OF ARTS AND SCIENCES. 131 



X. 



coxTRiBUTioxs feo:m physical laboratory of har- 

 vard COLLEGE. 



No. XIi: — ON VORTEX RINGS IN LIQUIDS. 

 By Joiix Trowbridge. 



Presented, March 14, 1877. 



It has often been observed by chemists that a drop of colored liquid 

 falling from a burette into a liquid of a different specific gravity, in 

 which it can diffuse, assumes tlie form of a ring. Vortex motion, by 

 the researches of Helmholtz, Thomson, Rankine, and Maxwell, is now 

 attracting so much attention, that I have thought that a study of the 

 general equations of motion of matter in connection with a study of 

 these rings would contribute to our knowledge of vortex movement. 



Prof. W. B. Rogers publislunl in " The American Journal of Arts 

 and Sciences," Vol. XXVI., 1858, a paper on smoke rings and liquid 

 rings, and described several methods of studying them. In Professor 

 Tait's " Recent Advances in Physical Science," a method of forming 

 smoke rings is given. The apparatus consists merely of a large box 

 closed at one end by a thin sheet of India rubber, or with a tightly 

 stretched towel, and having a circular opening of six or eight inches 

 in diameter at the other. Clouds of sal-ammoniac vapor are generated 

 inside the box, and rings are expelled from the circular opening by a 

 blow upon the rubber or towel. Sir William Thomson suggests that 

 two such boxes placed so that the rings may impinge on each other at 

 any angle would form a useful apparatus for studying the behavior 

 of such rings towards each other. At the conclusion of this paper, 

 several metiiods of studying liquid rings will be described. When a 

 drop of liquid falls from a short distance into a liquid of less density, 

 in which it cannot diffuse, the conditions of its motion just after the 

 instant of its striking the surface of the liquid of less density are 

 indicated by the general equations of heterogeneous strains.* " For 



* Thomson and Tait's ivatural Philosophy. 



