( 363 ) 
they were used by me, the deviations of the electro-dynamometer 
were proportional to the square of the mean intensity of the current. 
I set to work as indicated in fig. 2. 
The microphone was connected with an accumulator and the 
primary wire of coil 3A. As is the case with all the experiments 
described in this paper, the resonator Fa 3 and the tuning-fork Fa 3 
were placed before the microphone. One of the ends of the secon- 
dary wire of 3.A was connected with the electro-dynamometer and 
moreover with the pivot of a Morse-key; the other end of the 
secondary wire with the pivot of a 22d Morse-key. The contacts 
of rest of the keys were connected with each other; the working 
contacts likewise, but with that wire were connected: 1°. a coil of 
wire, a, in which a bundle of ironwires was placed under an angle 
of 45 degrees to the plane of winding, quite similar to the coil 
and the bundle of ironwires of the electro-dynamometer ; 2°. the 
secondary wire, b, of coil 3 B, into which however for this experiment 
an iron core had been put. 
If the Morse-keys were not pressed down, the current induced in 
3 A passed to the electro-dynamometer and thence along 9, 5, 6, 10 
back to the secondary wire. If however both keys were pressed 
down, the current had to pass along 9, 1, 4, b, 2, 10 and so passed 
through a 2d Bellati-coil and a 2d secondary wire. In that case the 
resistance as well as the self-induction of the secondary circuit was 
doubled and consequently the strength of the current reduced to half 
its former intensity. 
The relation between current-strength and deviation I have deter- 
mined for three different currents. In the first case the deviations 
with the currents 7 and 27 were respectively 118'.9 and 4811.7; 
in the second case those deviations were 93'.1 and 350'.4 and in 
the third case 21'.9 and 85'.1. 
Three successive turning-points were always observed; the posi- 
tion of rest was calculated according to the well known formula 
Pi Ps 
‘ea 
further description is superfluous on account of Table II (p. 364), 
giving the entire measurement of the 24 of the above-mentioned 
cases. 
In this way I found in the three different measurements the 
numbers 4.05, 3.76 and 3.89 for the relation between the deviations 
brought about by the currents 2i and i. The mean of these 
three values is 3.9. So for our further measurements we can assume 
Po = P2 + from p‚ and ps as well as from pz and ps. A 
