4-2 Mr. W. Swan on certain Phenomena of 



of chloroform, the same ratio as the number of particles of 

 potash in the elementary portion of the surface has to the 

 number of particles of chloroform contained by it. Now the 

 fluids are symmetrically situated in contact with the wall of 

 the vessel, and the attracting molecules are therefore similarly 

 situated on both sides ; hence whatever law of attraction exists, 

 the resultant force of all the individual attractions will in both 

 cases be simply proportional to the products of the numbers 

 of the mutually attracting molecules. But this product is 

 evidently the same in both cases; hence the resultant attrac- 

 tions of both liquids upon their mutual surface will also beequal. 

 This perhaps may be rendered more evident by the following 

 considerations. Let r represent the ratio of the number of 

 attracting molecules in a given volume of solution of potash to 

 that of the attracting molecules in an equal volume of chloro- 

 form. Then, since the sphere of sensible attraction evidently 

 extends to the same distance in both liquids, we may suppose 

 it in both to be divided into an equal number of corresponding 

 thin concentric spherical surfaces. If n be the number of 

 attracting molecules in one of these attracting spherical layers 

 of chloroform, rn will be the number in the corresponding 

 layer of solution of potash; and, on the other hand, if n' be 

 the number of molecules of chloroform in the small element 

 of the mutual surface of the liquids, rn' will be the number of 

 molecules of solution of potash which it contains. Now as 

 the distances of the attracting molecules in the corresponding 

 spherical layers from the attracted element of the surface is 

 the same in both liquids, the attraction of a single pair of mo- 

 lecules will be the same in both cases ; and therefore the ratio 

 of the attractions of the two spherical surfaces to the elementary 

 particle will be that of the products of the numbers of the 

 mutually attracting molecules. The one force will therefore 

 be that of m molecules of potash attracting n' molecules of 

 chloroform, and will be represented by mn' ; the other force 

 will be that of n molecules of chloroform attracting rti' mole- 

 cules of solution of potash, and will therefore be also repre- 

 sented by mn 1 . Since then the attractions of the corresponding 

 spherical layers of the liquids upon the elementary particle of 

 the surface are equal, the whole attractions on either side will 

 also be equal. 



The resultants of those attractions will then evidently be two 

 equal forces, inclined at an angle of 45° to the mutual surface 

 of the liquid at the point of its junction with the wall of the 

 containing vessel ; and these again will have for their resultant 

 a single horizontal force perpendicular to the wall of the vessel, 

 and therefore tending directly to counteract its attraction for 



