l 7 8 



THE POPULAR SCIENCE MONTHLY 



in groups of two or three, and animated by special movements. A 

 section of the chain along its axis of revolution gives the forms rep- 

 resented in Fig. 2, A. The superposed forms of the figure, A, are 

 evidently only the successive phases of a single drop as emitted 

 at each pulsation ; and all our efforts should be directed to isolat- 

 ing the drops and retarding their descent, so as to make them 



Fig. 2. Forms op a Colored Drop penetrating a Colorless Liquid. 



more visible under their different aspects. This is easily done. A 

 variety of colored liquids are at our disposal, and, with a little alcohol, 

 or a trace of glycerine or sugar, we may modify insensibly the den- 

 sity of the liquids, reduce the action of gravity to a minimum, and 

 have at will ascending or descending currents. The last are generally 

 easiest to obtain. Fig. 3 represents a simple apparatus for the experi- 

 ment, the operation of which is dependent on the familiar principle of 

 the siphon : we have only to raise the level of the colored liquid in 

 the glass to change the rate of flow as we may wish. Certain manual 

 difficulties in handling this apparatus may be obviated by using a 

 system of communicating vessels, such as may be made by taking a 

 common lamp-chimney, corking up the lower part and putting it in 

 communication, by means of a pipe inserted in the cork and an India- 

 rubber tube, with the bottom of a similar vessel or the nozzle of a ver- 

 tical funnel. A string around the tube, or a pair of nippers, may serve 

 to regulate the flow of the colored liquid, which should be only a little 

 h sss dense than the other ; and by inclosing a bubble of air above this 

 Liquid and covering the. top of the chimney with a membrane, we may 

 vary the pressure without changing the level of the liquid. If we have 



