ISOLATION OF AN ION MILLIKAN. 



247 



tical. Similarly Tables VII and VIII are inserted to show the con- 

 sistency which could be attained in determining the values of e x 

 so long as the drops used were of the same size. On the other hand, 

 the series of Tables III, V, VI, and VII, or IV, V, VI, and VIII, 

 show conclusively that the value of e x obtained in this way diminishes 

 as the velocity of the drop increases. This means of course that 

 Stokes's law does not hold for these drops. 



Table VII. — Positive drop No. 16. 

 [Distance between cross hairs= 1.317 cm. Temperature = 27.6° C] 



Table VIII. — Negative drop No. 17. 

 [Distance between cross hairs= 1.305 cm. Temperature = 26.8° C] 



1 The reading carried to hundredths of a second were taken with a chronograph, the 

 others with a stop watch. The mean O from the chronograph readings is 24.567, that 

 of the stop-watch readings 24.583. 



In order to find in just what way this law breaks down we made 

 an extended series of observations upon drops the velocities of which 

 varied in the extreme case 360 fold. These velocities lay between 



