334 Lord Bayleigh : Investigations in Capillarity. 



It is of interest to inquire what point on these curves cor- 

 responds to the deadening of the movements of small particles 



Figs. S-G. 



12 3 4 5 6 



















F 



a(3) 



„ 





FIG (4- 



) y. 



c 



























F 



IG(S)~~ 





r\ 









c 





FIG (6 

















of camphor deposited upon the surface. On a former occasion 

 \ have shown (Phil. Mag. vol. xxxiii. p. 366, 1892) that 

 whatever may be the character of the grease the cessation of 

 the movements indicates that the tension falls short of a 

 particular value. In the present method of experimenting 

 there is no difficulty in determining what for brevity may be 

 called the camphor-point. Two precautions should, however, 

 be observed. It is desirable not to try the camphor until near 

 the close of a set of experiments, and then to avoid too great 

 a quantity. It would seem that the addition of camphor may 

 sometimes lower the tension below the point due to the grease. 

 The second precaution required is the raising of the balanced 

 strip ; otherwise wbeu a weight is taken the density of the 

 grease is altered. In several trials with castor and other 

 oils the camphor-point was found to correspond with a drop 

 of tension from that of clear water amounting to '9 gm. The 

 points thus fixed are marked in figs. (3) and (4) with the 

 letter C. 



At this stage a certain discrepancy from former results 

 should be remarked upon. Working by the method of 

 ripples I had concluded that the camphor-point corresponded 

 to a tension *72 of that of pure water, i. e. to a drop of 28 

 per cent. But the - 9 gm. is only 22 per cent, of the calcu- 

 lated weight for pure water, i. e., 4'Tgms. At this rate the 



