Oscillatory Discharges. 21) 



For the calorimeter No. 1 : 



R /=l-3 x 10-6 = 0-531) x 1-96 = 1-06; 



X ^'=3 xlO-6 -0-643 x2-i5 = l-38; 



R^ =2 -2xl0-6 = 0'761x 2-17 = 1-65. 

 For the calorimeter No. 3 : 



Rr / =1 . 7xl0 -6 = 0-440x 1-84 = 0-827. 



F. Self-Induction^ 



27. In the case of the self-induction also the theoretical 

 treatment with regard to alternating currents has been worked 

 out only for some special forms of plain circuits, and calcula- 

 tions relating to circuits w r ound into a spiral are completely 

 wanting, as in this case neither Maxwell's method of the 

 mean geometrical distance * nor Lord Rayleiglr's t method, 

 nor those derived from the theory of oscillatory discharges 

 may be made use of, as pointed out by Stefan %, 



As, how r ever, we wanted to ascertain this element also with 

 sufficient accuracy, we used the following circuits in our 

 experiments relative to the period measurements, the theo- 

 retical value of the self-induction being known in those 

 cases. 



(a) Square of copper wire : radius of section of wire 

 0*04 cm. ; length of side Z = 398*6 cms. 



(b) Circle of copper wire: — 



Circle No. 1 : radius of section of wire 0'226 cm. ; dia- 

 meter of circle 201 cms. 

 Circle No. 2 : radius of section of wire 0*226 cm.; dia- 

 meter of circle 57*2 cms. 

 The wires these circuits are made up of are stretched out on 

 suitable wooden frames, and the necessary insulation is obtained 

 by small ebonite cylinders. 



In order to keep the sides of the square as far as possible 

 from conductive masses during the experiments, the wooden 

 frame was inclined at 50 degrees to the horizon, and had one 

 side at the level of the spark-gap. The mean distance between 

 the sides of the square, the walls of the room, and the ceiling- 

 was 0*85 m. 



Now, according to Lord Rayleigh §, the effective self- 

 induction L' of a plane conductor, I in length and of an ohmie 



* Cfr. Wien, Wied. Ann. liii. p. 928 (1894). 

 t Phil. Mag. xxi. p. 381 (1886). 

 X Wied. Ann. xli. pp. 400 & 421 (1890). 

 § Phil. Mag. [o] xxi. p. 381 (1880). 



