Patent Model for an Adder with Carry by Alonzo Johnson

This patent model for an adder has as its base two concentric brass discs, one rotating inside the other. The rim of the outer disc has the numbers from 0 to 99 engraved around its edge. The inner disc has 100 small holes marked evenly around its edge. These also are numbered 0 to 99. Two steel arms pivot at the center of the disc. The longer arm has a pin on the underside that fits into the holes and a small knob on the upper side so that it can be rotated. A protruding pin set at 0 in the outer circle stops the motion of this arm. It is used to add numbers up to 99.
When the total on the inner disc exceeds 99, the the smaller arm advances one digit, indicating hundreds. The number of hundreds entered appears in a window in a small disc that is on top of three relatively small gears concentric to the large discs. Hundreds apparently cannot be entered directly. The adder has a handle that projects from the center of the back.
Census records list two men who may have been Alonzo Johnson, the inventor of this device. Both were machinists. One Alonzo Johnson (no middle initial) was born 12 February 1828 in Bangor, Maine, the son of Louisa Underwood and Dolliver Johnson. Alonzo's father was a railroad engineer, then a superintendent of locomotive power on the Fitchburg Railroad and then associated with the Illinois Central. This Alonzo Johnson married in about 1850, and lived in Springfield with his wife Sarah and their children from at least 1870 through 1900. Census records also list an Alonzo H. Johnson, born about 1828 in Connecticut, who was living with his wife Hannah in Springfield in 1870, 1880 and 1900.
Alonzo Johnson of Springfield took out eight patents, the first two for calculating devices. These were #73732 (granted January 28, 1868, with James A. Loomis as co-inventor and Charles Gifford of Gardiner, Maine, as assignee), and #85229 (taken out December 22,1868, and assigned to Sylvester Bissell and Andrew West of Hartford). Later patents were for nut-locks (#188055, granted March 6, 1871), slitting lock nuts (#231492, granted August 24, 1880), a car-brake (#235152, granted December 7, 1880), a card-cutter (#241372, granted May 10, 1881), a sash-fastener (#255144, granted April 11, 1882), and a gumming device for envelope machines (#397798, granted February 12, 1889).
Compare to 1990.0318.01.
Reference: Alonzo Johnson, “Improvement in Calculating-Apparatus,” U.S. Patent 85,229, December 22, 1868.
P. Kidwell, "Adders Made and Used in the United States," Rittenhouse, 1994, 8:78-96.
Currently not on view
Object Name
adder with carry
date made
Johnson, Alonzo
Johnson, Alonzo
Physical Description
brass (overall material)
wood (overall material)
steel (overall material)
overall: 16.5 cm x 18.5 cm x 18.5 cm; 6 1/2 in x 7 9/32 in x 7 9/32 in
place made
United States: Massachusetts, Springfield
place patented
United States: Massachusetts, Springfield
ID Number
accession number
catalog number
Science & Mathematics
See more items in
Medicine and Science: Mathematics
Data Source
National Museum of American History, Kenneth E. Behring Center
Additional Media

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