The tension coefficients of resistance of the hexagonal crystals, zinc and cadmium, have been measured. These coefficients have been found to be independent of the secondary orientation. This is in agreement with a theory set forth by P. W. Bridgman, as corrected by J. W. Cookson; furthermore the experimental points lie within experimental error of the curves given by the theory representing them as functions of the primary orientation. Cookson's correction gives the same formal dependence of the coefficients on the orientation as Bridgman's original theory, but demands additional constants fully to define the effect of deforming forces on the electrical resistance. Further experimental work will be necessary completely to determine this entire set of constants, and theory is sketched to show that torsion experiments would furnish the necessary data.

• Received 27 November 1935

DOI:https://doi.org/10.1103/PhysRev.49.248