In the years 1819 and 1820, several persons, well qualified for the undertaking by their science, spirit, and enterprize, accompanied by riflemen, hunters, and assistants, were sent out by the government of the United States, for the purpose of gaining a more full and accurate knowledge of the chain of the Rocky Mountains, and of the rivers, winch, rising there, flowed into the Mississippi.  After passing through a great extent and variety of country, and gaining some curious information respecting various Indian tribes, especially of those who inhabit the upper course of the Missouri, they reached the Mountains:  these and the adjacent districts they carefully examined.  They next separated, one party going towards the Red River, and the other descending the Arkansa.  The former party were misled and misinformed by the Indians, so that they mistook and followed the Canadian River, instead of the Red River, till it joined the Arkansa.  They were, however, too exhausted to remedy their error.  The latter party were more successful.

The great outline of the coast, as well as of the greater portion of the vast continent of America, is now filled up.  In the northernmost parts of North America, the efforts of the British government to find a north-west passage, the spreading of the population of Canada, and the increasing importance of the fur trade, bid fair to add the details of this portion; the spread of the population of the United States towards the west, will as necessarily give the details of the middle portion; while, with respect to the most southern portions of North America, and the whole of South America, with the exception of the cold, bleak, and barren territory of Patagonia, the changes which have taken place, and are still in operation, in the political state of the Spanish and Portuguese provinces, must soon fill up the little that has been left unaccomplished by Humboldt, &c.

What portions, then, of Asia, America, and Africa, are still unknown?—­and what comparison, in point of extent and importance, do they bear to what was known to the ancients?  In Asia, the interior of the vast kingdom of China is very imperfectly known, as well as Daouria and other districts on the confines of the Chinese and Russian empires; central Asia in general, and all that extensive, populous, and fertile region which extends from the southern part of Malaya, nearly under the equator, in a northerly direction, to the fortieth degree of latitude, are still not explored, or but very partially so, by European travellers.  This region comprehends Aracan, Ava, Pegu, Siam, Tsiompa, and Cambodia.  The south and east coasts of Arabia still require to be more minutely and accurately surveyed.  In the eastern archipelago, Borneo, Celebes, and Papua, are scarcely known.  Though all these bear but a small proportion to the vast extent of Asia, yet some of them, especially the country to the north of the Malay peninsula, and the islands in the eastern archipelago, may justly be regarded as not inferior, in that importance which natural riches bestows, to any part of this quarter of the globe.