( 312 ) 
DvuppELL believed that the frequency was determined by the self- 
induction and the capacity according the well-known formula : 
p= 2aVel. 
Paut Jannr thought the same and proposed, as DupperL had 
already done before, to use the singing are for measuring small 
coefficients of self-induction. 
In the way proposed by JANrT, this seems to be impossible as the 
frequency depends not only on the self-induction and the capacity 
but i.a. also on the strength of the constant current. 
I have investigated the variation of the frequency caused by varying 
the constant current, the results being stated in this paper. 
The experiments were carried out after Prukert’s method. The 
P D at the solid carbons was measured by a Weston-instrument, 
that showed the Volts of the constant current only, and at the same 
time by a hot-wire Voltmeter. Lastly the current in the condenser- 
circuit was measured by means of a hot-wire amperemeter. The 
three readings being 4, EF, and /,, the frequency may be cal- 
culated by 
/ 
2 
P = Sr res 
Zacv EE, 
c being the capacity of the condenser in farads. 
The necessary correction of the instruments was known and has 
already been applied in the tables. The arc-lamp used was a small 
shunt-regulator by KörtinG & MATTHIESEN. 
Series 1. Capacity 2,68 ml’. Selfinduction: bronze wire spiral of 
80 windings; air isolation ; diameter 25 centimeter, height 50 centimeter. 
The table contains in the 
Ist column: Z, the constant current through the arc. 
Qnd- oy E,‚ the constant current PD of the carbons. 
ord hi KE, the hot-wire voltmeter reading. 
Ath, E, the value of V #,2—E,? being the superposed 
alternating volts. 
oth ” /, the alternating current strength. 
ee p. the number of complete alternations p. s. calculated 
by PevKerT’s formula. 
