- 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 example was probably used by Peter Smith Michie, the Army Engineer who, in 1871, became Professor of Natural and Experimental Philosophy at the U.S. Military Academy. Michie was also the first American academic to recognize Rowland’s first important scientific paper. And it was he who, in 1875, suggested that Daniel Coit Gilman, recently named founding president of The Johns Hopkins University, consider hiring Rowland to teach physics at the new university.
- The inscription on this example reads “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.
- 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
- Data Source
- National Museum of American History
Our collection database is a work in progress. We may update this record based on further research and review. Learn more about our approach to sharing our collection online.