Rowland Diffraction Grating

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This is one of the earliest concave metal gratings made on the ruling engine devised by Henry A. Rowland, professor of physics at The Johns Hopkins University in Baltimore. According to Rowland, it "was made for Professor Langley's experiments on the ultra-red portion of the spectrum, and was thus made very bright in the first spectrum. The definition seems to be very fine, notwithstanding the short focus and divides the 1474 line with ease." The reference here is to Samuel Pierpont Langley, the director of the Allegheny Observatory and professor of astronomy at the Western University of Pennsylvania (now the University of Pittsburgh). Langley became the third Secretary of the Smithsonian Institution in 1887. The grating measures 4 inches x 4.5 inches, and is marked "Rowland's concave grating Baltimore, May 12, 1882. 3610 lines to inch, radius 64".
Ref: Henry A. Rowland, "Preliminary Notice of the Results accomplished in the Manufacture and Theory of Gratings for Optical Purposes," Philosophical Magazine 13 (1882): 469-474.
Currently not on view
date made
Rowland, Henry A.
place made
United States: Maryland, Baltimore
overall: 10 in x 7 in x 3 1/2 in; 25.4 cm x 17.78 cm x 8.89 cm
overall; case: 10 in x 7 1/8 in x 4 in; 25.4 cm x 18.0975 cm x 10.16 cm
ID Number
catalog number
accession number
Credit Line
Smithsonian Astrophysical Observatory
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Medicine and Science: Physical Sciences
Science & Mathematics
Data Source
National Museum of American History


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