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Many experiments show that the long axes of the three extremely prolate ellipsoids which represent the electron Fermi surface in bismuth are tilted \ensuremath{\sim}6\ifmmode^\circ\else\textdegree\fi{} from the trigonal plane of the Brillouin zone; however, the sign of this tilt angle cannot be unambiguously obtained from the literature. We report results obtained from measurements of the de Haas-van Alphen and de Haas-Shubnikov effects and quadratic magneto-resistance which show that the sign of the tilt angle is positive in terms of the usual conventions, which are carefully defined. More explicitly, the long axis of each ellipsoid lies within the \ensuremath{\sim}18\ifmmode^\circ\else\textdegree\fi{} angle made by a bisectrix direction and a $\ensuremath{\Gamma}L$ direction in the Brillouin zone. Our results are shown to agree with the most recent band calculations for Bi. Comparison of de Haas-van Alphen results on Bi and Sb samples, each with the same orientation as determined by x rays, shows that, independently of any convertion, the tilt angles of Bi and Sb have opposite signs. We also clarify the procedures for properly orienting a crystal of bismuth by observing either twinning planes or etch pits in the trigonal plane.

It is pointed out that if the Kohn effect is looked for, not as an obvious kink in the phonon dispersion curves of metals as originally suggested, but as a damped sinusoidal variation of the interplanar force constants with separation, then (1) the effect has been observed in many metals and (2) for Na, which is very close to a free-electron metal, the measured force constants oscillate with the expected wavelength ($\frac{\ensuremath{\pi}}{{k}_{F}}$). From the data for Al and Pb, it would appear that even though the Fermi surface is quite close to a free-electron sphere in the extended zone, electrons do not scatter isotropically around this surface, but presumably stay within their respective Brillouin zones even at temperatures of the order of the Debye $\ensuremath{\theta}$.

The ratio of the $g$ value of potassium ${\mathrm{K}}^{39}$ in the ground state to the gyromagnetic ratio of the proton in mineral oil has been measured in an experiment combining atomic beam and nuclear resonance techniques. It is found to be $\frac{{g}_{J}(\mathrm{K})}{{g}_{p}}=658.2274\ifmmode\pm\else\textpm\fi{}0.0023$. This result, when combined with the measurement of $\frac{{g}_{J}(\mathrm{H})}{{g}_{p}}$ by Koenig, Prodell, and Kusch, yields $\frac{{g}_{J}(\mathrm{K})}{{g}_{J}(\mathrm{H})}=1.000016\ifmmode\pm\else\textpm\fi{}0.0004 \mathrm{percent}.$ This is to be compared with the recent direct measurement by Pohlman, Bederson, and Eisinger: $\frac{{g}_{J}(\mathrm{K})}{{g}_{J}(\mathrm{H})}=1.00016\ifmmode\pm\else\textpm\fi{}0.006 \mathrm{percent}$. The present experiment is of superior precision and is in agreement with independent experimental evidence. The present result is found to agree with the theoretically predicted value.