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The right hand picture shows a specimen that has been deformed in torsion in the Paterson deformation apparatus. Axis of rotation is vertical; rotation of specimen was top to the right. The specimen is encapsulated between pistons using an iron jacket. The jacketed sample is 15 mm wide.

The left hand picture is a photomicrograph of a thin section of a Carrara Marble specimen that has been deformed in torsion at 900°C and 300 MPa confining pressure. The cut is perpendicular to the axis of rotation and there is a strain gradient, minimum at the top of the picture (near the center of the sample), maximum at the bottom of the picture (near the outer edge of the sample). The average grain size at the top of the picture is 200 microns. The fine grains seen around the large grains at the bottom of the picture are recrystallized grains.