Rutherford. — On the Magnetization of Iron. 511 



•where L = inductance of circuit for rapid oscillation, 



R = resistance of leads and spark-gap, 

 C = capacity of jar, 

 V = potential of coatings. 



The maximum current of the first half -oscillation is 

 given by 



R T 



T- CV ° /2L'j 

 Jl ~ (LC)* 



where T is period of a complete oscillation. 



The maximum current of the second half-oscillation is 

 given by 



- JL • 3 T 



T CV o - 2Jj \ 



d 2— (LCji e 

 " ° - 2L 2 l A -J 



The ratio j- can be obtained by the method of experiment 



previously explained ; and, since T and L are known from the 

 data of the condenser and the discharge circuit, R is known. 

 Now, R is made up of the resistance of the leads as well as the 

 spark-gap. The resistance of the leads can be deduced from 

 Rayleigh's formula, and therefore the resistance of the spark- 

 gap between the first and second half-oscillations is known. 



An experimental method of calculation was also used as a 

 means of checking the results obtained from above equation. 



After the ratio ~ had been determined by varying the number 

 of turns in a solenoid, a known carbon resistance,, r, was intro- 

 duced into the circuit, and the ratio, ~r~, of the first two half- 

 oscillations determined as before. 



. . J s _ (R + r) T _ , 



•• lQ g- J7 2L • 2- ( B -) 



Dividing equation (B) by (A), we get — 

 B+r_'°g-7r 



E " log- 4 1 



Therefore R is known at once. 



Proceeding in this way, the resistances of spark-gaps when 

 the self-inductance and spark-length were constant and the 

 capacity varied were determined. The spark-gap was T : oin. in 

 length, and between knobs 1cm. in radius. 



