Spectrograph

Object Details

Description

This large instrument was built at the National Bureau of Standards and, by producing precise wavelength measurements, many of them in the infra-red, facilitated the large expansion of applied spectroscopy. Much of this work was done by William F. Meggers (1888-1966), a physicist who joined the Bureau as a laboratory assistant in 1914, at the time the spectrograph was put into operation. After receiving a Johns Hopkins PhD for his work with this instrument, Meggers served as Chief of the Spectroscopy Section of the Bureau from 1920 until his retirement in 1958.

This spectrograph incorporates a concave speculum metal grating with a 21-foot radius of curvature. The plate was probably figured by John A. Brashear in Pittsburgh, and the ruling, 15,000 lines per inch, was produced on the Rowland engine at the Johns Hopkins University. The legs and plywood box were added in 1949.

Meggers explained that, in this instrument, “the slit is, in effect, placed at infinity with the aid of an auxiliary mirror, thus filling the concave grating with parallel light [and giving] spectral images which are practically free from astigmatism.” The form had been developed by Frank L. O. Wadsworth (1867-1936), an engineer from the Ohio State University who worked for Albert A. Michelson at Clark University, at the Yerkes Observatory, and then as Director of the Allegheny Observatory. Wadsworth later worked for the Pressed Prism Plate Glass Company in Morgantown, WV, and the Miller Non-Corrosive Metal Company in Pittsburgh, served as a consultant to Brashear, and obtained numerous patents.

Ref: W. F. Meggers, “Wave-Length Measurements in Spectra from 5600 A to 9600 A,” Bulletin of the Bureau of Standards 14 (1918): 371-395.

W. F. Meggers and Kievin Burns, “Notes on Standard Wave Lengths, Spectrographs, and Spectrum Tubes,” Scientific Papers of the Bureau of Standards 18 (1922): 185-199.

Walter F. Cannon, “Wadsworth Spectrograph,” Smithsonian Journal of History 1, #4 (1967): 73-74.

Location

Currently not on view