Adders - Circular Adders
On some adders, numbers were represented along an arc of a circle. People used their fingers or a stylus to enter numbers. On a few of these instruments, a mechanism allowed one to carry a single digit. These objects are described here as adders with carry. They blur the line between adders and adding machines.
"Adders - Circular Adders" showing 1 items.
- 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 July 26, 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, July 26, 1888.
- date made
- Hart, William
- Scovill Manufacturing Company
- ID Number
- accession number
- catalog number
- Data Source
- National Museum of American History, Kenneth E. Behring Center