Electrical Oscillations on Iron Wires. 509 



p= ?j =3,000,000 (practically). 



Taking the cases up in order : — 



(1) Large copper wire, 



R=«285xl0 9 , 

 and substituting in Lord Rayleigh's formula 

 R' = SffifiL, 



R' = -66xl0 9 . 



(2) Large German silver wire, 



R=9'2xl0 9 , 

 and substituting in the series 



n [ L * 12 R* 180 R 4 + P 



R' = 9'2xl0 9 . 



(3j Large iron wire, 



R = 2-5xl0 9 , 



and if there is a true time lag, as often stated, such as to pre- 

 vent action of the magnetic property of the iron, and if on 

 this assumption we make /j>=1, 



R' = 2-78xl0 9 . 



(4) Fine copper, 



R=3'3xl0 9 , 

 R'=3-5xl0 9 . 



(5) Again, as before, call /jL=1 in iron, nickel, and steel. 

 The length of these circuits was 7*41 metres, the remainder 



of the 10*20 metres — 2*79 metres — being of copper wire of 

 R' = -94. The value of R' in the separate cases, including 

 in each the resistance '94 of the copper portion, was as 

 follows : — 



Soft iron 15*0 x 10 9 , 



Piano-steel... 20'7xl0 9 , 



Nickel 30-6 xlO 9 , 



German silver 23*0 x 10 9 . 



The ratio of the strengths of successive discharges during 

 the oscillation is given by the function 



where r is the ohmic resistance, T the time of a double 



