46 Mr. C. Tomlinson on the Motions of certain 



air capable of producing evaporation be introduced, the liquid 

 film creeps up the interior with thick or viscid-looking pendent 

 streams descending from it like a fringe from a curtain ; the 

 more watery portion draws itself away from the more alcoholic 

 portion, as when a drop of alcohol is put into the centre of a 

 thin stratum of water the water will retire (10), (28). 



29. If the conditions be inverted and a drop of water be de- 

 posited on a thin stratum of ether or absolute alcohol, the drop 

 assumes the form of a well-defined spherical segment, notwith- 

 standing the great affinity existing between the two liquids. So 

 also a stratum of olive-oil retreats before a drop of turpentine, 

 cold water before hot, distilled water before soapy water, and 

 so on. Invert these conditions, and there is no retreat of the 

 liquid. 



30. The phenomenon pointed out by M. Jeit teles in 1853 20 

 belongs to differences in surface-tension. When a liquid de- 

 scends in a thin layer down the interior surface of a funnel or of 

 the vessel which receives it, light particles floating on the sur- 

 face rise sometimes many centimetres in a direction contrary to 

 that of the current and describe within this current oval lines. 

 The effect may be observed with water, saline and acid solutions, 

 &c, but not with alcohol or ether. The conditions required for 

 the exhibition of the phenomenon are a liquid of great surface- 

 tension and an unclean vessel, or one more or less contaminated 

 with greasy matter, as from the hands or an ordinary glass-cloth. 

 Then, if a liquid with its surface-tension undiminished descend 

 in a layer down the side of the funnel and come into contact 

 with another portion of liquid whose tension has been diminished 

 by contact with the greasy film, this portion will tend to obey 

 the preponderating contractile force — that is to say, to form an 

 ascending current. The current is not visible unless the beak 

 of the funnel dip into the liquid in the vessel below ; and the 

 slower the motion the better the effect, since in such case the 

 effects of the higher tension are less interfered with. That this 

 explanation is the true one was proved by Professor Van der 

 Mensbrugghe, who employed a chemically clean funnel, when 

 the effect was no longer obtainable. 



31. The various motions of different liquids on the surface of 

 water which I have described from time to time, such as those 

 of creosote 21 , eugenic acid 22 , and the displacing-power of some 

 liquids over others 23 receive their proper solution in this prin- 

 ciple of surface-tension 24 . While preparing the last-named 



20 Zeitschrift fur Naturwiss. p. 445. 

 "^ See note 2. 



22 Phil. Mag.' July 1864. 23 Ibid. June 1867- 



24 There are some curious experiments described by M. Dardenne (Bull, de 

 la Soc. Roy.Botan. de Bruxelles,vo\.\\\. Nos. 1 and 2). Happening to touch 



