Bidwell showed that the resistance‐temperature law for certain variable conductors (oxides, etc.) was of the form &rgr; =AeQ/RT+aT. Plotted in the form (1/&rgr;)(d&rgr;/dT) =Q/RT2−ahe obtained for Fe2O3straight lines with a break near the recalescence point, the two lines having the sameyintercept but different slopes. This law was also followed by metallic germanium. The present paper extends this work to zinc oxide and beryllium oxide. Beryllium oxide yields a straight line showing a transition at 750°C. Zinc oxide yields two straight lines with a transition in the interval 250°C—500°C. The two zinc oxide lines have different slopes but the sameyintercepts. With successive heatings to 1050°C there occurs continued decreases in the slope of the line for the 500°C—1000°C range but no change in theyintercept. The line for the range 0°C—250°C changes on successive heatings to 1050°C and finally stabilizes to a value of slope and intercept which repeats on succeeding runs. On the suggesion that the indicated transformation was due to impurity, new material of special purity prepared by the New Jersey Zinc Company was studied. The behavior of this material was found to agree closely with that of the earlier specimen but gave a more clean cut transformation.