V] OF FALLING DROPS 395 



the drop becomes a jet; the, form of the vortex is modified thereby, 

 and may be further modified by sHght differences of temperature 

 (i.e. of density), or by interrupting the rate of flow. To let a drop 

 of ink fall into water is a simple and most beautiful experiment*. 

 The effect is more violent than in the former case. The descending 



Fig. 120. Falling drops. A, ink in water, after J. J. Thomson and Newall. 

 B, fusel oil in paraffin, after Tomlinson. 



drop turns into a complete vortex-ring ; it expands and attenuates ; 

 it waves about, and the descending loops again turn into incipient 

 vortices (Fig. 120). 



Lastly, instead of letting our drop rise or fall freely, we may use 

 a hanging drop, which, while it sinks, remains suspended to the 

 surface. Thus it cannot form a complete annulus, but only a 



* J. J. Thomson and H. F. Newall, On the formation of vortex-rings by drops, 

 Proc. R.S. XXXIX, pp. 417-436, 1885. Emil Hatschek, On forms assumed by a 

 gelatinising liquid in various coagulating solutions, ibid. (A) xciv, pp. 303-316, 1918. 



