Kummer Slide Adder (1847)

"Apokin, Igor' Alekseevich. Maistrov, Leonid Efimovich, Razvitie vychislitel'nykh mashin (US Library of Congress translitteration, freely translated: Development of calculating machines and computers). 1974. 398 p., [1] fold. leaf : ill. ; 22 cm.

The upper part is for addition and lower part for subtraction. The device has been designed for Russian currency, because of the units Ryb (ruble), K (kopek) and evidently a quarter of a kopek coin has also been available. According to the book Kummer was a music teacher in St. Petersburg, but any other information, for example his first name is not given."


Source: Timo Leipala

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