120 Proceedings of Royal Society of Edinburgh. [sess. 
pitch. The results obtained so far are not sufficient to enable any 
accurate comparison to be made, but they show that if there is any 
effect produced by the surface-flexure rigidity it must be very small 
compared with that due to surface-tension. 
The following table gives the actual results for mercury at a 
mean temperature of about 12° C. 
Vibrations per 
Second. 
A. 
Centimetres. 
T 
Dynes per 
Centimetre. 
768 
0-0745 
528 
3 3 
0*0746 
531 
Average 
529-5 
512 
0-0980 
534 
0-0971 
519 
Average 
526-5 
256 
0-157 
546 
0*154 
517 
Average 
531-5 
Average for the whole, 529. 
Two photographs were taken for water, but in each of them only a 
few waves could be measured, so that no great weight can be placed 
on the result. They were both with the fork giving 256 vibrations 
per second, and the resulting wave-lengths were 0*195 and 0*208 cm., 
corresponding to the values of 77 and 94 for T. The mean is 85*5, 
while Quincke’s value is 81. 
A photograph of a mercury surface covered with dilute sulphuric 
acid gave A = 0*141 for 256 vibrations per second. If we neglect 
all influence of the acid other than in changing the surface-tension, 
this would give T = 400, or practically the same as for water and 
mercury. 
Two photographs were taken of a surface of mercury charged to 
a high potential by means of a Holtz electric machine. The photo- 
graphs gave very consistent measures : — 
No. 43. 256 v.p.s. Average of 58 waves A = 0T43 . . T = 417. 
No. 44. 256 v.p.s. Average of 30 waves A = 0"144 . . T = 425. 
So that it is evident that electrification produces a considerable 
