 In 1803 Dunbar, with others, established the "Mississippi Society for the Acquirement and Dissemination of Useful Knowledge".After returning from the expeditions, and until his death in 1810, he devoted himself to scientific inquiry, gathering a significant collection of data on Indian vocabulary, as well as using chemical analysis in geology, seasonal river levels, fossils, astronomical phenomena, and utilizing a method of finding longitude by astronomical means.On March 13, 1804, Thomas Jefferson (who by then was President) wrote to Dunbar, charging him with the task of assembling the first scientific expedition into the lower Louisiana Purchase.