(406 ) | "es 
The reason for this is 1. that the current induced in the second- 
ary is weaker for 15 A (for instance) than for 3 A, and 2°. that 
the secondary turns are farther removed from the iron in 15 A 
than in 3A. This is also proved by the following experiment: d 
I took the coils 3 A and 15 A of fig. 7 (changed into telephones) _ 
and again arranged the experiment as in fig. 8. The tuning-fork 
was placed near the resonator, the microphone-battery consisted of 
a storage-cell. Both telephones, the secondaries being open, gave a 
strong sound. If the secondary of 3 A was closed, the sound produced 
by this telephone, became perceptibly weaker; if the secondary of 
15 A was closed, there was no difference perceptible in the intensity 
(though there was in the quality). The same experiment was repeated 
after the storage-cell had been exchanged for a Leclanché-cell, i.e. with 
a weaker undulating current. With coil 3 the closing of the secondary 
produced a very perceptible weakening of the sound; with 15 now 
a slight weakening of the sound was noticed when the secondary wire 
was closed but it was extremely small. ') 
When we divide the numbers, found on page 367 for the effect of _ 
; : A RE 
the various A coils, by the values of B found on page 402, we obtain 
for the effect of the various B coils: ~ 
| | 
15 
Coil: s |s | 9 oe 
Strength of the induced current of | 
the A coils: | | | 
A. 
en 
Strength of the induced current of | | | 
the B coils: | pe | 
1) At first it was my intention in writing this paper not to mention the experiment 
of fig. 14, the question concerning the influence of the iron being to my idea saffi- 
ciently answered. But on the other hand it seemed to me that these numbers could 
serve to heighten the trustworthiness of the other results arrived at by me, as the 
reason of the differences between the numbers of the two rows on page 405 was, to 
my idea, perfectly explained. And where quantitative investigations are made with 
such capricious apparatus as microphones and electro-magnetic tuningforks, an indi- 
rect confirmation seemed not superfluous. 
