This concave metal grating probably belonged to Samuel Pierpont Langley, director of the Allegheny Observatory and professor of astronomy at the Western University of Pennsylvania (now the University of Pittsburgh). It probably came to Washington in 1887 when Langley became the third Secretary of the Smithsonian Institution.
The inscription reads "plate polished and corrected by J. A. Brashear Pittsburgh, Mar. 1886 Radius 64 Ruled by Schneider on Rowland engine Johns Hopkins University April 1886 - lines to in temp-".
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