Juri Diakov

Around 1874, the Russian military engineer from Sankt Peterburg, captain Juri I. Diakov (Юрiй И. Дьяковъ), devised a simple row adder, one of many adding devices based on Abaque Rhabdologique of Claude Perrault. However, unlike the abacus of Perrault, the device of Diakov used endless bands, moved during the calculations repeatedly in one or another direction.

This simple and cheap device, called новаго рода счёты (New Type of Abacus), went into production in the late 1870s (see the lower image of a device from the 1880s). It is believed that Diakov was the inventor of several interesting calculating devices, which were granted a medal at the 1878 Exposition Universelle in Paris.

The abacus of Juri Diakov was a finger-operated calculating (adding and subtracting) device (dimensions 33 x 31 x 3 cm) with a carry indication. Carry needs to be enforced manually, as a black field indicates carry needs to be added on the next position. (Thank you Walter Szrek).

On 16 September 1880, Juri Diakov applied to the Russian Department of Trade and Manufacture for a 3-years (later in 1881 prolonged for 10 years) privilege (привилегия, i.e. patent) for the device. The privilege №8937 was granted on 16 November 1881. It seems the device achieved considerable market success until 1881 because the state tax for the privilege was quite big—450 rubles.

In the patent application (see the Privilege of Diakov) the device, named here “new type abacus” (новаго рода счеты), (see the lower patent drawing) was described as:
…new type abacus, using endless bands, moved during the calculations repeatedly in one direction. As a matter of fact, the essence of the device is a circular, unlimited movement, in one or another direction…

The principle of Diakov’s abacus will be further improved some ten years later in the Ribbon Adder of Charles Henry Webb, and later in several other adding devices like the popular Basset Adder from the beginning of the 20^th century.