 When the textile business dried up, he began importing indigo, iron and sugar and sold salt to the Du Pont Company for the manufacture of munitions.He dedicated himself to the study of political economy and to the collection of financial and commercial statistics and exchanged correspondences with contemporary British economists such as McCulloch, Tooke, Villiers, Cobden who considered him an authority.He assisted Albert Gallatin in preparing an analysis of the impact of the tariff on free trade in 1831 and became an advocate of free trade.