V. S. Kozlov and his Tsifrar-diagrammometer

In the late 19th century a military statistician and a pioneers of the Russian cooperative movement, Viktor Semyonovich Kozlov (1842–1920), designed and built a unique mechanical analog computing device he named “tsifrar-diagrammometer”. It was intended for operational visual presentation of numerical results of observations, calculations, experiments, etc. (tsifrar) and for calculating their statistical characteristics (diagrammometer). At the 1889 Paris Exposition this device that represented Russia was awarded the bronze medal. Drawing on the archival records and the materials from the Russian and European periodicals, the history of the inventor’s work on this device is reconstructed for the first time and some facts from his biography are described. The authors also attempt to describe the design of the device and analyze the mechanism of its functioning. Since no sources contain a detailed description of the design with the diagrams, charts, etc. or the mechanism of its functioning while available information is often contradictory, the authors present their own version of the device’s description and operation. The tsifrar-diagrammometer aroused much interest among the most prominent Russian and French scientists of the time, including P. L. Chebyshev, D. I. Mendeleev, E. Lucas, and many others. They viewed Kozlov’s device as a forerunner of a future universal instrument for numerical data analysis and for discovering new laws of nature. The appraisals of the device by the contemporaries are also given and analyzed in the article.