THE MOBILITY OF LARGE IONS IN THE AIR. 65 



Table I. 









ELECTROMETER. 





1908, 



Air stream 



Volts. 







Corrected 



March 26. 



cc. per sec. 





Sees, per cm. 



Mean. 



reciprocal 

 cms. per sec 



a.n:. 













9-55 



48-8 

 



50 



21, 23, 24, 22, 



20, 21, 22. 

 + 95 



22 



•0350 



10-15 



49-7 

 



100 



15, 15, 15, 15-6 



+ 187 



15-1 



•0609 



10-30 



48-8 

 



200 



10, 10, 10, 10, 

 + 250 



10 



•0960 



10-55 



51-5 

 



300 



8-8, 8-4, 8-4, 8-2, 

 + 250 



8-45 



•1143 



11-20 



50-6 

 



300 



8-4 

 + 200 



8-4 



•1140 



11-30 



51-5 







350 



8-6 

 + 560 



8-6 



•1145 



11-45 



51-5 







300 



8-2, 7-8, 8-6, 

 8-2, 8-4, 8-4. 



+ 225 



8-6 



•1118 



120 



51-5 







250 



8-6, 8, 8-8, 8-8. 

 + 196 



8-55 



•1118 • 



12-10 



51-5 







200 



10, 10, 10-2, 

 10, 10, 10. 



+ 220 



10 



•0955 



1230 



50-6 

 



150 



12-2, 12-2, 12-2. 

 + 180 



12-2 



•0764 



12-45 



51-5 

 



100 



14-2, 13, 14, 13-8, 



14-4 



+ 106 



13-9 



•0625 



3. The mobility of the large ions.— To reduce the humidity, 

 the air, before entering the testing pipe, was passed through 

 tubes, five centimetres in diameter, containing calcium 

 chloride. The humidity of the dried air was determined by 

 a series of independent measurements giving the amount 

 of moisture absorbed by phosphorus pentoxide from the air 

 as it escaped from the testing pipe, the strength of the air 

 earn being the same as in the experiments for hading 

 the mobility. It is impossible to observe the humidity in 

 this way for each determination of the mobility, and for 

 each set of circumstances a result has been calculated from 



E— June 2, 1909. 



