Literature

1. Uspekhi fizich. nauk XIII, 783, 1933.
2. Debye, Proc. Nat. Acad. Am. 18, 409, 1932.
3. E. Hiedemann and A. Asbach, Phys. Z. 34, 393, 1933.
4. Schaffer and Bergmann, Sitzungsber. d. Preuss Akad. Wiss. X, 152, 1934.
5. Schaffer and Bergmann, Naturwiss. 22, 685, 1934.

L. Groshev

OPTICAL PROOF OF PIEZOQUARTZ OSCILLATIONS AT OVERTONES

By exciting piezoquartz with a variable wavelength and observing the formation of a diffraction pattern when a light beam is passed through a standing periodically distributed ultrasonic wave field, the author, by Debye’s method, demonstrated the excitability of quartz overtones (up to the 69th order). Measuring the distance between spectra and, from it, calculating both the oscillation frequency measured by a wavemeter and the velocity of ultrasonic oscillations in a liquid, the author found that it is constant in the frequency interval from \(3.65 \cdot 10^5\) to \(2.5 \cdot 10^7\) hertz (for toluene). By an analogous method the speed of ultrasound was measured in water, aqueous NaCl solutions, and chloroform, and data were obtained corresponding to those of other authors.

N. Malov

INVESTIGATION OF QUARTZ OSCILLATIONS WITH AN OPTICAL INTERFEROMETER

To determine the distribution of nodal lines and antinodes on the surface of an oscillating quartz, Osterberg (Osterberg, Phys. Rev. 43, 819, 1933) used a quartz plate as one mirror of an interferometer placed at a slight angle relative to the other mirror. In the absence of oscillations, parallel interference fringes were obtained, which were divided into separate sections when quartz oscillations were excited in a direction perpendicular to its surface. With such an arrangement it was impossible to obtain complete nodal lines. Therefore Straubel (H. Straubel, Phys. Z. 34, 894, 1933) placed the quartz strictly parallel to the interferometer mirror, and in the absence of oscillations the entire field of view was dark. When oscillations were excited, the nodal lines remained dark, while the moving regions became bright. By this method a study is being conducted of the oscillations of plates of various orientation, size, and shape; preliminary results of it are presented in the cited work.

N. Malov

FREQUENCY CONTROL USING A SINGLE-FILAMENT ELECTROMETER

To control the constancy of the frequency of an alternating current, an ohmic resistance and a capacitance connected in series are inserted into the circuit, their magnitudes being selected so that the voltage drops across both, at the given frequency, are equal. The filament of a single-filament electrometer is connected to the common point of the resistance and capacitance, while the electrometer legs are connected to the opposite ends of the resistance and capacitance. In this case the filament is set in a certain position, which it may leave when the distribution of voltage across the resistance and the condenser changes, caused by changes in the current frequency. It can be shown that the deflection of the filament is proportional to the change in frequency, so long as these changes are small relative to the magnitude of the original frequency (C. Hagen, Z. techn. Phys. 15, 231, 1934).

N. Malov