Fearnley's patent Universal calculator, circular slide rule with cardboard scale in fitted mahogany case, unsigned, British,1880-1900. Used at the University Observatory, Cambridge, at Madingley Road, Cambridge, England.
Fearnley's patent Universal calculator, circular slide rule with cardboard scale in fitted mahogany case, unsigned, British,1880-1900. Used at the University Observatory, Cambridge, at Madingley Road, Cambridge, England.