Reducing Arc

Description:

William T. Rhodes (1898-1961) invented the reducing arc while conducting a topographical survey through the rugged terrain along the Merced River in California, in preparation for the All Year Highway to the west entrance of Yosemite National Park. When his design proved practicable, Rhodes submitted a patent application and convinced Lietz to manufacture the device in exchange for royalties.

The first advertisements appeared in 1928, and Rhodes received a patent in 1930. The Rhodes reducing arc was soon popular, especially with highway engineers. Lietz still had some in stock in the late 1980s. The inscription on this example reads "RHODES REDUCING ARC MFD. BY The A. LIETZ CO. SAN FRANCISCO, U.S.A. PATENTED NO. 1,785,284 SERIAL No. 18296."

The Rhodes reducing arc consists of a semicircle attached to a vertical pole, with a sighting tube on the straight edge. With it, a surveyor can take a sight on a vertical range pole, use a tape to measure the slope distance to the pole, and read the horizontal and vertical distances on the gridded half of the arc.

Ref: Doug Morin, "William T. Rhodes and His Reducing Arc," P.O.B. (May 1996): 60-64.

A. Lietz, Engineering, Surveying, Mining and Nautical Instruments (San Francisco, 1928), pp.122-123.

Maker: A. Lietz Company

Location: Currently not on view

See more items in: Medicine and Science: Physical Sciences, Surveying and Geodesy, Measuring & Mapping

Exhibition:

Exhibition Location:

Related Publication: P.O.B., A. Lietz. Engineering, Surveying, Mining and Nautical Instruments

Credit Line: Michael Baker, Jr., Inc.

Data Source: National Museum of American History

Id Number: 1997.0290.07Accession Number: 1997.0290Catalog Number: 1997.0290.07

Object Name: reducing arc

Measurements: overall: 15 in x 21 in x 2 1/2 in; 38.1 cm x 53.34 cm x 6.35 cm

Guid: http://n2t.net/ark:/65665/ng49ca746a8-862f-704b-e053-15f76fa0b4fa

Record Id: nmah_997339

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