September 30, 1910] 



SCIENCE 



443 



TABLE III 



Negative drop No. 8 

 Distance between cross hairs = 1.033 em. 

 Temperature = 20° C. 



.oinc 



Mean ej (weighted) = 5.482 



TABLE IV 



Negative drop No. 12 

 Distance between cross hairs ^ 1.005 cm. 

 Temperature =24.3° C. 



v^ = .01868 



Mean e^ (weighted) =5.349 



TABLE V 



Positive drop No. 15 

 Distance between cross hairs = 1.033 cm. 

 Temperature' = 20° C. 



.04265 



Mean e^ (weighted) =5.^08 



e,. This is illustrated by the observations 

 shown in tables 11., III., IV., V., VI. and VII. 

 The drops shown in tables II. and III. were 

 of almost exactly the same size, as is seen 

 from the closeness of the values of the two 

 velocities under gravity, and although the 

 field strength was in one case double that in 

 the other the values of e, obtained are almost 



TiVBLE VI 



Positive drop No. 16 

 Distance between cross hairs = 1.317 em. 

 Temperature :=27.6° C. 



.05360 



Mean e^ ( weighted ) ^= 5.143 



TABLE VII 



Negative drop No. 17 

 Distance between cross hairs = 1.305 cm. 

 Temperature = 26.8° C. 



ti = .05534 



Mean e^ (weighted) =5.145 



identical. Similarly tables VI. and VII. are 

 inserted to show the consistency which could 

 be attained in determining the values of e^ so 

 long as the drops used were of the same size. 

 On the other hand, the series of tables II., 

 IV., V. and VI. or III., IV., V. and VTI. show 

 conclusively that the value of e, 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. 



In order to find in just what way this law 

 breaks down we made an extended series of 

 observations upon drops the velocities of 



* The readings carried to hundredths of a second 

 were taken with a chronograph, the others with a 

 stop watch. The mean G from the chronograph 

 readings is 24.567, that from the stop-watch read- 

 ings 24.583. 



