46 POPULAR LECTURES AND ADDRESSES. 



convenience it is shown, as in the enlarged draw- 

 ing of the nozzle (Fig. 30), exactly hemispherical. 

 By means of the siphon the difference of levels, 

 h, between the free-level-surface of the water in 

 the vessel to which the nozzle is attached, and the 

 lowest point in the drop hanging from the nozzle, 



-Jr. 



FIG. 30. 



may be varied and corresponding measurements 

 taken of k, and of r, the radius of curvature of the 

 drop at its lowest point. This measurement of 

 the curvature of the drop is easily made with 

 somewhat close accuracy, by known microscopic 

 methods The surface tension, T, of the liquid is 



