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The internal friction in shear and modulus of rigidity of dry Solenhofen limestone has been investigated over a frequency range from 4 cps to 10 Mc/s at room temperature. The results found are: (1) The rigidity modulus is constant ( U = 2.64 × 1011 dynes/cm2) to within ±2 per cent over the total frequency range covered, provided that the samples have the same density. (2) The shear internal friction (as measured by the logarithmic decrement) in the cycle‐per‐second frequency range is about a factor of 5 lower than the internal friction in the megacycle frequency range; the logarithmic decrement at 4 cps = 3.4 × 10−3, the logarithmic decrement at 107 cps = 17 × 10−3. (3) The shear internal friction in the infrasonic frequency range increases by 18 per cent with the application of a 7.2‐kg/cm2 static axial tensile stress, but no large change in the internal friction occurs for axial compressive stresses of the same magnitude. (4) The shear internal friction is strain‐dependent even for strains as small as 10−6, a static axial tensile stress being superposed on the dynamic torsional stress.

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