770 



Mr. H. D. Arnold on Stokes's Law for 



called B, it follows on the assumption of Stokes's law that 

 the radius of the constant sphere which would have traversed 

 the distance in equal time is given by 



.. „ 1-B 



In fig. 7 the curve r 2 - shows the squares of the radii, and 



7 8 9 10 I! 12 13 



D /stance Traversed in Meters 



curve Y the velocities of a bubble of air in olive oil. The 

 consistency of the observations allows a very accurate com- 

 putation of the apparent viscosity. In fig. 8, curve I. shows 

 the values of fju computed from the simple form of Stokes's 

 law, and curve II. shows the corresponding values after 

 applying Ladenberg's correction. The upper and lower 

 straight lines give respectively the values of jn and of 2/3 jx 

 from capillary tube measurements, the upper corresponding 

 to no slip and the lower to infinite slip. It will be noticed 

 that the observed values lie wholly within these latter two 

 lines. 



Fig. 9 shows similarly the results of an experiment with 

 linseed oil. The observed values fall but slightly below 

 those obtained with the capillary tubes, in marked contrast 

 to the results with olive oil. 



The curves of figs. 8 and 9 are typical of those obtained 

 with all the liquids used. It would appear that in liquids of 

 the type of olive oil the coefficient of slip is a function of the 



