IS, 



From "Fifty Years of Electricity" (The Wireless Press, Ltd.). 



A DIAGRAM SHOWING THE MANNER IN WHICH TWO RECEIVING WIRELESS 

 STATIONS EQUIPPED WITH DIRECTIONAL FRAME AERIALS CAN DETERMINE 

 THE POSITION OF AN AEROPLANE WHICH IS SENDING OUT WIRELESS SIGNALS 

 BY ITS TRAILING AERIAL WIRE A 



The frames Ci and Ca receive signals well from a station lying in the plane of the frames 

 but do not receive signals in a direction at right angles to the frame. Two such frames can 

 therefore be used to locate a station such as the aeroplane in the diagram. The planes 

 are rotated until the signals are most clear. The aeroplane must then lie in the direction 

 of each of them and therefore at their point of intersection if produced. 



FIG. i 



B 



Fig. A pictures an electrified body at rest. The 

 electric lines of force radiate out from it in straight 

 lines. In B the electrified body is in motion, and 

 the diagram represents the state of affairs an in- 

 stant after the motion has begun. The electric 

 lines of force take time to pick up the motion, as it 

 were. Thus the kink shown in the lines represents, 

 very roughly, the fact that the lines near the body 

 have taken up the motion, but that the rest of each 

 line is still lagging behind. The lines pick up the 

 motion very quickly, of course. As a matter of 

 fact the kink travels along each line at the speed of 

 light, 186,000 miles per second. 



FlG. 2. LEYDEN JAR 



This jar consists of a 

 glass bottle, coated in- 

 ternally and externally 

 with tinfoil to within a 

 moderate distance of the 

 opening. A brass rod, 

 terminated by a ball is 

 connected with the inner 

 coating and passes out 

 through the neck without 

 touching the neck. By 

 connecting together the 

 outside covering and the 

 brass ball the jar is dis- 

 charged. If, instead of 

 actually connecting to- 

 gether the two coverings 

 in this way, we bring a 

 conductor connected to 

 the outer covering to with- 

 in a little distance of the 

 ball, we shall get an oscil- 

 latory spark discharge. 

 The current will leap back- 

 wards and forwards across 

 the air-gap, in the manner 

 explained in the text, pro- 

 ducing a brilliant spark. 

 An arrangement of this 

 kind is a necessary part of 

 a wireless outfit. 



