Autographed letter signed, regarding the installation of a propeller in the steamboat "Experiment" in 1845 -- a time when the propeller was just being introduced. In part: "...Resolved, That Messrs. Betts & Lloyd, of Wilmington, be permitted to place a New Engine, boiler, and propeller in the steamboat 'Experiment', without being restricted to the weight of two tons..." 1 page, 4to, 9.75 x 7.5 inches, with an addendum on verso by Lloyd and Betts, engineers concerned in the matter. Address, wax seal, and postmarks on verso. Philadelphia, June 7, 1845. Several folds; very good condition.