12,795. Fraser & Chalmers, and Behr, H. C. May 30. Stamps, ore and like. -In a fluid - operated ore stamp, the cylinder cover 13, Figs. 1 and 3, or an inner sleeve 13, Fig. 17, or the whole cylinder 8, Fig. 19, is adjusted as the stamp 2 wears, so that the upper clearance of the piston 7 and the length of stroke remain constant.