Rowland Diffraction Grating

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Henry A. Rowland, a professor of physics at The Johns Hopkins University, designed an engine that produced diffraction gratings by ruling a large number of closely spaced lines on a metal surface. The concave speculum metal mirrors for many of these gratings were ground and polished in John A. Brashear's shop in Pittsburgh. The mirrors were sent to Baltimore, where Theodore C. Schneider ruled them with Rowland's engine, and then returned to Pittsburgh for sale to scientists around the world. This one is marked “Ruled by Schneider on Rowland's engine 14438 lines per inch Johns Hopkins Univ. Feb 1884 definition good. Ruling third class.”
Currently not on view
date made
Rowland, Henry A.
place made
United States: Maryland, Baltimore
overall: 3 cm x 12 cm x 12.5 cm; 1 3/16 in x 4 23/32 in x 4 29/32 in
overall: 1 1/4 in x 4 5/8 in x 4 5/8 in; 3.175 cm x 11.7475 cm x 11.7475 cm
ID Number
accession number
catalog number
Credit Line
U.S. Military Academy
See more items in
Medicine and Science: Physical Sciences
Science & Mathematics
Data Source
National Museum of American History


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