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XLII. On certain curious Motions observable at the Surfaces of 

 Wine and other Alcoholic Liquors. By James Thomson, 

 A.M., C.E., Belfast*. 



THE phfenomena of capillary attraction in liquids are ac- 

 counted for^ according to the generally received theory of 

 Dr. Youngj by the existence of forces equivalent to a tension of 

 the surface of the liquid, uniform in all directions, and indepen- 

 dent of the form of the surface. The tensile force is not the 

 same in different liquids. Thus it is found to be much less in 

 alcohol than in water. This fact affords an explanation of several 

 very curious motions observable, under various circumstances, at 

 the surfaces of alcoholic liquors. One part of these phsenomena 

 is, that if, in the middle of the surface of a glass of water, a 

 small quantity of alcohol or strong spirituous liquor be gently 

 introduced, a rapid rushing of the surface is found to occur out- 

 wards from the place where the spirit is introduced. It is made 

 more apparent if fine powder be dusted on the surface of the 

 water. Another part of the phsenomena is, that if the sides of 

 the vessel be wet with water above the general level surface of 

 the water, aud if the spirit be introduced in sufficient quantity 

 in the middle of the vessel, or if it be introduced near the side, 

 the fluid is even seen to ascend the inside of the glass until it 

 accumulates in some places to such an extent, that its weight 

 preponderates and it falls down again. The manner in which I 

 explain these two parts of the phsenomena is, that the more 

 watery portions of the entire surface, having more tension than 

 those which are more alcoholic, drag the latter briskly away, 

 sometimes even so as to form a horizontal ring of liquid high up 

 round the interior of the vessel, and thicker than that by which 

 the interior of the vessel was wet. Then the tendency is for the 

 various parts of this ring or line to run together to those parts 

 which happen to be most watery, and so there is no stable equi- 

 librium, for the parts to which the various portions of the liquid 

 aggregate themselves soon become too heavy to be sustained, 

 and so they fall down. 



The same mode of explanation, when carried a step further, 

 shows the reason of the curious motions commonly observed in 

 the film of wine adhering to the inside of a wine-glass, when the 

 glass, having been partially filled with wine, has been shaken so 

 as to wet the inside above the general level of the surface of the 

 liquid ; for, to explain these motions, it is only necessary further 

 to bring under consideration that the thin film adhering to the 



* Communicated by the Author, having been read at the Meeting of the 

 British Association at Glasgow. 



