Rowland Diffraction Grating

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
Object Name
diffraction grating
date made
Rowland, Henry A.
overall: 3 cm x 12 cm x 12.5 cm; 1 3/16 in x 4 23/32 in x 4 29/32 in
place made
United States: Maryland, Baltimore
ID Number
accession number
catalog number
Science & Mathematics
See more items in
Medicine and Science: Physical Sciences
Data Source
National Museum of American History, Kenneth E. Behring Center
Credit Line
U.S. Military Academy

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