152 THE ELECTRIC ARC 



surrounding gas is helpful, and surrounding the arc with 

 steam, coal gas or hydrogen gives better results. 1 



The time that is taken for charging and discharging the 

 condenser depends on the capacity and inductance of the 

 condenser circuit. The period of the swing would equal 

 2 irVLC, if the resistance of the arc were constant, and it 

 was indeed suggested by Janet 2 that use could be made of 

 this fact to determine the coefficient of inductance of any 

 circuit placed in series with the condenser. However, the 

 very existence of the phenomenon depends on the fact 

 that the resistance of the arc is not constant and it has been 

 shown that the period of oscillation depends not only on 

 the capacity and inductance, but also on several other of 

 the conditions under which the arc is working, so that this 

 method can not be used in determining inductance. 3 



The charging and discharging of the condenser produce 

 electric waves and it is possible to make use of these in 

 wireless telephony, but in order to send a sufficient amount 

 of energy out into space, it is necessary to have high fre- 

 quency. Many arcs which show steep characteristic curves 

 for slow changes do not have steep curves when the changes 

 are very rapid, as has been shown by Duddell for carbon 

 arcs. If, therefore, oscillations are to be produced, it is 



1 A very complete review of this subject showing oscillographs of several 

 different arcs has been given by Blondel. (Eel. Elec., 44, 41 and 81; 1905.) 



2 C. R., 134, 462 and 821; 1902. 



3 Ascoli and Manzetti, Rend. Ace. Line., (5), n, 2 sem. u; 1902. 

 Corbino, Sc. Ab., 7, 537; 1903. 



Duddell, Lond. Elec., i, 902; 1903. 



Maisel, Phys. ZS., 4, 532; 1903. 



Salomonson, Sc. Ab., 6, 167; 1903; Eel. Elec., 34, 202; 1903. 



Granqvist, Boltzmann Festschrift, 799; 1904. 



Heinke, Ver. d. Ver. z. Beford. d. Gewerbfleisses, 83, 403; 1904. 



Nasmith, Phys. Rev., 27, 117; 1908, and 32, 69; 1911. 



