10. In July of 1804 Commodore Preble arrived at Tripoli and began a siege. The town was bombarded, and several Moorish vessels were destroyed. In the mean time, William Eaton, the American consul at Tunis, had organized a force, and was marching overland to Tripoli. Hamet, who was the rightful sovereign of Tripoli, was cooperating with Eaton in an effort to recover his kingdom. Yusef, the Tripolitan emperor, made overtures for peace. His offers were accepted, and a treaty was concluded on the 4th of June, 1805. [Sidenote: =Schemes of Aaron Burr.=] 11. In 1804 the country was shocked by the intelligence that Vice-president Burr had killed Alexander Hamilton in a duel. As his term of office drew to a close, Burr foresaw that he would not be renominated. In 1803 he became a candidate for governor of New York; but Hamilton's influence in that State prevented his election. Burr thereupon sought a quarrel with Hamilton, challenged him, met him at Weehawken on the morning of the 11th of July, and deliberately murdered him. Thus the brightest intellect in America was put out in darkness. 12. After the death of Hamilton, Burr fled to the South. At the opening of the next session of Congress he returned to preside over the Senate. Then he took up his residence with an Englishman named Blennerhassett, who had built a mansion on an island in the Ohio, near the mouth of the Muskingum. Here Burr made a treasonable scheme to raise a military force, invade Mexico, detach the Southwestern States from the Union, and overthrow the government of the United States. But his purposes were suspected. The military preparations at Blennerhassett's Island were broken up. Burr was arrested in Alabama and taken to Richmond to be tried for treason. Chief-justice Marshall presided at the trial, and Burr conducted his own defence. The verdict was, "Not guilty--_for want of sufficient proof_." Burr afterward practiced law in New York, lived to old age, and died in poverty. [Sidenote: =Lewis and Clarke's Expedition.=] 13. In the autumn of 1804 Jefferson was reelected. For Vice-president, George Clinton of New York was chosen in place of Burr. In the next year a part of the Northwest Territory was organized under the name of MICHIGAN. In the same spring, Captains Lewis and Clarke set out from the falls of the Missouri River with thirty-five soldiers and hunters to explore Oregon. For two years, through forests of gigantic pines, and along the banks of unknown rivers, did they continue their explorations. After wandering among unheard-of tribes of savages, and traversing a route of six thousand miles, the adventurers, with the loss of but one man, returned to civilization. [Illustration: Lewis and Clarke's Expedition.]