as Radiators in Wireless Telegraphy. 685 



The transmitter coil, in series with a suitable condenser, 

 was connected by the long parallel wires or tails with a 

 Poulsen arc in the adjacent electrical laboratory, and per- 

 sistent oscillations excited in it. The similar receiver circuit 



at a distance had a condenser of equal capacity in series with 

 it and a variable inductance for tuning. The oscillation valve 

 had its terminals connected to the receiver circuit condenser- 

 plates and wires taken from it to a mirror galvanometer 

 placed in a distant room. The transmitter coil had then 

 persistent oscillations set up in it by the arc, and the trans- 

 mitter and receiver coils were placed at various distances and 

 in various relative positions, and the current created in the 

 received circuit was in each case measured by the galvano- 

 meter and valve. 



When either of the square coils were placed with their 

 planes normal to the line joining their centres and vertical 

 to the earth surface, we shall call this position A. When 

 either of them were placed with plane parallel to the line 

 joining their centres and vertical to the earth we shall call 

 the position B, and when they were placed with plane parallel 

 to the surface of the earth we shall call this position Q. 

 Thus if we represent the coils as seen in plan or looking 

 down on them from above we can denote these positions as 

 follows : — 



A 



B 



C 



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