STEADILY ALTERNATING CURRENT ON A LONG LINE. 337 



at the proper predetermined phase of minimum splash. The auto- 

 matic switch So then immediately follows, so as to keep the contact 

 closed on the line after the brushes B-^B2 have passed off the contact 

 segment. Before the brushes 8^82 close, the photographic shutter 

 is opened by the electromagnet Q, under the action of an automatic 

 switch S^. After one complete revolution of the photographic-film 

 drum, another shutter is closed by the electromagnet C2, under the 

 control of an auxiliary automatic switch ^'4. This cuts off the arc 

 light from the recording film, after about nine cycles have been 

 recorded on all three oscillographs. The whole mechanism can 

 then be arrested, by hand, at leisure. Lastly, the photographic drum 

 is removed and taken to the dark room for development. 



A photographic view of the artificial line and the oscillographic 

 apparatus is shown in Fig. 8. 



Fig. 8. Artificial Power Transmission Line, Oscillograph and Switching 



Apparatus. 



Case of Regular Transients. — About 150 different triple oscillo- 

 grams have been secured of initial electromagnetic wave transients, 

 under various conditions, over artificial lines. Only a few of these 

 can be dealt with in this paper. 



