Oscillatory Discharges. 23 



Rectilinear Wire Calorimeter. 



Diameter Length, 



of wire, cm. cm. 



Calor. No. 4 ... 0-078 100 



„ „ 5 ... 0-078 147 



The constant o£ the spark calorimeter was found equal to 

 C 5 = 0*0429 cal./gT. For the remaining calorimeters we 

 found 



Ci=0"0668 cal./gr. 

 O 2 =0-0876 „ 

 C 3 = 0'0871 „ 

 C 4 = 0-0399 „ 



S. Resistance of Metallic portions of Circuit and its Dependence 

 on Nature of Discharge. 



23. We have already pointed out the importance that 

 an exact knowledge of the metallic portions of the discharge- 

 circuit had for our researches. 



In the case of common copper wires stretched out into a 

 straight line, the resistance R' opposed by a conductor of 

 length I to an oscillating current is given, according to Lord 

 Rayleigh*, by 



R 



1 dH 2 u 2 1 « 4 / 4 " 4 



V .12 R 2 180 R* + "7' * w 



R being the resistance of the same wire for continuous cur- 

 rents, /jl its magnetic permeability, and p = 27m, n being the 

 frequency of current. 



For the highest values of frequency, Lord Rayleigh's 

 theory shows that this resistance R' has a limiting value as 

 follows : — 



K>=4/m, ...... ( 2) 



or 



iijju 



o, being the diameter and a the specific resistance of the 

 conductor. 



This formula is equal to the one deduced for very high 

 values of n from the theory of electric oscillations in rectili- 

 near conductors developed by Stefan f. 



* Phil. Mag. [5] xxi. p, 781 (1886). 

 f YVied. Ann. xli. p. 400 (1SW). 



