No. 453-] ACTIVITIES OF AM aiBA. 629 



the mercury moves and changes form in a strikin,-;- manner, 

 sending out projections or becoming wholly irregular, at the 

 same time moving from place to place. ^ 



The present author (:02) has given another tiiethod of 

 observing such movements. A mixture of three ])arts glycerine 

 and one part 95 "jo alcohol is placed on a slide and eoveied with 

 a large cover-glass, supported near its ends by glass lods. Be- 

 neath the cover-glass a drop of clove oil is introdiu ed l)y means 

 of a medicine dropper drawn to a fine point. The akohol acts 

 locally on the surface of the clove oil, decreasing its surface ten- 

 sion here and there. As a result the clove oil drop changes 

 form, sends out projections and moves from place in a strik- 

 ing manner. The phenomena shown are similar to those in 

 Butschli's drops of oil emulsion. The experiments are much 

 easier to perform than those of Biitschli ; by varying slightly 

 the amount of alcohol in the mi.xture one can always be certain 

 of getting marked results. But the movements do not continue 

 so long as in Butschli's experiments. 



In all these experiments the movements are due to local 

 changes in surface tension. When such a local change is pro- 

 duced on the surface of a fluid drop a characteristic set of cur- 

 rents results. From the region of least tension surface cur- 



