M. Dvorék—Acoustic Repulsion. 25 
only a short distance through the cork into the glass tube, 
placed upon a separate table so that its open end projects some- 
what beyond the edge of the latter. The length of the rod 
was 127 centimeters, the diameter twenty-seven millimeters ; 
the half wave length of its note, x equals ten and one-half 
centimeters. The length of the tube was 45 centimeters, the 
length of the vibrating column of air, corrected for the open 
end, was 35 + 7 the inner diameter was five centimeters. 
(3.) The Acoustic Torsion Balance.—If we hang by a wire a 
wooden rod provided with a resonator, like the beam of a 
Coulomb’s torsion-balance, in a case having an opening in the 
side turned toward the resonator, we can compare the intensity 
of notes having an equal number of vibrations by means of the 
repulsion of the resonator; but further experiments are neces- 
sary to test the practicability of this method. The sound pro- 
m 
tions), To prevent the current of air which passes through 
we must cut the pipe exactly in the middle of its node, and 
insert a slack membrane softened with glycerine. To prevent 
the air, issuing from the mouth of the pipe, from impinging on 
the resonator, a broad box is used which surrounds the mouth of 
the pipe air-tight. This box is open on the side opposite the 
resonator so as not to impair the tone. The pipe is sounded 
by means of a KGnig’s acoustic bellows with a uniform blast of 
air. ‘The distance of the resonator from the mouth of the pipe 
rod be at least two or three centimeters, to avoid a change of 
Itc 
(4.) Production of aerial currents by Sound.—It may easily be 
proved by simple theoretic considerations that the mean pres- 
sure at the node of a column of air is greater than at its ventre, 
and that it steadily diminishes in passing from the node to the 
Midas provided that the amplitude of vibration is not infinitely 
sma 
It would seem that this difference of pressure would be neu- 
tralized by the passage of the air from the node to the ventre. 
There would then be produced a mean pressure in the whole 
column, which would be greater, however, than that of air at 
equently air would issue from the opening of the 
oe et as 
vessel in which it forms stationary waves. I have not suc- 
ceeded so far in making the whole process clear, for in reality 
The maiometer 
no perfect balance of pressure takes place. neter 
always shows a slight excess of pressure even at the ventre, 
but this excess increases as we pass to the node. All my pre- 
lous experiments indicate moveover that a current of air 
