1893.] Gravity of Fluid Bubbles through Liquid* 



TABLE V. 



17 



The agreement with theory is remarkable, considering the great 

 range introduced into the experiments. The density difference and 

 the surface tension vary between themselves nearly 100 times. 



In the accompanying diagram are plotted the various forms the 

 equation takes on putting in the values of the physical constants 

 proper to each body. The abscissas represent the diameter of the 

 tube in millimetres, and the ordinates the time calculated to be taken 

 by the bubble in travelling 1 cm. The times found by experiment 

 given in the above tables are marked so far as the limits of the paper 

 would allow for the purpose of comparison. 



The case of creasote is instructive. With wide tubes the bubble 

 moves comparatively slowly. For when the diameter is large, the 

 first term in the series is most important, so that the density is then 

 the controlling factor. But when D is small, the third term is most 

 important, so that if the surface tension is very small, as is so in the 

 case of creasote, the bubble will move comparatively quickly. 



In such case the bubble assumes a long, almost needle-like appear- 

 ance, giving ample room round it for the flow past of the liquid of 

 the column. In the case of chloroform, for instance, this long form 

 is not assumed because of the higher value of the surface tension. 



The following table exhibits, in the case of several substances, the 

 length of the bubble in motion relatively to its length at rest, when, 

 of course, it occupies the whole width of the tube. The diameter of 

 tube = 0-665. 



Table VI. 



Mercury .... 

 Air 



Oil of lemons 

 Chloroform . 

 Creasote .... 



1-8 

 1-2 



1-8 

 1-4 



2-0 



VOL. LIV. 



