I left St. Josephs for the Indian country lying west of the Missouri river, through which I was to pass on my way to Oregon, with a train of emigrants for that place, on the 25th of April, 1848, with a view of reaching Oregon before the inclemencies of winter should overtake me, under as favorable auspices as the nature of the case would allow. The Indian country is a wild, uncultivated tract, and almost destitute of inhabitants. It has, however, a few scattering tribes of Indians, though few indeed and far between. This country is what is calld a prairie country or natural meadow, with very little timber except along the water-courses. It is a continuation of the great valley of the Mississippi westward along the tributaries to the Rocky mountains, where the waters of the continent divide and run westward into the Pacific ocean. A prairie may be an alluvial country, and it may be tertiary. The one here spoken of is alluvial. At a remote period, the timber and loose material of the country, as well as all prairie districts, were fired by its inhabitants or by lightning, and this continued for ages will destroy the timber and leave its soil to be clothd only by the grasses, an inferior but oftentimes resplendent robe. The traveler soon after leaving St. Josephs, westward sees prairie in all stages of formation, from the dense forest to an entire prairie. This, with the dense forests of young timber eastward, where the white man has forbidden the practice of firing prairies, seems to be a convincing proof of the aforementioned mode of prairie formation. It has been noticed in the State of Illinois, and some other places, where the plowman is permitted to glide his plow smoothly over the beautiful landscape, that there is an exceedingly fine scouring material lying near the surface of the soil, so that steel mold boards, on a very short use of them, are seen to present a polishd surface, on drawing them from the soil.—Ages of constant burning of the prairie grasses must necessarily produce a great amount of very fine coal dust and ashes, which, by the beating rains from year to year, would cause it to mingle with the earth to the depth of several inches. Such is the probable cause of the scouring material of these plains. On passing over the country from St. Josephs to the dividing ridge of the continent, along the emigrant route to Oregon, the traveler accustomd only to fertile districts, is greatly surprised at finding so great a portion of the continent an almost barren waste. From St. Josephs to the Platt river, a distance of 250 miles, is most of the way a country of soil and fertility. On arriving at the Platt river, a beautifully flat country presents itself, where nature, it would seem, has but an easy task to burden the ground with excessive vegetation, but behold a country of extensive bottom lands, of feeble soil much of the way, and still more feeble at the distance, among the bluffs and rolling country.