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Deppent. attained frequencies of 500—10000 complete periods p. S. 
SIMON increased the number of alternations so much, that the note 
emitted by the are ceased to be audible. He speaks of a limit of 
380000—40000 vibrations. From my tables will be seen that I have 
attained much higher frequencies, so high that I first distrusted them. 
But as yet L have not been able to find any inaccuracy either in 
the principle of the method or in its application. So T must think 
that my numbers are exact, the more so as they seem to be confirmed 
by a physiological estimate. With small frequencies, say up to 10000, 
the pitch of the note may be easily estimated by the ear when we 
produce two notes in rapid succession. In Series 1 I found that 
increasing the current from 1.9 to 2.2 ampere caused the pitch to 
rise about a “second”. By increasing from 2.2 ampere to 3.2 ampere 
the successive notes sounded as with a quint-interval. The later eal- 
culation of the frequencies from the galvanometer readings agreed 
fairly well with the estimated increase of pitch. 
The limit of audibility as calculated from the readings agreed 
equally with the limit as determined by the aid of a recently gradu- 
ated Ganton-whistle by Prof. EpELMANN, the graduation-table being 
verified on different points by myself. I found as a limit for the 
audibility about 48500 d.v.p.s. My are-lamp ceased to emit an 
audible note when the frequeney of 42000 was reached. In the 6% 
series no sound was heard at all. In the series 1, 2 and 3 the sound 
was heard throughout. In the series 4 I heard the note distinctly 
at 2.4 ampere; at 2,7 ampere I did not always hear the sound; 
only every now and then I got the impression of a very faint and 
high whistling sound. At 5.1 ampere I did not hear the sound. In 
the 5% Series the sound was always present at 3.6 ampere and 
sometimes at 3.7 ampere. 
As these results agree, I think that the method is a correct one, 
and that the higher numbers may also be relied upon. 
The sound of the singing are may prove perhaps valuable in 
physiological researches on sound. . 
The highest frequency with my apparatus was attained with a 
primary constant current of 4.2 ampere, /, = 36 Volt, 2, = 37.3 
Volt, J, = 0.49 ampere, C = 0.03 m.F., Ea being 9.7 Volt and 
p = 268000. Of course much higher frequencies may probably be 
attained. But the resistance of my hot-wire amperemeter was rather 
high, and I believe that therein lies an obstacle for my surpassing 
this limit. 
How are we to interpret the increase of the frequency caused by 
an increase of the constant current? There is some analogy with 
