132 future's rtMractes. 



ing railroad-train with the head office at the 

 end of the line. In this case the message was 

 transmitted a part of the distance through the 

 air; another instance of wireless telegraphy. 

 The operation was as follows: One of the 

 wires strung on the poles nearest to the track 

 was fitted up with a vibrator and key at the 

 end of the line similar to that of the Way du- 

 plex just described. In one of the cars was 

 another battery, key and vibrator, and as only 

 one tone was used, no tone-selecting device or 

 harmonic relay was needed, but instead an or- 

 dinary receiving-telephone was used to read 

 the long and short sounds sent over the lines. 

 One end of the battery in the car was con- 

 nected through the wheels to the earth, while 

 the other end was connected to the metal roof 

 of the car. Being thus equipped, we will sup- 

 pose our train to be out on the road forty or 

 fifty miles from either end, of the line, moving 

 at the rate of forty miles an hour. The opera- 

 tor at Chicago, say, wishes to send a mos-auc 

 to the moving train; he operates his key in 

 the ordinary manner, which makes the current 

 on the line vibratory during the time the key 

 is depressed. These electrical vibrations cause 

 magnetic vibrations, or ether-waves, to radiate 

 in every direction from the wire, at right 

 angles to the direction of the current, like rays 

 of light. When they strike the roof of the 

 car they create electrical impulses in the metal 



