Liquids on the Surface of Water. 33 



d. If about seven or eight parts of water be shaken up with 

 one part of ether, the experiments a, b, c can no longer be per- 

 formed on the surface of the resulting solution ; but if this so- 

 lution be boiled and filtered and left till cold, the results «, b, c 

 can be obtained on its surface as before. 



2. Experiments of this kind were performed by means of the 

 vapours of various volatile bodies ; but a very remarkable dif- 

 ference appeared in the behaviour of the vapour, according, as it 

 seemed to me, as it had a strong attraction for the water, or for 

 the substance of the film. In the one case the vapour would thin 

 out and even disperse the film ; in the other it would gather it 

 up, thicken it, and deprive it of colour. For example : — 



e. The ether-sponge was held over a film of oil of lavender ; 

 the latter was scattered and dispersed. A sponge dipped in 

 benzole was now held over the surface, when the parts of the 

 film became gathered together and thickened. In like manner, 

 a film of oil of peppermint was scattered and dispersed by ether- 

 vapour ; but when the turpentine-sponge was held over the sur- 

 face, the scattered parts sailed up to it and, being thus gathered 

 together, formed a number of thickening lenticules. Other ex- 

 amples of this action will be given hereafter (18). 



/. A drop of creosote on the surface of water will sometimes 

 split up into a number of separate lenticular masses, sometimes 

 remain as one such mass — each lens having motions of vibra- 

 tion and translation, and so wasting away. 



3. Now in such a case as this (/), as the water approached 

 the limit of saturation, the motions of the creosote became 

 slower, and ceased altogether when saturation was fully attained, 

 just as, in the case of the ether repulsions, the experiments a, b, c 

 could not be performed on a saturated solution (as in d) . 



4. Hence these effects seem to arise out of that kind of ad- 

 hesion which, overcoming cohesion, constitutes solution, and, 

 when the two forces are in equilibrium, saturation. The strong 

 attraction or adhesion of water for ether- vapour, and the appear- 

 ance of the latter on the surface as a disk of liquid ether, combined 

 with the expansive force and weight of the ether-vapour, appa- 

 rently explained such results as those given under a, b, c ; while 

 the motions of the creosote (/) seemed evidently to come under 

 the phenomena of solution. When, for example, a quantity of 

 water had been saturated with creosote, so that all further mo- 

 tion was suspended, since solution was complete, if the quantity 

 of water w r ere increased, the motions set in again, and that with- 

 out increasing the superficial area of the water ; so also if the 

 solvent power of the water was increased, as by the addition of 

 a drop of acetic acid, the motions of the creosote were renewed. 



Phil Mag. S. 4. Vol. 39. No. 258. Jan. 1870. D 



