Physicist and surveyor (1806–1867) who helped engineer coastal fortifications and conducted a detailed survey of the entire east coast. Also the great-grandson of Benjamin Franklin. ALS signed “A. D. Bache,” one page, 4.75 x 8, June 26, 1855. Letter of introduction to meteorologist Ebenezer Meriam. In full: “I have the pleasure to introduce you to my friend Major J. G. Floyd who desires to procure some information in regard to exploding a number of blasts under water by galvanism. It has occurred to me that you can inform him who prepared the canister wires & batteries for M. Maillefert.” In fine condition, with a mild uniform shade of toning and scattered ink spots. Maillefert was an expert in removing rocks from riverbeds via underwater blasting, and would put his knowledge to military use during the Civil War, developing torpedoes for the Union’s naval forces. RR Auction COA.