Locke Adder


The first American-made adder to enjoy modest commercial success was developed by Clarence E. Locke (1865-1945). A native of Edgerton, Wisconsin, he graduated from Cornell College in Mt. Vernon, Iowa, in 1892. Locke worked for a time as a civil engineer in Minnesota, and then joined his father operating a lumber yard in Kensett, Iowa.

This version of the device has a metal base with grooves for nine sliding metal rods that move crosswise. Each rod represents a digit of a number being added. Protruding knobs on the rods represent different numerals. The rods are held in place by bronze-colored metal covers that extend over the right and left thirds of the instrument. When the device is in zero position, all the rods are in their rightmost position.

Numbers are entered by sliding rods to the left, and the result appears in numbers immediately to the left of the cover on the right. The rods are color-coded to distinguish units of money. They lock when depressed, so that they will not slide if the instrument is tilted. The locking mechanism, the color-coded rods, and the oval shape of the knobs on the rods are all improvements featured in Locke’s second calculating machine patent, taken out in 1905. There is no carry mechanism. The base of is covered with green cloth.

The instrument is marked on the right cover: C. E. LOCKE (/) MFG. Co. It also is marked: KENSETT, IOWA. [/] U.S.A. It is marked on the left cover: THE (/) LOCKE (/) ADDER. It also is marked: PATENTED DEC. 24. 1901 (/) JAN. 3 1905. This example came to the Smithsonian from the collection of L. Leland Locke.

The instrument resembles MA.323619, but it has green rather than red cloth on the bottom and has no surrounding wooden box. Also compare to MA.321327.

References: C. E. Locke, “Calculating Machine,” U.S. Patent 689680, December 24, 1901.

C. E. Locke, “Calculating Machine,” U.S. Patent 779088, January 3, 1905.

Robert Otnes, “Sliding Bar Calculators,” ETCetera #11 (June 1990): pp. 6-8.

P. Kidwell, “Adders Made and Used in the United States,” Rittenhouse, 8, (1994): pp. 78-96.

Date Made: 1905

Maker: C. E. Locke Manufacturing Company

Location: Currently not on view

Place Made: United States: Iowa, Kensett

Subject: Mathematics


See more items in: Medicine and Science: Mathematics, Adder, Science & Mathematics


Exhibition Location:

Credit Line: Gift of L. Leland Locke

Data Source: National Museum of American History

Id Number: MA.155183.29Catalog Number: 155183.29Accession Number: 155183

Object Name: adder

Physical Description: felt (overall material)metal (overall material)Measurements: overall: 1.2 cm x 27.3 cm x 10.3 cm; 15/32 in x 10 3/4 in x 4 1/16 in

Guid: http://n2t.net/ark:/65665/ng49ca746a5-12c2-704b-e053-15f76fa0b4fa

Record Id: nmah_690241

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