THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FIFTH SERIES.] 



OCTOBER 1899. 



XXXVI. Investigations in Capillarity : — The Size of Drops. — 

 The Liberation of Gas from Supersaturated Solutions. — 

 Colliding Jets. — The Tension of Contaminated Water- 

 Surfaces. By Lord Rayleigh, F.R.S.* 



The Size of Drops. 



fl 'H F relation between the diameter of a tube and the 

 J. weight of the drop which it delivers appears to have 

 been first investigated by Tate t, whose experiments led him 

 to the conclusion that " other things being the same, the 

 weight of a drop of liquid is proportional to the diameter of 

 the tube in which it is formed." Sufficient time must of 

 course be allowed for the formation of the drops ; otherwise 

 no simple results can be expected. In Tate's experiments 

 the period was never less than 40 seconds. 



The magnitude of a drop delivered from a tube, even when 

 the formation up to the phase of instability is infinitely slow, 

 cannot be calculated a priori. The weight is sometimes 

 equated to the product of the capillary tension (T) and the 

 circumference of the tube (27ra), but with little justification. 

 Even if the tension at the circumference of the tube acted 

 vertically, and the whole of the liquid below this level passed 

 into the drop, the calculation would still be vitiated by the 

 assumption that the internal pressure at the level in question 

 is atmospheric. It would be necessary to consider the 



* Communicated by the Author. 



t Phil. Mag. vol. xxvii. p. 176 (1864). 



Phil May. S. 5. Vol. 48. No. 293. Oct. 1899. 2 A 



