Noi>AN — fons produced in Air hij Nadio- Active Bodien. 43 



Confirmation. 



Tlie foregoing results were obtained by the .lutlior early in 1918. Tt 

 was ditticiilt, however, to believe that, if the ordinary small ion were in 

 reality a mixture of what might be termed " isotopes," the fact should not 

 have been detected by other observers. Efforts were therefore made to 

 obtain confirmation of this result by an entirely different method. 'J'his 

 has presented many difficulties, which have not yet, in fact, been completely 

 surmounted. But some degree of confirmation has been obtained so far as 

 concerns tilie four principal groups. It is hoped to give at a future date 

 some account of these experiments ; their value so far lies only in the fact that 

 they support the much more distinct evidence given by the method described 

 above. 



General CoNsinEiiATiONS. 



These efforts to obtain independent confirmation liave delayed the 

 investigation of certain points which at once present themselves as objecls 

 of inquiry. For example, an inspection of fig. 3 shows that there appears to 

 be considerable difference between the mobility of the slowest positive ion 

 and that of the corresponding negative ion. It is important to finil out 

 whether this is a real difference. Sufficient observations have not yet been 

 made to decide the point. A table is given setting out the results of all good 

 observations made so far on the four principal groups. The corresponding 

 values found in the previous work on spray-ions are also given. 



'J'ABMi; OF Moiui.ri'Y OF Jons. 



Radio-activj'. SOUIICE. 



Negative. 





I'lisiiive 



2-0 1-92 



— 



2-07 



1-78 1-6-1 



1-74 



1'78 



1-54 1-47 



1'50 



1-59 



1-3G 1-33 



1-30 



1-45 



Sr 



KAY 

 /v_ 



Ions. 



Nei;ative 





l^osilive. 



1-94 





1-93 



1-70 





1-72 



1-49 





1-56 



1-34 





1-37 



Tbe values given Ijy the graph \\\ fig. 2 for the nKirc nitibile inns, ihat is, 

 12'5, 6'66, 4 16, and 3'0, are in good agreement with the other observations 

 which have so far been made over that range. 



Another very important point is the question of humidity. All these 

 observations have been made on moist air. An exaniinatinn of tlie changes 

 in the distribution of the iuns produced by drying should be of great 

 interest, 



