. Carnegie Institution of Washington publication. 32 DISPLACEMENT INTERFEROMETRY APPLIED TO edly 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 decrement near f't another at d", a maximum nega- tive pressure increment near a', and a very pronounced positive pressure increment near f". A pipe of the same length, if wide and uniform, would have responded to e". The low pitch is thus attributable to the plate space in the telephone and possibly to the narrowness a
. Carnegie Institution of Washington publication. 32 DISPLACEMENT INTERFEROMETRY APPLIED TO edly 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 decrement near f't another at d", a maximum nega- tive pressure increment near a', and a very pronounced positive pressure increment near f". A pipe of the same length, if wide and uniform, would have responded to e". The low pitch is thus attributable to the plate space in the telephone and possibly to the narrowness and roughness of the tube, which was of hard rubber. However, the increase or decrease of pressures respectively, from the mouth of t toward the telephone plate cm. below, is well shown in figure 47, in which the fringe displacements s for the large minimum d" and the large maximum f" are recorded. Pressure rises (or falls) very rapidly from the mouth inward and at 6 or 8 cm. of depth already reaches its maximum value. Beyond this the curves of the figure often show a decrease, which is probably not incidental (owing, for instance, to a heated telephone or to inevitable changes in the motor-break inducing current, during so protracted a series of observations), as it occurs frequently below. A cylindrical enlargement was now attached to the pipe t, figure 43, con- sisting of a glass tube (see fig. 48) 9 cm. long and cm. in diameter, tapering to a narrow tube fitting t, the total length of which was now 15 cm. Explor- ations were made with the probe in the wider tube, with results also shown in figure 48, at i, 4, 6, 8 cm. from the end of the tube. These results (pressures positive upward) are again consistent. There are two definite maxima, one near a' and the other (uncertain) near d". The latter may be a residue of the case, figure 45, but the former is surely a repetition of the a'. Naturally, pres- sure increments in figure 48 are much smaller; for th
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