258 Action of Oils on Motions of Camphor on Water. [June 19, 



V. " On the Action of Oils on the Motions of Camphor on the 

 Surface of Water." By CHARBES TOMLINSON, F.R.S. 

 Received May 26, 1890. 



In Lord Rayleigh's paper on the above subject, read before the 

 Royal Society on the 27th March last, and reported in ' Nature ' of 

 the 8th May, it is stated that a film of olive oil, in two or three cases, 

 " was incompetent to stop the camphor motions upon a surface 

 including only a few square inches." 



I have often noticed this fact as a consequence of the use of 

 chemically-clean materials. Water, contained in a shallow glass 

 vessel, 4 inches in diameter, on the surface of which camphor frag- 

 ments were active, was touched with rape oil delivered from the point 

 of a penknife. The fragments continued to rotate on that part of the 

 surface which had not been invaded by the oil film (' Phil. Mag.,' 

 November, 1873). I had previously noticed that a drop of a volatile 

 oil, free from oxidised products, could be spread over the whole 

 surface of the water, without impeding the motion of the camphor 

 fragments, which skated through and cut up the film. In the case of 

 old volatile oils, redistillation was found to be necessary (' Phil. 

 Mag.,' September, 1863). A similar effect was produced by a drop 

 of creosote (or its constituent acids) on a film of a fixed oil that com- 

 pletely covered the surface of the water. The creosote repels the oil 

 film, cuts it up in all directions, moving over the surface with great 

 vigour (' Phil. Mag.,' June, 1867). So also by attention to chemical 

 purity, a raft of mica carrying a bit of camphor will float about 

 briskly on the surface of water night and day during a whole week 

 and upwards ('Phil. Mag.,' December, 1869). 



By attending to the chemical purity of the materials the results 

 led to the explanation of many phenomena which had taken refuge 

 under the vague term "molecular change," or " molecular condition," 

 and to the discovery of other phenomena which had some influence in 

 developing theory. I proposed to apply the term catharised to bodies 

 thus made chemically clean, from icadapb^, " pure " or " clean " 

 ('Journal of the Chemical Society,' April, 1869; also ' Phil. Trans.' 

 for 1870). 



I may be allowed to add that, in arriving at the true theory of the 

 camphor motions and their varied kindred phenomena, Professor Van 

 der Mensbrugghe was kind enough to refer to me in his second 

 memoir, as " le physicien qui a le mieux prepare la vraie theorie de 

 ces phenomenes." 



