An account of expeditions to the sources of the Mississippi and through the western parts of Louisiana, to the sources of the Arkansaw, Kans, La Platte, and Pierre Jaun, rivers performed by order of the government of the United States during the years 1805, 1806, and 1807 : and tour through the interior parts of New Spain, when conducted through the interior parts of the captain-general, in the year 1807 /