On certain curious Motions observable at the Surface of Wine. 331 



inside of the glass must very quickly become more watery than 

 the rest, on account of the evaporation of the alcohol contained 

 in it being more rapid than the evaporation of the water. 



That this part of the explanation is correct, or that these 

 motions of the film in the wine-glass are really due to evapora- 

 tion, may be shown by a very decisive experiment. If a vial be 

 partly filled with wine and shaken, and then allowed to rest, no 

 motion of the kind described will be found to occur in the thin 

 film wetting the inside, provided that the vial be kept corked. 

 On the cork being removed, however, and the air contained in 

 the vial, and saturated with the vapour of wine, being withdrawn 

 by a tube, so as to be replaced by fresh air capable of producing 

 evaporation, a liquid film is instantly to be seen creeping up the 

 interior of the vial with thick or viscid-looking pendent streams 

 descending from it like a fringe from a curtain. These appear- 

 ances are quite of the same kind as those met with in the open 

 wine-glass. 



Another experiment may be made to show, in a very striking 

 way, the phaeuomenon of the more watery portion of the surface 

 of a mixed liquid drawing itself away from the more alcoholic 

 portion as follows : — If water be poured to the depth of about 

 a tenth of an inch or less on a flat silver tray or marble slab, 

 previously cleaned from any film which could hinder the water 

 from thoroughly wetting its surface ; and if then a little alcohol 

 or wine be laid on the middle of that water, immediately the 

 water wiU rush away from the middle, leaving a deep hollow 

 there, and indeed leaving the tray bare of all liquid except an 

 exceedingly thin film of the spirit, which continues always thin- 

 nest close to the margin of the water, because the water di'aws 

 out to itself every portion of the spirit which approaches close 

 to its margin. 



The experiment alluded to near the commencement of the 

 present paper, in which spirit was to be introduced into the 

 middle of a surface of water previously dusted over with fine 

 powder, may be well conducted as follows : — A tube for supply- 

 ing the spirit should be provided*, which may be three or four 

 inches long, half an inch or three-quarters in diameter, and ter- 

 minating at bottom in a small open point, which, if found too 

 wide, may be partially stopped by the insertion of a piece of thick 

 soft thread, such as a strand from the wick of a spirit-lamp. A 

 knot on the thread inside of the tube will serve as a valve to cur- 

 tail or stop the flow of the spirit when required. The surface of 

 the water should be clean and free from any kind of pellicle, 



* The tube of a small glass syringe as sold by apothecaries will serve 

 the purpose well. 



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