Hatfield's Adder

On 26th September, 1854, Aaron L. Hatfield of Lewisburg, Pennsylvania, was granted a patent No 11726 for machine for adding numbers. It seems the Hatfields was a huge and communicative Jewish family, because another Hatfield, Jehu, from Glens Falls, New York, has patented a similar device—Machine for calculating interest in 1844 (patent No 3574). In contrast with Jehu's machine however, Aaron's was much clever and was produced for some years (see the lower photo).

Hatfield's machine for adding numbers (© Jay Goldman, http://www.jmgoldman.com)

The device (see the lower drawing from the patent) consists of a series of circular metallic disks having numbers stamped thereon, so arranged, in connection with springs, that by alternative movement of a lever, any number of figures, from 1 to 10000 or more, may be correctly and easily added together before the eye.

The patent drawing of Hatfield's Adder