Ultrasonic pulse measurements in the 3 to 10 mc./sec. frequency range were made of shear and dilatational absorption and velocity for three samples of fine-grained, homogeneous, and well-compacted limestones at atmospheric conditions. The complex moduli of elasticity were calculated for two limestone specimens of different grain size and porosity. A "hysteresis" or "solid-friction" type of loss for waves of dilatation was found in all three limestone specimens. Shear measurements made in one of the limestones also show a "hysteresis" type of loss. Comparison of the dilatational loss in a single crystal of calcite to the dilatational loss in the limestones indicates that the internal friction for the limestone specimens probably occurs at the grain boundaries.

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