508 Intelligence and Miscellaneous Articles. 



ON THE ACTION OF OILS ON THE MOTIONS OF CAMPHOR ON THE 

 SURFACE OF WATER. BY CHARLES TOMLINSON, F.R.S. 



In Lord Kayleigh'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 oxidized 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 completely 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 propose to apply the term catharized to 

 bodies thus made chemically clean, from Kadapos, " 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." — Proceedings of the Royal Society , 

 No. 294, September 20, 1890. 



