The instrument consists of three concentric brass discs, a brass marker, a steel stop, and a wooden handle (instrument must be removed from box to find handle). Each brass disc has the numbers from 0 to 99 stamped around the edge. The two inner discs both have a circle of 100 holes just outside the numbers. The inner holes are used to add the last two digits of a number by rotation. Any hundreds value in the sum carries to the second set of holes, which are used to add hundreds and thousands places.
The machine is in a cylindrical wooden case with cover.
According to the Kirksville [Missouri] Democrat for August 2, 1888, by then Hart had sold 3500 of these devices and “he lately ordered one thousand more.”
References: U.S. Patent #199289
P. Kidwell, "Adders Made and Used in the United States," Rittenhouse, 1994, 8:78-96.
Kirksville [Missouri] Democrat, August 2, 1888.
Our collection database is a work in progress. We may update this record based on further research and review. Learn more about our approach to sharing our collection online.
If you would like to know how you can use content on this page, see the Smithsonian's Terms of Use. If you need to request an image for publication or other use, please visit Rights and Reproductions.