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1023of Terrestrial Magnetism. The protons scattered from a thin carbon target on a silver leaf backing were counted with an argonfilled proportional counter biased to count only those protons near the end of their range. The ratio of the number scattered by carbon to the number scattered by silver determined the ratio of the cross sections except for a constant multiplying factor due to the difference in the number of carbon nuclei and silver nuclei. Since the ratio of cross sections was determined the target thicknesses were not determined, but both targets were thin; and since both targets were bombarded at the same time the geometrical factors cancel. The protons scattered from the two different nuclei can be resolved because of the difference of the recoil energy of the nuclei.Number vs. range curves were determined at 55°, 90°, 132.5°, and 160° in the laboratory system for bombarding energies of 2.5 and 2.75 Mev and at 90°, 132.5°, and 160° for energies of 2.0 and 2.25 Mev (Fig. 1). The area under a peak minus a fixed area determined by the channel width of the detecting system, which is a function of the effective counter and depth and the bias of the system, is proportional to the intensity. The channel width is defined here as the intercept of the curve of widths of the proton peaks at half-maximum vs. range in air at zero range. The slope of this curve is very nearly the slope of the range straggling curve computed for widths at half-maximum. 1 The area under the peaks was measured with a planimeter; several independent measurements were made for each area and the ratio of the average values was used.The half-widths due to straggling and channel width were assumed to add as the sum of the squares then the ratio of areas was corrected for channel width by multiplying by [(o-obs where a 0 bs is the observed width at half-maximum and a c h is the channel width. The ratio of the areas was also transformed to the carbon center-of-mass system, assuming that the silver scattering is classical.The corrected area ratios vs. angle in the carbon center-of-mass system are shown in Fig. 2. The dotted line is 2 R() at 2.5 Mev for 5-wave scattering, with 5 0 at 125° as determined by Heitler 2 ei al. y normalized to 0.1 at 60°. The error of ±10 percent consists principally of the statistical counting errors, errors in area measurement, and errors in measuring the widths at half-maximum. Except for the 2.0-Mev curve the curves all show a definite tendency to decrease at the larger angles and this probably 50 60 70 80 90 K)0 110 120 130 140 150 160 ANGLE IN THE CARBON CENTER OF MASS FIG. 2. The ratio S of the areas under the peaks vs. angle in the carbon center-of-mass system. Dotted line is R() for 80=125° at 2.5 Mev. See reference 2.means that the P wave is becoming effective. More precise curves are necessary if the P-wave and 5-wave components are to be determined accurately.

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Hall-and Seebeck-data of reduced and lithium-doped rutile both with and without alumina added are reported. The data are interpreted by a one band model. Anisotropy of the relaxation time must be taken explicitly into account. The donors in reduced rutile are probably titanium interstitials, which are multiple donors. The first and second of their ionization potentials are derived from the experimental data. Lithium is a single shallow donor. It is demonstrated that aluminium introduces more than one acceptor level. One of these levels is situated close to the conduction band.

The thermal conductivity of single crystalline BaTiO 3 has been measured in the temperature range of 100-500OK. In the neighbourhood of the transition temperature a reduction of the thermal conductivity is observed. This result can be explained in view of a current theory on ferroelectricity which introduces the concept of low frequency ferroelectric modes of lattice vibration.Optical phonon effects in thermal conductivity studies have been reported before [1][2][3].In this note we report measurements on BaTiO 3 near its transition temperatures that differ from previous measurements [4][5][6]. We believe to see the influence of low lying transverse optical phonon branches. Our way of reasoning can also be applied to measurements on other single crystalline ferroelectric materials near their Curie temperature [7,8].Thermal conductivity measurements have been performed by a steady state heat flow method [9] in a temperature range of 100 -500°K. Differential thermocouples of copper-constantan were used. A Leeds and Northrup K3 potentiometer together with a Hewlett and Packard 419-A d.c. null detector were used for the thermocouple measurements. The temperature difference was of the order of one to four degrees centigrades. The sample of roughly three milimeter diameter and one milimeter thickness, was grown by floating zone process [10] with a Sr dope of 1.5%. At room temperature under a polarizing microscope it showed a multidomain structure. The heater and the thermocouples of 0.05 mm diameter were glued to the sample and the sample to the heat sink by a high temperature-setting epoxy resin.The result of the measurements is shown in fig. 1. The curve shows dips in the neighbourhood of the transition temperatures. At the high temperature side it is rising. We expect it to merge to a higher lying curve that has a T-1 dependence at these temperatures.

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