86 Mr. E. H. Barton. Electrical Interference [June 15, 



3. Following the researches of these physicists, and in the same 

 laboratory,* I have endeavoured to trace, both theoretically and 

 experimentally, the relation between the length of this abnormal 

 part of the " secondary " and the relative intensities of the 'trans- 

 mitted and reflected disturbances into which the original incident 

 wave is thereby divided. 



4. The following diagram and accompanying descriptive notes will 

 sufficiently explain the apparatus used in the experiments : 



Fm 1. Diagrammatic Outline of the Apparatus used for producing and measuring 

 the Interference of Electrical Oscillations. 



EXPLANATION OF FIG-. 1. 



I. Induction coil worked by two secondary cells. 



G-. Spark gap (usually 2 mm.). 



PGP 7 . (Measured along the wires) is 204 cm., the wires PG-, GrP' are 2 mm. dia- 

 meter. 



PP'. Condenser plates of zinc 40 cm. diam. to form the ends of the Hertzian 

 primary oscillator. 



SS'. Similar plates at a distance of 30 cm. from P and P', and forming the beginning 

 of the " long secondary," which consists of copper wires 1 mm. diameter. 



Distance AA' = BB' = CO' = DD' = 8 cm. 



BC B'C'. The abnormal part of the long secondary used to produce the reflection 

 and interference phenomena. 



EE'. Electrometer.! The needle is uncharged : it therefore turns in the same 

 direction whenever there is any potential difference between E and E 7 , what- 

 ever the sign of that difference. 



DD'. Wire bridge across the main wires. 



Length AD = A'D' = 160 m. nearly. ED = i\ 2 where ^ denotes the ware-length 

 in the long secondary. 



* Namely, in the University of Bonn, under the guidance of Professor Hertz. 



"t" Herr von G-eitler kindly left for my use the instrument made by him and 

 described in ' Wiedemann's Annalen,' vol. 49, p. 188. I am also indebted to him 

 for full verbal explanations of his researches prior to their publication, and hereby 

 tender him my hearty thanks. 



