WEST OF THE ROCKY MOUNTAINS.We have been politely favored by Gen. Ci,a**v Superintendent of Indian Affair*, with the perusal of t a letter, written by Jedediah 8 Smith, who has been/ for several years engaged in hunting and trapping in the Upper Missouri, and who has visited that extensive barren country on the West, not here oforo explored. From this letter, written in a plain styl** we extract the following, which, we trust, will be found interesting to our readers.[ Missouri Republican.My situation has enabled me to collect information respecting a country which has been, measurably, veiled in obscurity, and unknown to the citizens of the United Stales. I allude to the country Soutti West of the Great Salt Lake,and West of the Rockv mountains.About the 22d of August, 1826, I left the great Salt Lake, accompanied with a party of fifteen men, for the purpose ofexploring the country to the South West, which was then entirely unknown tome., and of which I could obtain no satisfactory information, from the Indians who inhabit the country on its North Last borders. M y general course on leaving the; Lake, was 8. W. and W. passing the Little Uta Lake, and ascending Ashley’s River, which empties into it, where we* found a nation of Indians, calling themselves Svmpufclu who were friendly disposed towards us. Alter leaving the Little Uta Lake, I found no further sign of huff,do—there were, however. a few of the Antelope and Mountain Shoes, and all abundance ol Ulalt; k J ailed Hares. Leaving Ashley’s River, I passed over a range of mountains, S. K. and N. W. and struck a river, running 8. W. which I named Adams River, in compliment to our . President. The water of this river is of a muddy cast, and somewhat brackish. T:,e country is moun-turnons to the Last, and -m the West arc detached rocky hills and sandv plains. Passing down this river some distance, I fell in with a nation of Indians, calling themselves Pa Utches. 'These Indian-, as well as the Sumpateh, wear robes made of rabbit skins; they raise corn and pumpkins, on which they principally subsist—except a few hares, very little game of any description is to be found. About ten days march further down, the river turns to th» S Fi. where, on the 8. W. of it. there is ft remarkable cave, the entrance to which is about ten or fifteen feet high ; and five or six feet in width ; after descending about fifteen fret, opens into a large and spacious room, with the roofr, walls, and floor, of solid rock salt, (a piece of which 1 send you, withn.k.nd•aln*Idpdleetns1.yasisryasane»rs,•c-ornit