On certain Phenomena of Capillary Attraction, 37 



the presence of the Canada balsam, for which the chloroform 

 manifests a strong affinity, and which it dissolves rapidly. I 

 have since observed the surface of the chloroform in a tube, 

 having plates of glass held in contact with its ends by means 

 of vulcanized India-rubber bands. In this case the eye was 

 assisted by a lens magnifying about eight times, and the sur- 

 face of the chloroform was again seen to be slightly depressed 

 at its contact with the tube ; but as the plates were attached 

 without cement, there was no reversal of the surface of the 

 chloroform at their junction with the tube. From these ex- 

 periments it would seem that the effect of the alkali is not so 

 much to alter the form of the curved surface, as to produce a 

 curve on a smaller scale, and thus to diminish the distance to 

 which the curvature extends from the sides of the vessel : so 

 that a deep depression at the sides is so much reduced as only 

 to be perceptible by minute inspection ; and consequently the 

 curvature, which formerly extended to a distance over the 

 liquid, is now confined to such narrow limits as to leave the 

 greater part of the surface sensibly flat. 



As potash has a chemical affinity for chloroform which is 

 not possessed by hydrochloric acid, it occurred to me to try 

 whether, in other cases besides those observed by Dr. Wilson, 

 a flat surface would be formed by liquids having a strong affi- 

 nity for each other, and a curved surface by liquids having a 

 feeble affinity. 



The following are the principal results I have obtained : — 



1. Olive oilfloatingon the surface of water orof hydrochloric 

 acid, has its under surface convex, but with solution of potash 

 its surface is apparently flat. It has also, in contact with 

 alcohol or sulphuric aether, a much flatter surface than with 

 water. 



2. Spermaceti oil also exhibits a convex surface in contact 

 with water and hydrochloric acid, and a flat surface with solu- 

 tion of potash. 



3. Oil of cloves sinks in water, and has a highly convex 

 surface, which becomes nearly flat on the addition of alcohol 

 to the water; but the liquids mingle so readily, that their 

 mutual surface is not very well defined. 



4. Oil of cassia sinks in water; and its surface, which is 

 very convex, is considerably flattened by adding potash or 

 alcohol to the water. The addition of acid in the former case, 

 or of water in the latter, restores the convexity of the surface. 



5. Oil of lavender floats on water, with its under surface 

 convex. If alcohol is poured upon it, its upper surface is 

 nearly flat. 



In all the instances now enumerated, as well as in those 



