1882.] 



On Liquid Jets. 



139 



the large tube consists of a carefully worked plate in which is a 

 circular hole of \ inch diameter. When the rubber tube is placed in 

 connexion with the water supply, a jet drops from A, and may be 

 made exceedingly fine by regnlaton of the pinch-cock C. By turning 

 off the supply at C altogether, the jet at A may be stopped, without 

 emptying the vessel. The stability, due to the capillary tension of 

 the surface at A, preponderates over the instability due to gravity. 

 By this device it is possible to obtain a jet whose velocity is acquired 

 almost wholly after leaving the vessel from which it issues. In this 

 form of the experiment, however, the jet is liable to disturbance 

 depending upon the original velocity of the fluid as it passes through 

 the comparatively narrow rubber tube, and when I attempted a 

 remedy by suspending a closed reservoir (fig. 2), in which the water 



might be allowed first to come to rest, other difficulties presented 

 themselves. The air confined over the surface of the water acts as a 

 spring, and the flow of water below tends to become intermittent, 

 when rendered sufficiently slow by limiting the admission of air. A 

 definite cycle is often established, air flowing in and water flowing 

 out alternatively at the lower aperture. The difficulty may be over- 

 come by careful manipulation, but there is no easy means of making 

 an adequate comparison with other jets, so that the question remains 

 undecided whether the residual disturbances are principally of in- 

 ternal or of external origin. 



Collision of two Resolved Streams. 



§4. In the case of a simple vertical fountain, when the scattering is 

 prevented by electricity, there is every reason to believe that the 

 action is differential, depending on a difference of potentials of 

 colliding drops. The principal electrification, however, of the 

 successive drops must be the same ; and thus, sensitive as it is, this 



