246 Mr. C. Tomlinson on some Effects of 



if turpentine and other essential oils be newly distilled, a film of 

 any one of them on the surface of water does not arrest the mo- 

 tions of the camphor; the fragments skate through the film and 

 cut it up in all directions. Turpentine and similar oils by ex- 

 posure or long keeping become oxidized; and such products 

 of oxidation, being neither soluble nor volatile, form over the 

 surface of the water a delicate but permanent network which pre- 

 vents the adhesion of the camphor fragments. 



Creosote behaves in many respects like camphor on the sur- 

 face of water. I described its motions some years ago*; but in 

 order to observe them the surface of the water must be chemi- 

 cally clean. If not, there is no adhesion, and the drop of creo- 

 sote delivered to the surface from the end of a glass rod forms 

 an inactive double-convex lens with well-defined edges. I have 

 more recently shown f how strong is the adhesive force of creo- 

 sote for the surface of clean water, as measured by its power of 

 displacing the films of various oils, fixed as well as volatile, and 

 of resuming its activity when it has been temporarily invaded by 

 an essential-oil film. For example, a drop of castor- oil on water 

 forms a beautiful cohesion-figure; but if a drop of creosote be 

 placed by the side of it, the active creosote figure shuts up the 

 oil figure into a lens and chases it about. When the creosote 

 has disappeared, the oil flattens out into a large film covering 

 nearly the whole surface. A second drop of creosote will plough 

 through it, turning over and thickening the edges of the severed 

 portions. The creosote will in like manner repel and cut up 

 films of whale-oil, fish-oil, nut-oil, and several other fatty oils, 

 showing how superior is its adhesion to the water as compared 

 with theirs. The effects of many of the essential oils also afford 

 some remarkable illustrations of adhesion. While the creosote 

 figure is in rapid vibration, sailing about over the surface of 

 the water, if this be touched with a drop of turpentine-oil, oil 

 of cajeput, &c, the drop will flash into a film and cover the sur- 

 face, suddenly arresting the motions of the creosote. But as the 

 oil-film becomes thinner by evaporation, the creosote starts into 

 life and repels or cuts through what may be left of the oil-film. 

 When the volatile oil has disappeared, a second drop will form a 

 film that will again arrest the creosote; but as the film gets 

 thinner, the creosote begins to show twitches at the edge, and 

 suddenly it becomes active and begins to sail about. This re- 

 markable effect may be repeated a number of times on the same 

 water-surface before the creosote has entirely disappeared. 



In like manner a comparative Table of the adhesion of liquids 

 to liquids may be formed by showing what films will displace 



* Phil. Mag. for August 1861. 

 f Ibid, for June 1867- 



