The scientific members of the expedition had meanwhile assembled at Pittsburg, and on May 5, 1819, they began the descent of the Ohio in the steamer "Western Engineer."[6] Stephen Harriman Long, the chief of this party, was born at Hopkinton, New Hampshire, in 1764. After being graduated at Dartmouth (1809), and teaching for a few years, he entered the army (1814) as lieutenant in the corps of engineers. Until 1816 he was assistant professor of mathematics at West Point, being then transferred to the topographical engineers, with the brevet rank of major. Previous to the exploration which forms the subject of our text, he travelled extensively in the South-west, between the Arkansas and Red rivers, and his journals, although never published, ranked among the most useful sources of information for that region. Major Long's associates in the present undertaking were Major John Biddle, journalist of the party; Dr. William Baldwin, physician and botanist; Dr. Thomas Say, zoologist; Augustus Edward Jessup, geologist; T. R. Peale, assistant naturalist; Samuel Seymour, painter; and Lieutenant James D. Graham and Cadet William H. Swift, assistant topographers.[7] The "Western Engineer" arrived at St. Louis on the ninth of June, and proceeded again on the twenty-first, after the party had completed certain arrangements for their journey and examined the Indian mounds in the vicinity. The voyage up the Missouri was begun on the twenty-second, being marked by no more important incident than an occasional halt to repair the machinery or clean the boiler. Notwithstanding it drew but nineteen inches of water, the boat grounded twice on sand-bars within four miles of the Mississippi; but on the whole, it worked fairly well and gave comparatively little annoyance. At St. Charles, on June 27, the party was joined by Benjamin O'Fallon, agent for Indian affairs, and John Dougherty, his interpreter. Here Messrs. Say, Jessup, Peale, and Seymour left the boat and made a land excursion, rejoining the party at Loutre Island. At Franklin, then the uppermost town of any importance on the Missouri, a halt of several days was made; here Dr. Baldwin, who had been ill since the departure from Pittsburg, was left behind, his death occurring on the thirty-first of August. From Franklin a party under Dr. Say proceeded by land to Fort Osage, where they arrived on July 24, a week in advance of the boat. On the sixth of August Dr. Say left Fort Osage in command of a party bound for the principal village of the Kansa Indians, then situated near the site of the present village of Manhattan, Kansas. Arriving there on the twentieth, they were hospitably entertained for four days; but after their departure were set upon and robbed by a war party of Pawnee braves, and consequently forced to abandon further progress by land and return to the boat.