Rare boxwood rule patented by Sir Ganga Ram (1851-1927) for calculating strains on girders and made by Stanley Great Turnstile Holborn London. Scales for Bending strain in tons at any point corresponding to the product/product of bays or distances from each abutment/shearing strains in tons due to travelling load.
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.