Wire Transmitting Electric Waves. 57 



by a wire 70 cms long, with a spark-gap in the middle ; the 

 second, of two plates 40 cms square, joined by a wire 70 cms long 

 with a spark-gap as before ; the third had plates of the same 

 size, but the wire was 60 cms long.* 



Thus the wave-length emitted by each of these was taken to 

 be the same, namely, 560 cm3 . Now the period and wave-length 

 of the first oscillator have been found theoretically. Hertzf 

 calculates the period to be 1'26 hundred-millionths of a second 

 and the wave-length to be 4:-6 m , while Drude;f makes the latter 

 4*8 m . Both values differ considerably from that obtained by 

 resonance. Again, the second and third oscillators differ con- 

 siderably in period, though that of the second was found to be 

 the same as that of the first. (See below.) We must conclude 

 that the wave-length 5*6 m is not a very close approximation. 



In the experiments to be described presently it will be seen 

 that oscillators of the same type may differ decidedly in their 

 behavior ; that some seem able to force their vibrations upon a 

 wire, while others cannot. The wave-length of an oscillator, 

 the same as the third of the three just described, was con- 

 cluded to be 5'88 meters. 



II. Experimental Arrangement. 



While engaged during the session 1900-1, in the Jefferson 

 Physical Laboratory of Harvard University, on another investi- 

 gation! in which the magnetic detector was used, the fact that 

 an electrical disturbance about a wire parallel to the wings of 

 the detector exerted a strong action on the detector, was con- 

 tinuously and painfully evident. Indeed, the effect arising 

 from the connecting wires at first entirely masked the true 

 radiation from the oscillator. 



This suggested the possibility of conveniently exploring the 

 field along a wire by shortening the wings of the detector and 

 then placing it close to the wire at various points in its length. 

 The experiment was tried, but the demagnetization of the 

 detector was small. However, on removing one wing and 

 placing the other near the wire the effect was much greater 

 and easily measurable. 



But the action with one wing is not at all the same as with 

 two. When the detector with two wings is placed along the 

 wire, the surging in its helix and the consequent demagnetiza- 

 tion is greatest at points where the current oscillation is great- 



* Hertz, Electric Waves, Art. V, p. 81-2 ; Art. VI, p. 96-7 ; Art. VII, 

 pp. 108 and 113. 



f Hertz, 1. c.j p. 51 and p. 270 (note 6). 



X Drude, Physik des Aethers, p. 397. See also J. J. Thomson, 1. c, Arts. 289 

 and fol. 



§ C. A. Chant, An Experimental Investigation into the " Skin "-effect in 

 Electrical Oscillators, this Journal, xiii, p. 1, 1902. Phil. Mag., VI, vol. iii, 

 p. 425, 1902. 



