Improved Calculator by Conkey And Loomis

This instrument consists of 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 inner 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 smaller arm advances one digit, indicating hundreds. Hundreds apparently cannot be entered directly. The adder is painted black on the reverse side and has a support attached to the back so that it sits at an angle. A green paper label glued to the back gives directions for use.
Census records list two men, one of whom may have been Alonzo Johnson, the co-inventor of this device. Both were machinists. Alonzo Johnson (no middle initial) was born 12 February 1828 in Bangor, Maine, the son of Louisa Underwood and Dolliver Johnson. Dolliver Johnson, a railroad engineer, became a superintendent of locomotive power on the Fitchburg Railroad in Massachusetts and then was associated with the Illinois Central in Illinois. His son Alonzo Johnson married in about 1850, and lived in Springfield, Massachusetts, with his wife, Sarah, and their children from at least 1870 through 1900. Census records also list Alonzo H. Johnson, born about 1828 in Connecticut, who was living with his wife, Hannah, also in Springfield, in 1870, 1880 and 1900.
One of these Alonzo Johnsons took out eight patents. The first two were 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), #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).
James A. Loomis, the co-inventor of this device, is probably the James Loomis listed in United States Census records for 1860, 1870, and 1880 as a resident of Springfield, Massachusetts. He is listed in 1860 as a 45-year-old wheelright, in 1870 as a 57-year-old carriage maker born in Massachusetts, and in 1880 as a 67-year-old retired carriage maker.
The “Conkey” referred to in the name of the device may be Henry Conkey, who is listed as a 27-year-old machinist in Enfield, Massachusetts, in the 1860 Census and as a 35-year-old machinist in Springfield, Massachusetts, in the 1870 U.S. Census.
References: James A. Loomis and Alonzo Johnson, “Improvement in Calculating Machines,” U.S. Patent 73732, 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
Conkey & Loomis
Physical Description
paper (overall material)
brass (overall material)
steel (overall material)
overall: 4.3 cm x 18 cm x 18 cm; 1 11/16 in x 7 3/32 in x 7 3/32 in
place made
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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