The measurements described in the earlier papers of this series have been extended to 9400 Mc. /sec., a resonance technique being employed to determine the surface resistance of normal and superconducting tin, and the difference between the surface reactances of the material in the two states. Measurements on single crystals of different orientations have brought to light a marked anisotropy of all these quantities, of a kind which shows clearly the non-tensorial nature of the fundamental equations relating the field vectors. The prediction of the theory of the anomalous skin effect in normal metals, that the surface resistance should vary with frequency as
ω
⅔
, is confirmed. The temperature variation of the resistance and reactance of superconducting tin has been studied in detail for a number of specimens of different orientations, and it has been found that over certain ranges of temperature the shapes of corresponding curves for different specimens are similar, apart from scaling factors depending on the orientation; the values of these scaling factors are used to characterize the surface impedance of each orientation.
