--2 



li'-i 



195 



532 



153 



64 



126 



162 



52-9 







608 





88 



216 



250 



72 



16 V 2 





684 





129 



420 



411 



99 







760 



198 



195 



778 



660 



161 



19* 





836 



232 



302 



1460 











912 



286 



530 



2830 







213 



235 



972 



337 



850 



4330 











1032 



395 



1290 



8300 









7. 





1. 



2^ 



~~37~ 



4. 



5. 



6. 



3. We have found from these observations the number of 

 ions, a, that a single ion generates in going one centimetre in 

 a gas at pressure p under an electric force X. When the 

 temperature is constant a is a function of X and p. 



If n negative ions are distributed uniformly between two 

 plates, and a force X perpendicular to the plates acts on them, ■ 

 the total number which reach the positive plate is 



€« l -l 



n - 



cd 



I being the distance between the plates. 



* J. S. Townsend, ' Nature/ 9th Aug. 1900. 

 2T2 



