During all this period, though constant accessions were made to the knowledge of the coast by means of commercial adventure, the interior of the continent, from the Mississippi to the ocean, remained unknown. The intercourse of the people of the United States with the native tribes was restricted by several causes. One was the possession of Louisiana by the Spaniards; another, the retention by the British of several important posts south of the Great Lakes, within the acknowledged territory of the Union. At length, by the treaty of 1794 between Great Britain and the United States, those posts were given up to the Americans; and by treaty with France, in 1803, Louisiana, which had come into possession of that power in 1800, was ceded to the United States. From this period, the Government and people of the United States ceased to be indifferent to the immense and important region whose destinies were committed to them; and the ensuing narrative will relate the first attempt made by national authority to occupy and explore the country. CHAPTER II. LEWIS AND CLARKE. In the year 1786, John Ledyard of Connecticut, who had been with Capt. Cook in his voyage of discovery to the north-west coast of America in 1776-1780, was in Paris, endeavoring to engage a mercantile company in the fur-trade of that coast. He had seen, as he thought, unequalled opportunities for lucrative traffic in the exchange of the furs of that country for the silks and teas of China. But his representations were listened to with incredulity by the cautious merchants of Europe, and he found it impossible to interest any so far as to induce them to fit out an expedition for the object proposed.