Resistance change of single crystal Bi as a function of magnetic field intensity.—Bismuth crystals of various orientations (angle between vertical crystallographic axis and length of specimen) show an increase in resistance in a magnetic field parallel to the specimen length. The fractional change in resistance $\frac{\Delta r}{r}$ is shown to be proportional to a power, slightly less than two, of the field intensity. In a maximum field of about 3500 gauss and at room temperature the increases in resistance range from 2 to 9 percent.

Resistance change of single crystal Bi as a function of orientation.—For a constant magnetic field (3480 gauss), the change in resistance when plotted against crystal orientation, shows maxima at orientations of 63° and 80°, and minima at 0°, 73°, and 90°. This effect is substantiated by observations on specimens whose orientations have been changed by grinding or splitting, since these show the same type of variation with orientation as do the separate crystals. To determine whether the effect is due to a lack of rotational symmetry about the vertical axis some experiments are described in which the position of the vertical axis was kept fixed and the position of a minor (digonal) axis varied slightly. No observable change was found.

Specific resistance.—The specific resistance, as a function of crystal orientation obeys the Voigt-Thomson symmetry relation. Comparison with recent results by Bridgman show a considerable difference, the explanation of which has presumably been given by Bridgman.

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