1893.] On Interference Phenomena in Electric Waves. 97 



last winter I made trial of an arrangement identical in principle but 

 more completely analogous to Hughes' induction balance. The 

 method seemed, however, to offer several difficulties and disadvan- 

 tages, and finally I adopted another, also, one may say, analogous to 

 Professor Thomson's, inasmuch as it measures transparencies, but in 

 outward appearance completely different from his. 



FIG. 1. 



Let ASA' be a Hertz exciter, and B, B f secondary conductors similar 

 to the primary from which a pair of long wires, stretched parallel to 

 each other, are led off for a considerable distance. One may regard 

 the wires simply as guides for the radiation, which then travels 

 straight up the space between them. If we run these wires for a cer- 

 tain length, I, through an electrolyte, the radiation will have to traverse 

 this and will be partly absorbed. If an electrometer be connected at 

 E, a quarter wave-length from the bridge at the end of the wires, 

 readings taken with various thicknesses of electrolyte should, accord- 

 ing to my expectations, give a logarithmic curve, from which the 

 specific resistance would be at once calculable. 



The actual dimensions of the exciter, &c., erected were the same as 

 those used by Bjerknes.* 



A, A', B, B' circular zinc plates, diameter 40 cm. 



Distance from A to B 30 ,, 



Length of wire ASA' (2 mm. diameter) 200 



Wave-length, X 900 



The wires B, F, D, about 1 mm. diameter, were spanned 6 cm. apart. 

 If these wires be made too short, a wave-train emitted from B, B' may 

 reach the electrolyte # l5 or the bridge D, be reflected, and return to B 

 before the primary has practically done oscillating. If this occur, the 

 state of the secondary may affect the primary as in an alternate 

 current transformer. If, however, B&! be made longer than half the 

 effective length of the wave-train, the reflected waves will not reach. 

 B until the primary oscillations have practically come to rest, and 

 under these circumstances the latter will know nothing about any 

 alternations in the secondary at or beyond x\_. This reaction of the 

 secondary on the primary had been first noticed, and to a serious 



* ' Wiedemann's Annalen,' vol. 44, p. 513, 1891. 

 VOL. LIV. H 



