n. 



ELECTRICAL WAVES IN LONG PARALLEL WIRES. 

 By A. D. Cole. 



Read before the Am. Assoc, for the AdiJancement of Science, at Buffalo, Aug. 1896. 



The experimental study to be described in this paper was under- 

 taken as a preliminary to a research on the refractive index of certain 

 liquids for electrical undulations as deduced from a measurement of 

 the ratio of wave-length in the material under investigation to that in 

 air. That research has been published in Wiedemann^ s Amialen ( Feb- 

 ruary, 1896) and in full abstract in the July number of the Physical 

 Review, but so many facts not hitherto described were noted in the 

 prehminary study that I have ventured to bring them before you in the 

 present paper. 



Stationary electrical waves were produced in two long wires ac- 

 cording to Lecher's modifications of the original method of Hertz. 

 The apparatus used is shown in Fig. i. 



/ is an induction coil capable of giving a spark several centimeters 

 long. Wires from its secondary terminals are joined to the two pri- 

 mary plates P P' , the latter being connected (except for a spark gap 

 2 to 4 mm long ) by short rods terminated by brass balls. 



The distance between the primary plates could be varied by slid- 

 ing these rods in their support, and the resulting changes in the capac- 

 ity and self-induction of the system controlled the oscillation period. 

 The primary plates were 40 cm. square and from 3 to 10 cm. apart. 

 From the oscillations set up in these by the discharges of the induction 

 coil, oscillations were induced in two secondary plates, s s' , each 10 cm. 

 square, placed a few centimeters in front of the primary plates. To 

 the centre of each secondary plate a long wire was attached and these 

 two wires, after approaching ( as seen at a a' ) to a distance of 8 cm. 

 apart, stretched away horizontally and parallel a distance of about 4 

 meters. At every oscillation of the secondary plates a wave of elec- 

 tricity passed along each wire, was reflected back at its end and pro- 

 duced, by interference with new advancing waves, a system of station- 

 ary waves with alternating nodes and ventral segments, analogous to 



