the Adhesion of Liquids to Liquids. 403 



globules are shot out from it in radial lines ; the figure sails about 

 over the surface of the water, diminishing in size, and vibrating 

 even more rapidly, until at length it disappears. (See Plate IV. 



I have already explained* that this figure is the resultant of 

 two forces — namely, that of cohesion among the particles of the 

 creosote, which tends to keep the figure together, and that of 

 adhesion of the surface of the water, which tends to break it up. 



The figure from one drop of creosote on the surface of two 

 ounces of distilled water contained in a shallow glass vessel 3 

 inches in diameter lasts about five minutes. But if the tempe- 

 rature be below about 50°, the cohesion of the figure cannot re- 

 sist the adhesion of the surface. As soon as the drop is placed 

 on the water, the figure is formed for an instant, but it splits 

 open, forms a kind of brittle arc (figs. 2 & 3), which is shivered 

 into a number of separate disks (fig. 4), each of which is a per- 

 fect cohesion-figure of creosote. These figures perform their 

 evolutions independently of each other, sailing about with rapi- 

 dity, but never clashing with or disturbing each other f. 



The drop of creosote, instead of forming an active figure, may, 

 under certain conditions, rest on the surface of the water in the 

 form of a well-shaped double-convex lens. These conditions are, 

 (1) want of adhesion, which may result from impurity of surface, 

 and is to be got rid of by a thorough washing; or (2) that un- 

 explained condition of inactivity already referred to. This inac- 

 tivity can be produced by heat. For example, the end of the 

 glass rod used for depositing the drop on the water was held in 

 the flame of a spirit lamp for a short, time and then dipped into 

 the creosote. The drop delivered to the surface of the water 

 was an inactive lens. After about two minutes it became active. 

 The rod. was kept in boiling water for some minutes, and after 

 a hasty wiping was used for depositing the drop ; an inactive 

 lens was again formed. A few drops of etLer were poured on 

 the surface of the water and fired ; the surface was rendered in- 

 active for about five minutes ; the drop of creosote then flattened 

 down from a lens into a disk with a sharp edge ; it began to 

 sway about, then to progress slowly over the surface ; in five 

 minutes more the edge began to quiver, and, after various at- 

 tempts, the vibratory motion set in, but not with the vigour dis- 

 played by the figure under its most favourable conditions. It 



* Phil. Mag. August and October 1861. 



t In the following experiments (unless otherwise stated) the same vessel 

 of 3 inches in diameter was used with 2 oz. of distilled water. The vessel 

 was cleaned after every experiment, either with sulphuric acid or caustic 

 potash solution. Morson's creosote, redistilled at about 418% was used. 

 The distillate was bright and colourless, and did not become coloured by- 

 exposure to light. 



2D2 



