The Dunbar‐Hunter Expedition (1804–1805): Early Analyses of Spring Waters in the Louisiana Purchase

Abstract

Introduction In the years folowing the Louisiana Purchase Treaty with France in 1803, U.S. President Thomas Jefferson commissioned four expeditions to explore the new territory. Best known of these, of course, was the Lewis and Clark expedition of 1804–1806 across the northern margin of the purchase. However, there was also the Pike expedition of 1806–1807 into the Rocky Mountains and the Southwest, and the abbreviated Freeman-Custis expedition up the Red River in 1806, which was blocked by the Spanish just west of what is now the Texas-Arkansas border. Of some interest in the history of hydrogeology is the second expedition Jefferson commissioned, the Dunbar-Hunter expedition of 1804–1805 up the Ouachita (Washita) River in what is now Louisiana and Arkansas to the hot springs of central Arkansas. The daily journals and final reports of William Dunbar and George Hunter provided the first scientific description of the Ouachita River and surrounding area in English. In addition, Hunter made water quality determinations at some salt seeps and hot springs and speculated on the source of heat for the latter. Dunbar, in turn, attempted to determine the total rate of discharge of the hot springs and also wrote down his thoughts on their origin. The purpose of this note is to describe some of the field techniques used by Dunbar and Hunter at the time of their expedition and to analyze their scientific observations and thoughts from a modern perspective. The biographical information on the two explorers contained in this note is based on material in McDermott (1963) and Berry et al. (2006). The interpretations of Dunbar and Hunter’s findings are those of this author.