Oscillatory Discharges. 637 



Part V. Measurements of Energy spent in the 

 Different Parts of the Circuit. 



38. The expression 



W=i0V«, 



where C is the capacity of the condenser, and V the potential 

 it has been charged to, gives the maximum limit of the 

 energy the condenser is capable of supplying on its being 

 discharged through any circuit. 



Now when the discharge occurs, part of the energy the 

 condenser possesses is dissipated in the dielectric ; another 

 part is employed to overcome the resistance of the circuit and 

 of the spark; a third part is spent in splitting metallic particles 

 off from the electrodes, and in causing them to glow ; and a last 

 part will finally be (radiated) sent off from it, viz., will be 

 spent in the production of the electrostatic and electro- 

 magnetic fields. It is evident that these various portions 

 will not all be found again under the form of thermic energy 

 in the discharge-circuit — comprising the spark ; and that it 

 will be necessary to account for the means of measuring the 

 single portions themselves. 



Direct determinations of the energy dissipated elsewhere 

 than in the metallic part of the circuit and the spark have 

 only been made as far as the amount absorbed by the dielectric 

 of the condenser is concerned ; and some are relative to the 

 case of alternating currents supplied by ordinary industrial 

 machines, as those of Rosa and Smith "*, of Lombardi f, 

 Arno J, and Schaufelberger §, &c. But in our case the loss 

 of energy in the dielectric of the condenser may be neglected, 

 as we used an air-condenser. 



Among the investigations performed in order to determine 

 the heat evolved in the spark and in the metallic part of a 

 discharge-circuit, we wish to mention those of Heydweiller 

 and Cardani, as they were made with a special view to 

 determine quantitatively the phenomenon. 



Heydweiller's || measurements relate only to continuous 

 discharges, as he inserted in the circuit resistances of several 

 megohms formed by solutions of cadmium iodide in amy] 

 alcohol. 



* Phil. Mag. [5] xlvii. p. 19 (1899). 



f Lombardi, Abstracts from the JBlettricista, Year 5, No. 10, Mem. 



R. Ace. Sc. Torino, ser. ii. vols. xliv. & xlv. 

 % Rend. Ace. Line. 1892, 1893, 1894, 

 § ' Inaugural Dissertation ' (Faculty of Zurich), 1898. 

 || Wied. Ann. xliii. p. 310 (1891). ' 



