STUDIES OF VORTEX-RINGS. 



179 



not a glass tube at hand, we may make the communication by means 

 of a tine bird's-quill, or a thin straw of grass, or even by a pinhole 

 pierced in a piece of membrane. Having brought the orifice and the 

 surface of separation of the two liquids to the same level, if we give a 

 gentle push, we may see issue a kind of swelled fungus with a short 



Fig. 3. Arrangement op an Apparatus for the Study of Vortical Veins in Liquids. 



stem (Fig. 2, C 1), on the edges of which a backward rotation is im- 

 mediately manifested, an evident sign of the resistance and friction of 

 the ambient mass. Hardly is the drop detached from the tube before 

 we see it widening on its stem and becoming hollow below (Fig. 2, 

 C 2) ; the edges fold back and soon take the motion of a winding 

 scroll, which seems to attract to itself the lingering part of the colored 

 filament (Fig. 2, C 3). Once begun, this whirling motion is continually 

 kept up by the friction, which, upon the exterior contours, exhausts a 

 little of the acquired velocity. The whole substance of the drop will 

 pass into it, and with it numerous molecules of the uncolored liquid, 

 the interposed layers of which will assist in supporting the geometrical 

 rolling up of the steadily growing spirals. It is really an endless reel- 

 ing, a stretching out into a surface of the whole of a little liquid mass ; 

 so that finally (Fig. 2, C 4) the line of the front appears as only a mi- 

 nutely fine thread, which is destined to burst under the strain of the 



