170 



Proceedings. 



fluids. If the surface of the vessel were flexible, the motion 

 of the fluids would be essentially that of a particular 

 portion of the water in a long wave adjacent to the surface 



as shown in the figure. In this, the plain lines indicate lines 

 in the water at rest, which take the position of the dotted 

 lines when the wave surface has the position of the thick 

 dotted line. The black circle indicates the surface of the 

 spherical vessel ; and the dotted curve shows the shape this 

 surface would become if it were subject to the same distor- 

 tion as the water. In fact, the vessel is rigid, and the 

 surface of the water must conform to it, which requires 

 further internal distortional motion of the water. It is 

 seen there is an excess of water at the top on the higher 

 side and a deficiency on the lower, to supply which the 

 upper surface must be still further tipped, while there is a 

 deficiency on the higher side below and an excess on the 

 lower side, to remedy which the lower surface must tip in 

 the opposite direction. This is exactly what is seen with 

 the oil and water, and is there though it cannot be seen in 

 the water, although not to so great an extent because 

 there is no possibility of an internal wave as between the oil 

 and water." 



