Page:Popular Science Monthly Volume 36.djvu/642

624 films to those made with soap-suds and glyceric fluid. We have reversed the order in considering them, but it amounts to the same thing in the end.

Plateau's researches have been carried on by Brewster and others, and the subject much enriched by later experimenters. One of the most beautiful forms has not, it is believed, been published. A sphere is outlined with three equal circles, making, when joined together at equal angles, a globe with six meridians. When this is dipped in the suds, a rather complicated figure appears. It is sometimes necessary to dip this frame several times to get a perfect figure. From an axial edge of film three films start out. Just half-way between the axis and the outside curve of the sphere each of these three films meet two crescent-shaped films from two of the wire meridians, curved so that the three meet at the required angle. Sometimes when a bubble has been caught in the system, and always if a small bubble is carefully blown between two of the wires, a new figure will be formed. In an instant, as though the change were wrought by magic, the new figure flashes into existence. A long, six-sided, melon-shaped figure reaches from pole to pole inside the sphere; from each edge of this figure, entirely unsupported as it is by the wire, a crescent-shaped film reaches to each wire meridian.

The figures formed with the wire frames are usually perfectly symmetrical; but sometimes, from the peculiar form of the frame, symmetry is not consistent with a union at the angle of 120°. The law in such a case is obeyed, and symmetry cast to the winds. In Fig. 6, at the first dip the figure is very unsymmetrical, though always the same. When a bubble is blown on the bottom, the figure starts out perfectly symmetrical in form.

Brewster has added many experiments to those of Plateau's. The next one given is his, and a very curious one it is too. Two rectangles are made of the copper wire; one is slipped within the other and held at right angles to it; they are in this position dipped into the suds. The system which starts into being can be seen in Fig. 7. The central oval stands diagonally just half-way between two of the angles made by the crossed frames. Now, if the frames are gradually turned upon each other, which it is very