TROWBRIDGE. 



DISCHARGES OF ELECTRICITY. 



457 



of the stripe leads one to ask if this regularity could arise from some pul- 

 sation or rhythmical action, — the ionization being, so to speak, on top 

 of such a rhythmical action. When the striae are excited by a storage 

 battery, they are perfectly steady, and when one is sure that there are 

 no breaks in the circuit, a telephone introduced into the circuit is 

 silent ; moreover, self-induction included in the circuit does not affect 

 the stria'. 



Under certain conditions /" 

 the current from a storage ( 

 battery oscillates or pul- 

 sates, but such oscillations 

 or pulsations do not seem 

 to modify the appearance 

 of the stratifications. If, on 

 the other hand, there is a 

 flow from the cathode which 

 pulsates at a different rate from a supposititious flow from the anode, 

 one might expect striae, or accumulation of ionic disturbances at regular 

 intervals. An hydrodynamical analogy is afforded by the motion of 

 two pistons moving against each other at different rates in a channel 

 filled with water. 



Figure 2 represents an apparatus by means of which two pistons 

 driven in opposite directions by a motor cause waves in a trough 

 filled with water. 



Figure 3. 



= 



Figure 4. 



Figure 3 shows the arrangement, in plan, by means of which the 

 ripples are studied. M is a mercury lamp of the Cooper Hewitt form. 

 This is placed directly behind the trough containing the pistons. The 

 surface of the water, totally reflecting the light, forms a dark line which 

 under the motion of the pistons undulates in waves, which can be stud- 

 ied by instantaneous photography. P and P' are the pistons, and D is 

 a diaphragm with a rectangular orifice. Figure 4 represents a case in 

 which P moves twice as fast as P'. The waves are formed nearer the 

 slower-moving piston. 



All who have worked in the field of discharge of electricity through 

 gases must recognize the suggestiveness of the theory of ionization by 

 collision, especially in reference to striae ; but one who was ignorant 

 of this theory, in seeing the action of the cathode rays in apparently 



