80 Intelligence and Miscellaneous Articles. 



become as small as possible. The force aj^, which is at work in 

 the common boundary of the liquids 1 and 2, has been called the 

 surface-tension. Eighteen years ago I described several methods 

 of determining it*. 



Analogous forces must be assumed to exist at the boundary of a 

 solid with air, or with another liquid. These surfaces also have 

 the tendency. The phenomena at the boundary of a liquid and of 

 a solid are essentially different from those at the boundary of two 

 liquids, for in the former there is no lateral displacement of the 

 particles of the solid. 



While the boundary of two liquids forms spheres or spherical 

 shells, if we disregard the action of gravity, the boundary of a liquid 

 and of a solid forms folds, and under certain conditions cylindrical 

 forms, or tubes. 



I obtained thin solid laminae by allowing albumen or aqueous 

 solutions of glue, or alcoholic solutions of resins, to dry on mercury 

 the surface of which had been covered with a trace of fat. 



The periphery of the solid lamina forms thus a sine curve, which 

 lies upon a vertical cylinder surface, and is connected with the 

 centre of the lamina by radial straight lines. The periphery of the 

 solid lamina is then alternately higher and lower than the original 

 horizontal surface of mercury. 



On the periphery there can be n elevations and n depressions, 

 where n is any whole number 1, 2, 3, 20, 100, or more. 



The thinner the lamina and the greater its diameter, the greater 

 in general is n, and the smaller the vertical height of the elevations 

 and depressions. 



The edge of the solid lamina may also be periodic in several 

 ways. Thus, for instance, there can be simultaneously two or 

 three great folds, and twenty-four or still more small folds at the 

 periphery. 



The magnitude and shape of the solid lamina depends on the 

 surface-tension of the fatty surface of mercury, that is to say, on 

 the thickness of the fatty layer on mercury, on the temperature, 

 and on the radiation, so that heliotropism can be discovered on it. 



Solid lamiuse, the thickness of which is less than 0*000045 

 millim., may modify the form of the surface and exhibit a folded 

 surface. The thickness may be so small that it can no longer be 

 perceived with the microscope. 



If flat air-bubbles in water or flat drops of mercury in air are 

 coated with very thin solid laminge, the form of the bubbles and 

 drops are modified in the same way as by a coating with a soHd 

 lamina. 



Thin solid laminae of glue, resins, soap, albumen, thin metal 

 layers, formed cylindrical shapes or tubes on the surface of mer- 

 cury, water, chloroform, or fatty oils, with air or with other liquids, 

 if tiie surface tended to become as small as possible, and was pre- 

 vented from assuming the spherical shape by not being able to 

 move laterally. — Berliner BericTite, July 12, 1888. 

 * Pogg. Ann. vol. cxxxix. (1870). 



