M. Dvorék—Acoustic Repulsion. re 
air issues from the narrow end of the cone with such violence 
that it easily blows out of the flame of a candle at a distance 
of twenty centimeters. This current rushes through the cone 
with a peculiar noise and is easily felt with the finger. 
4. The cone may be replaced by 
a cylinder having the width of 
the Kundt’s tube, open at the 
end turned toward the latter, 
at the end, but the current is 
much weaker, nevertheless it 
will move a small wheel with 
vertical paper vanes, fig. 4. 
n the experiments with the 
tuning forks, it is essential that 
the cone should vibrate to the 
same note as the fork, otherwise 
the current is too weak. For 
the fork A (of 485 vibrations), 
i the openings of the cone have 
‘diameters of 82 and 8 millimeters, and the length 373 milli- 
meters. The opening at the apex of the cone must be very 
small to obtain an appreciable current. 
conclusion of this investigation, Dr. R. Konig ny 
communicated to me that Mr. Alfred Mayer in New Yor 
[Hoboken] had previously succeeded in producing continuous 
means 0 e 
rotation b The communication was as 
inform 
strated the phenomena of repulsion in resonators, for he was 
not acquainted with your paper* on acoustic attraction and 
repulsion.” 
Nore By Prorgessor ALFRED M. Mayer.—My connection 
with the discovery of the Sound-Mill is as follows: _ 
In January, 1876, I made the discovery—first reached by 
theoretic deductions—that there was more pressure on the = 
Inner surface of the bottom of a resounding cavity than on ~~ 
the outer surface of the bottom which touches the outer air. 
I subsequently proved the truth of this conclusion by expert 
ments on suspended resonators and by observations on the 
* Read before the R. Acad. Sci, Viennain 1875. 
