Transmission of Electric Waves along Wires, 359 



ground of consistency of the separate readings. Further, 

 the experimental curves were in all cases plotted before 

 superposition of the theoretical ones. 



Experimental Arrangements. 



5. The arrangement of the apparatus adopted for observing 

 the reflected wave-trains is diagrammatically represented in 

 fig. 1. In this figure, A denotes the battery of two storage- 

 Fig-. 1.— Circuit arranged for Reflected System and for Interference 

 Phenomena. 



r, ^ 



Is 



F 



E 



D 







*7 



"H 



r 



£ 



D' 



cells, B and C are the primary and secondary coils respect- 

 ively of the induction-coil, of which C has a resistance of 

 3000 ohms and an inductance of about 20 henries. G is the 

 spark-gap, which was adjusted to 2 mm., the balls being of 

 brass, highly polished before each occasion of experimentino-. 

 The wire PGrP', measured along the semicircle, is about 

 2 metres long. PP' are the edge-views of the condenser- 

 plates of zinc 40 cm. diameter placed opposite to and 30 cm. 

 distant from the precisely similar disks S S'. 



6. The line is represented by SEDTT'D'E'S'. and consists 

 of two parallel copper wires, 1*5 mm. diam., and kept 8 cm. 

 apart by wood separators at intervals of about 1 metre. These 

 wood separators are about 12 cm. long, 2*5 cm. wide, and 

 1'2 cm. thick, and were well saturated before use in melting 

 paraffin -Wax. Their resistance was thus raised to something 

 over 60,000 megohms each, which thus renders the leakage 

 of the line quite negligible. 



7. EE' denotes the electrometer, which has a single plane 

 needle initially uncharged, and suspended by a fine quartz 

 fibre between two disks attached to the line at E and E'. 

 The needle is therefore electrified by induction whenever a 

 wave-train passes EE', and its ends are consequently attracted 

 to the disks whatever the sign of their potential -difference. 

 The first throw of the electrometer is thus proportional to 

 the time-integral of the square of the potential-difference. 

 The needle is provided with weak magnetic control and a 

 plane mirror bv Adam Hilger, its indications being read bv 



2 C 2 



