Proceedings of Learned Societies. 235 



PROCEEDINGS OF LEARNED SOCIETIES. 



BY W. B. TEGETMEIEE. 



ROYAL SOCIETY.— February 6. 



On the Motion of small portions of Camphor when thrown on 

 the surface of pure Water. — Mr. Tomlinson communicated a paper 

 descriptive of the very elaborate series of experiments he had made to 

 investigate this curious subject. The following is an abstract of 

 the conclusions he had deduced from his investigations : — That to 

 succeed in the production of these movements the camphor must be 

 thrown on the surface of clean water in a perfectly clean vessel. 

 That these phenomena may be also produced by certain salts, and 

 other substances that diffuse readily over the surface of water. Thus 

 the motions of camphor may be imitated by placing on water float- 

 ing rafts of talc, tinfoil, paper, etc., smeared with or containing vola- 

 tile oils, or any volatile liquid, such as ether, alcohol, chloroform, etc., 

 provided there be a communication between such liquid and the water. 

 The camphor or other volatile substance, being slightly soluble 

 in water, spreads a film over the surface of the water the moment 

 that it comes in contact with it. The dimensions and form of this 

 film evidently depend on those of the piece of camphor operated 

 on, and in general the film separates more easily from broken sur- 

 faces and angles than from a smooth surface, as the broken surface 

 of a crystal is more soluble than the natural surface. These films 

 being constantly detached from the camphor so long as it is in 

 contact with the water, displace each other, the preceding film being 

 conveyed away by the adhesion of the water in radial lines, which 

 produce motion by reaction on the fragments of camphor, causing 

 them to rotate in the same manner as a Barker's mill. These jets 

 or films of camphor can be rendered visible by various means, as by 

 fixing the camphor in water, and dusting the surface lightly with 

 lycopodium powder, when a series of currents produced by the films 

 will be made visible. The motions of the fragments of camphor 

 on water are greatly influenced and complicated by their mutual 

 attraction, and by the attraction of the sides of the vessel. The 

 film of camphor diffused over the surface of the water is very volatile, 

 disappearing as fast as it is formed, chiefly into the air, only a very 

 small portion being retained by the water. Hence camphor wastes 

 ' away much more quickly at the surface of the water than in water 

 alone, or in air alone, because at the surface the film is being con- 

 stantly formed at the expense of the camphor, and is spread out to 

 the united action of air and water. Whatever interferes with eva- 

 poration lowers or arrests the motions of the camphor and the allied 

 phenomena ; so, on the contrary, whatever promotes evaporation 

 exalts these phenomena — effects which are displayed with great 

 energy on a bright and sunny day, are produced either sluggishly 

 or not at all on a wet, dull, or foggy one. A fixed oil forming a 



