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The method of measurement of the dielectric properties of solid dielectrics described by S. Roberts and A. von Hippel has been applied with 3-cm wave-length waves in a rectangular wave guide. In this method the dielectric sample is placed at a short circuited end of the transmission line, and the dielectric properties of the sample, calculated from the position of a minimum of the standing wave and the ratio of the minimum field strength to the maximum field strength of the standing wave. A simplified procedure for calculating the dielectric properties from the measurements is presented. Values are given of the dielectric properties of some common plastic and ceramic materials at lO-cm wave-length and 3-cm wave-length, which were measured with this method.

the absorption line due to the transition from the /= 1 to the / = 2 molecular rotational level has been resolved and shown on an oscilloscope. This line appears at the frequency of 24,320 megacycles or 0.8107 (cm -1 ) wave numbers. The line was resolved at pressures of less than 10" 1 mm of Hg. At pressures greater than this, the pressure broadening of the line was so great that the line was hardly observable by the oscilloscope method. The gas was introduced for the measurements, into a rectangular wave guide through which the microwaves were transmitted. Further details concerning the method can be found in the paper cited.Carbon oxy-sulphide, OCS, is a linear molecule with the carbon atom between the oxygen and sulphur. Its moment of inertia calculated from the above frequency is 1.379 X10" 38 g cm 2 .The value (1.38X 10~3 8 g cm 2 ) calculated using the interatomic distances observed by Cross and Brockway, 2 agrees well with this.A linear molecule of this sort should show a Stark effect shift and splitting proportional to the square of the electric field strength and the square of the dipole moment. 3 When a d.c. electric field was applied to the carbon oxy-sulphide in the wave guide with the d.c. field parallel to the direction of the polarized electric vector of the traveling microwave, the rotational line split into two lines. One of these lines moved to a lower frequency than the unperturbed transition line and the other moved to a higher frequency. This effect was instantly (and to the authors, spectacularly) observed on the oscilloscope screen as the d.c. voltage was gradually increased. The single peak observed on the oscilloscope divided into two peaks, one of which was twice as high as the other. Figures 1-3.The line which showed the least shift appeared twice as high (intense) as the other, in agreement with the theory. The energy level for the positive external (spatial) quantum number is the same as for the negative. Therefore, the 2(/-f-l) states become only (7+1) levels. The frequency shift was found to be proportional to the square of the electric field strength, agreeing with the theory. Because the d.c. electric field is in the direction of the electric vector of the traveling microwave, no transition in the external quantum number occurs here when the rotational quantum number changes. Therefore, the frequency separation of the two lines from each other should be:where p is the dipole moment and E the d.c. field strength. From the above equation the observed value of A/ and I, the moment of inertia, the dipole moment can be calculated. It was found to be 0.72 X10~1 8 e.s.u. The principal uncertainty in the measurement is the separation of the THE EDITOR FIG. 1. FIG. 2. FIG. 3.FIGS. 1-3. Oscilloscope pictures of absorption versus frequency for the OCS rotational line at 24,320 megacycles. The applied d.c. volts is 0 volt/cm in Fig. 1, 750 volts/cm in Fig. 2, 1070 volts/cm in Fig. 3. The frequency markers in the oscilloscope pictures are 6 megacycles apart in each case and appear as points of...