Diffraction Grating
date: label: date made
content: 1882
name: label: maker
content: Rowland, Henry A.
notes: label: Description
content: This is one of the earliest concave metal diffraction gratings made on the ruling engine devised by Henry A. Rowland, professor of physics at The Johns Hopkins University. It measures 4 inches x 4.5 inches. The inscription reads "Rowland's concave grating Baltimore, May 12, 1882. 3610 lines to inch, radius 64". 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."
label: Description
content: At the time this grating was made, Samuel Pierpont Langley was serving as the director of the Allegheny Observatory and professor of astronomy at the Western University of Pennsylvania (now the University of Pittsburgh). He apparently brought this grating to Washington in 1887 when he became the third Secretary of the Smithsonian Institution. And he apparently left it at the Smithsonian Astrophysical Observatory, an organization he established soon thereafter.
label: Description
content: Ref: Henry A. Rowland, "Preliminary Notice of the Results accomplished in the Manufacture and Theory of Gratings for Optical Purposes," <i>Philosophical Magazine</i> 13 (1882): 469-474.
label: Location
content: Currently not on view
place: label: place made
content: United States: Maryland, Baltimore
setName: label: See more items in
content: Medicine and Science: Physical Sciences
label: See more items in
content: Science & Mathematics
creditLine: label: Credit Line
content: Smithsonian Astrophysical Observatory
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: PH.316865
label: catalog number
content: 316865
label: accession number
content: 228767
objectType: label: Object Name
content: diffraction grating
physicalDescription: label: Measurements
content: overall: 10 in x 7 in x 3 1/2 in; 25.4 cm x 17.78 cm x 8.89 cm
label: Measurements
content: overall; case: 10 in x 7 1/8 in x 4 in; 25.4 cm x 18.0975 cm x 10.16 cm