212 
PHYSICS: C. BARUS 
Proc. N. A. S. 
shell-like volume of the resonator IV cannot much have exceeded 10 or 
15 cm. 3 The tubes added 10, 17, and 24 cm. 3 , respectively. To this the 
shallow volume in the telephone (about 2 cm. 3 ) is to be added; neverthe- 
less the greater part of the total volume seems to reside in the tubes. 
The results obtained in the frequency survey for maxima and minima 
showed that the overtones had been differently accentuated. Thus the 
minimum near d" passes from positive to negative values as the tube 
length increases, while the reverse is observed at the maximum near g". 
The case for tube additions is then analogous to the occurrence of the 
vowel sounds, where different overtones are accentuated by variation of 
the mouth cavity. 
The Pinhole Sonde, or Probe. — The possibilities of sounding for pressure 
by aid of a pinhole valve, O, at the end of a slender tube, c (as in figure 2), 
communicating with the closed reservoir R' of the U-tube, the other, R, 
being open to the atmosphere are next to be treated. The telephone T 
was at first provided with a tubular projection t, 12 cm. deep to the plate 
and about .75 cm. in inner diameter. This received the probe c (0 being 
at the end of the aluminum tube C 2 mm. in bore, 3 mm. in outer diameter 
and about 20 cm. long) to different depths, with a view to exploring the 
pressure within. 
The results obtained on inserting the probe to different depths (marked 
in the graphs, data for 8, 10, 12 cm. of depth showing no further change 
in the telephone pipe) are given in figure 9, pressures laid off positively 
downward. The curves are unexpectedly complicated, but consistent, in 
their character throughout. In place of the simple distribution of pressure 
in the usual closed organ pipe, there is a maximum pressure increment near 
f , another at d" and a very pronounced pressure decrement (negative 
fringe displacement) near /". 
The increase of pressure from the mouth of t toward the telephone plate 
12.5 cm. below, is well shown in figure 10, in which the fringe displace- 
ments 5 for the large dilatation d" are recorded. The other curve gives 
the distribution of pressure at /". These increments rise very rapidly 
from the mouth inward and at 8 cm. of depth already reach a maximum 
value. Beyond this, the curves like figure 10 are apt to show a decrease, 
which is not probably incidental. 
The rubber tube was now about halved in length, the present depth to 
plate being about 5 cm. and the diameter .75 cm. The note obtained 
with the blower was a faint d' and a strong g". In the survey in pitch with 
the pinhole at a depth of 4 cm. there were maxima at d' and particularly 
at the octave of the blown pipe d", and minima at c' and a', all well marked. 
On comparison of the curve for the half pipe with figure 9, for the full 
pipe, there was actually a complete inversion of results, maxima taking 
