Page:Popular Science Monthly Volume 20.djvu/191

Rh 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



stem (Fig. 2, C 1), on the edges of which a backward rotation is immediately 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 reeling, 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 minutely fine thread, which is destined to burst under the strain of the