AND FORMS OF LIQUID FILMS. 117 



having the plane film in its centre, sometimes vertical, sometimes horizontal), 

 may be produced by simply dipping the vessel in the solution and raising it with 

 M N closed ; but these systems can all be obtained with much greater ease and 

 certainty by blowing small bubbles within the vessel in the same way as was 

 done with the single cone. Figs. 11 to 14 exhibit these systems respectively. 

 The system formed by thus inserting two bubbles of equal .size is shown in 

 fig. 11 ; that by inserting three such, in fig. 12 ; that by inserting four, in fig. 13. 

 This last system is, like that formed within the single cone, united in its centre 

 by a plane quadrilateral film, which, as in the experiment with the single cone, 

 may be obtained in the horizontal instead of in the vertical position, by introducing 

 a plane film at or near CD, before inserting the bubbles, vide fig. 14. All the 

 preceding experiments with single and double cones may be performed with 

 cones of any angle, the forms of the curvatures of the figures produced being 

 modified accordingly. 



These experiments may likewise be further varified by using cylindrical tubes 

 instead of cones. If a system of three bubbles be adopted, a small bubble inserted 

 in their centre will take the form of a triangular prism ;* with four, a cube ; with 

 five, a pentagonal prism ; with six, a parallelopiped, and so on ; or two cubes, 

 two parallelopipeds, &c, may be inserted one above the other, forming systems 

 analogous to that in Plate xxxiv. Fig. 5, of vol. xxiv. of " The Transactions." 

 If two cubes be thus inserted into the system formed in the single cone, and the 

 system be then allowed to rise in the cone, the lower cube will retain more or 

 less its quadrilateral form, while the upper passes into the pyramid — a state of 

 things which may be compared to that previously described with the wire 

 pyramid, and shown in Plate xxxiv. Fig. 11, of vol. xxiv. of "The Transactions." 



When a cylinder is used, the vertical lines of the prism, cube, &c. thus intro- 

 duced are straight lines, their horizontal lines being outwardly convex. 



IV. On some Miscellaneous Experiments on Paraboidal, Conical, and Cylindrical Films. 



If the cone previously described be dipped in the solution, so that it is filled 

 to A B, and MN be then closed, we obtain, on raising the cone, a paraboidal film 

 at CD, and a plane film about half way up the cone (fig. 15). The paraboloid, 

 as the excess of fluid escapes from its apex, becomes first a hemisphere, then the 

 segment of a sphere, and then bursts. 



If two very convex films be placed in contact with one another, they will 

 become united by a more or less flattened film, which, as already shown in the 

 previous paper on this subject (Vol. xxiv. p. 503, of the " Transactions"), will be 

 plane, convex, or concave, according to the relative convexity of the bubbles 



* This figure is best obtained by inserting the small bubble before inserting the third of the 

 large bubbles. 



