Trowbridge — Electric Discharges through Hydrogen. 3i3 



the circuit is silent ; moreover, a large self-induction included 

 in the circuit does not affect the striae. 



Under certain conditions the current from a storage battery 

 oscillates, or pulsates, but such oscillations or pulsations do not 

 seem to modify the appearance of the stratifications. If, on 



c 



Fig. 3. 



) 



Fig. 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, nnder the 

 motion of the pistons, undulates in waves which can be studied by instanta- 

 neous photography. P and P' are the pistons, and D is a diaphragm w T ith a 

 rectangular orifice. 



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 hydrodynarnical analogy is afforded by 

 the motion of two pistons moving against each other at differ- 

 ent rates in a channel filled with water. 



Fig. 4. 



Fig. 4 represents a case in which P moves twice as fast as P'. The waves 

 are formed nearer the slower-moving piston. The method seems to be use- 

 ful in studying ripples and waves. 



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 with reference to striae ; 

 but one who was ignorant of this theory, seeing the action 

 of the cathode in driving back striae into the anode, might 

 attribute this action to an actual repelling force, arising from 

 the cathode. When this supposititious force is diverted by a 

 magnet the striae appear and more current flows. One igno- 

 rant of the many facts of ionization by collision might further 

 suppose that heavier particles of slower motion might be held 

 back by swifter particles issuing from the cathode. These 



