Circular multiplication machine

The inventor of this calculating machine, the Hungarian Jewish doctor David Roth, immigrated to France, where he practised homeopathy for thirty years, treating wealthy Parisian patients. From 1841 onwards he registered several inventor’s patents for calculating machines. Alongside inventors such as Thomas de Colmar and Timoléon Maurel, he devised several innovations catering for the needs of the then-expanding sectors of trade, banking and insurance. During a stay in London in August 1841, he met Charles Babbage who told him about his work on his renowned ‘difference engine’. Whereas Pascal’s machine transmits the carry digit simultaneously to all the wheels, Roth’s mechanisms are based on the principle of their successive transmission: unlike the Pascaline, the number of wheels and therefore the size of numbers is no longer limited by the user’s manual strength.