4 (J. A. Chant — Variation of Potential along the 



hard-rubber plate, p, by wax, and the detector was then hung 

 on the stretched wire at any place desired. 



The curves are plotted from the mean of at least three sets 

 of readings. 



The published accounts of the exploration of wires about 

 which electrical disturbances are produced as in wireless tele- 

 graphy are not numerous, and, as far as I can learn, in no case 

 has the exploration been at all minute. 



In the present investigation three methods, well-known in 

 practice, have been used to excite the oscillations. 



Marconi'' s Simple Method. 



This arrangement is illustrated in tig. 2. The " oscillator " 



in this case consisted of two cylindrical brass rods, AB, CD, 



9.5mm j n di am eter and 12*5 cms long, ending in spherical knobs 



B, C, 3'8 cm in diameter. One half of the doublet is shown on 



is 



T 



■t+ 1 * 



Tj D . 



a larger scale at the left-hand of fig. 2. From D led off the 

 antenna DE. In some experiments A was connected to earth, 

 in others a wire similar to DE was attached to A, while in one 

 series this end of the doublet was left entirely free 



The knobs B, C were not kept polished, and the spark was 

 about l*9 mm long. 



For earth, in the case of wires of lengths 500, 1500 and 

 2000 cms , A was joined immediately to a large sheet -of tin, 

 which, along with about two square meters more of sheet metal, 

 was firmly connected to a steam-heating radiator near by. For 

 the wire 1000 cms in length the connection from A to the sheet of 

 tin was about 75 cms long. 



The wire joined to A in place of the earth connection was 

 precisely the same as that acting as antenna and attached to D ; 

 and in order to prevent inductive effects between these two 

 wires the former was. drawn up in a vertical direction by a 

 cord over a pulley in the ceiling. 



The readings were taken at points, usually 20 cms apart, from 

 one end of the antenna to the other, the order of the readings 

 in some cases beginning at the free end, in the rest moving 

 towards it. 



