To construct the first atomic bomb, Manhattan Project scientists required large amounts of copper to make conductors for electromagnets, but there was a shortage because of World War II. Since silver also conducts electricity well, the U.S. Treasury loaned them 14,700 tons of the precious metal from the reserve (worth $304 million), which was then shaped into suitable parts. After the war all the silver was melted down and returned, with less than 1 percent lost.