Mendenhall's Practical Calculator

<< >>
This patent model for an adder has a brass box with a rotating disc inset in the top. There are 100 small holes around the rim of the disc. Outside the disc, on the top of the box, is a circular ring numbered from 01 to 99, with a gap at 00. Outside of this are three rings of holes, with 100 holes in each ring. These holes are to be used to hold markers indicating digits carried when the disc makes full rotations. On the side of the box is a rotating multiplication table.
A. Mendenhall, who patented this adder, was undoubtedly Amos Mendenhall, who was born in Ohio in 1828 and raised in east central Indiana. His father, Hiram Mendenhall (1801-1852) was a miller and farmer by trade and a Quaker and abolitionist in belief. In 1844, Hiram Mendenhall, as a representative of the Randolph County Anti-Slavery Society, presented a petition to presidential candidate Henry Clay, urging him to free his slaves. Clay refused and publicly rebuked Mendenhall. Hiram Mendenhall went on to pool his property with others to form the Unionport commune of the Society for Universal Inquiry and Reform. This effort soon collapsed and Hiram and Amos went to California to recoup the family fortunes in the gold fields. They failed to do this, and Hiram died of cholera on shipboard en route home. Amos, his mother, and his siblings continued to live in Unionport, where Amos farmed and tinkered. In the 1880 census, his occupation is given as “manufacture.”
The “practical calculator” was Mendenhall's first patented invention. He took out patents for gold mining devices (#360713, granted April 5, 1887, and # 541912, granted June 11, 1895), a tricycle (#453151, granted May 26, 1891), and a bicycle (#740156, granted September 29, 1903).
References: Patent #67,786, August 13, 1867 (Munn Co., attorneys); Scientific American, vol. 17, August 31, 1867, p. 141.
U.S. Census records for 1860, 1880, 1900.
Thomas D. Hamm, God’s Government Begun: The Society for Universal Inquiry and Reform, 1842-1846, Bloomington: Indiana University Press, 1996.
Currently not on view
date made
Mendenhall, A.
Mendenhall, A.
place made
United States: Indiana, Cerro Gordo
place patented
United States: Indiana, Cerro Gordo
Physical Description
brass (overall material)
metal (overall material)
overall: 5.4 cm x 13 cm x 13.8 cm; 2 1/8 in x 5 1/8 in x 5 7/16 in
ID Number
accession number
catalog number
See more items in
Medicine and Science: Mathematics
Science & Mathematics
Data Source
National Museum of American History


Add a comment about this object