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 EVIDENCE OF PIEZOQUARTZ OSCILLATIONS AT OVERTONES

By exciting piezoquartz with variable wavelength and observing the formation of the diffraction pattern when a beam of light is passed perpendicular to the propagation of ultrasonic waves, Debye’s method was used by the author to prove the excitability of quartz overtones (up to the 69th order). By measuring the distance between the spectra and calculating from it, as well as from the frequency of the oscillations measured with a wavemeter, 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 \(2.5 \cdot 10^7\) Hz (for toluene). An analogous method was used to measure the velocity of ultrasound in water, aqueous NaCl solutions, and chloroform, and data were obtained that agree with those of other authors.

N. Malov

STUDY OF QUARTZ OSCILLATIONS WITH AN OPTICAL INTERFEROMETER

To determine the distribution of nodal lines and antinodes on the surface of oscillating quartz, Osterberg (Osterberg, Phys. Rev. 43, 819, 1933) used a quartz plate as one mirror of an interferometer, placing it at a slight angle relative to the other mirror. In the absence of oscillations, parallel interference fringes were obtained, which separated into individual 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. Upon excitation of oscillations the nodal lines remained dark, while the moving regions brightened. By this method the study of oscillations of plates of various orientation, size, and shape is being carried out; preliminary results are presented in the cited work.

N. Malov

FREQUENCY CONTROL BY MEANS OF A SINGLE-FILAMENT ELECTROMETER

To monitor the constancy of the frequency of an alternating current, an ohmic resistance and a capacitance connected in series are included in the circuit; their magnitudes are chosen so that the voltage drops across both, at the given frequency, are the same. The filament of a single-filament electrometer is connected to the common point of the resistance and the capacitance, while the electrometer plates are connected to the opposite ends of the resistance and the capacitance. In this arrangement the filament is set in a certain position, which it may leave when the voltage distribution across the resistance and condenser changes owing to changes in the current frequency. It can be shown that the deflection of the filament is proportional to the change in frequency, as long as these changes are small relative to the magnitude of the initial frequency (C. Hagen, Z. techn. Phys. 15, 231, 1934).

N. Malov