PAPER BY PROF. OBERBECK. 



147 



The greater sensitiveness of the jets for large velocities of current, 

 as also the impossibility of forming alcohol jets in water, is a direct 

 consequence from the theory of discontinuous fluid motions. Since the 

 difference of pressure in the moving and the quiet fluid is proportional 

 to the square of the velocity, therefore for greater velocities the quiet 

 liquid presses directly into the jet as soon as a slight disturbance occurs 

 in its uniform course. When Anally, with more rapid outflow, such 

 disturbances occur continually, then in general a jet can not form. 



VI. 



As already remarked above it is of interest to know the path that a 

 jet will describe when it meets a solid body iu its path. The bodies 

 used for this purpose by me were of different kinds, ami by a simple 

 arrangement were brought in the neighborhood of the discharging 

 aperture before the jet was produced by opening the stopcock. It is of 

 course understood that at the beginning of the experiment one waited a 

 long time until the movements of the liquid caused by these operations 

 had subsided. Equally also was the solid body first freed from the air 

 bubbles that adhered to it. 



The processes that occurred are most easily seen by considering the 

 following experiment. If the jet strikes upon the sharp edge of a thin 

 sheet of iron that passes parallel to the directiou of the jet and through 



its axis, then it is cut into two por 



tions which are deviated from the 



vertical directiou of the current. 



The angle between these side cur- 

 rents and the original direction of 

 (o\Tq) the jet becomes smaller little by 



little. The cause of this phenome- 

 non consists in the fact that not only 



the solid body but also the fluid 



attached thereto force the moving 



fluid into a departure to one side. 



With currents of longer duration 



on the other hand a part of the quiet 



liquid is carried along so that the two 

 upper branches of the jet slowly change their direc- 

 tion of motion and more and more nearly approach rig. 20. 

 the plane of the sheet-iron. Still one can always 

 observe quiet colorless liquid between the moving colored liquid and 

 the sheet-iron. The progress of this phenomenon depends upon the 

 original difference of pressure or correspondingly upon the velocity of 

 the flowing liquid. For a small velocity the current flows as shown in 

 Fig. 19; for greater velocities, on the other hand, the two portious of 

 the jet after a time take the position shown in Fig. 20, where the dotted 

 part of the figure is intended to show the initial direction of the current. 



