An example of Major General Hannyngton’s extended slide rule allowing for more accurate calculations. Made by Aston and Mander.
Ask the Dealer
Fletcher Wallis sells objects and books relating to the history of science, medicine and technology from his unit at Admiral Vernon Arcade Portobello Road. He publishes books through Vernier Press, including Antique Medicine Chests, and Corkscrew Patents from 1795. He has been dealing for thirty five years.