Vol. 8, 1922 
PHYSICS: C. BARUS 
67 
ward, at 2; = 40 cm. above the origin of the table, came out with surprising 
definiteness at once. They will therefore aid in disentangUng the mysterious 
behavior of the resonator elsewhere observed (cf. Science). The resonator 
R, fig. 6, pin-hole tube qo, was placed on the table, horizontally, with the 
mouth toward the pipe (azimuth 270°). The vertical board or reflector 
4 feet X 1 foot placed normal to y, was then moved successively from y = 
20 cm. (about at the mouth of R) nearly to the wall W at y = 174 cm. 
The results are given in figure 1 where 5 is the fringe deflection of the U- 
tube interferometer. The chief maxima are near y = 50, 100, 150 cm., 
which suggests the wave-length of the f pipe X = 48 cm., here operating 
by oblique reflection. Between the maxima X and 3X, there is a sub- 
sidiary maximum which one might erroneously attribute to overtones, 
inasmuch as it is often associated with weakly or strongly blown pipe notes. 
Thus at ;v = 80 the largest deflection is obtained from the dying note. 
at 90 from a forced note; but the 2X crest is regular. Distances between 
150 cm. and the wall W at 174 cm., were not available. A remarkable 
feature of the curve is the strong initial minimum at = 40 cm. If 
the board is placed more or less obliquely to y, the minimum tends to vanish, 
as shown by the successive tests at 0' and 0. 
In the disposition given, two sound rays reach the resonator, one re- 
flected from the board and the other direct, with immediate reflection 
from the table. When the board is near the mouth of the resonator, 
these rays are reduced to one and the result is an accentuated maximum. 
As the board distance in y increases, the path difference steadily increases 
with a simultaneous weakening of the reflected ray ; nevertheless the figure 
proves conclusively that it is not as ineffective as one might suppose. 
In contrast with the preceding, the next graph, figure 2, for the same pipe 
position, but with the resonator on the table at ;v = 0 cm. (in azimuth 
