Our road the next day was through a continued and dense field of artemisia, which now entirely covered the country in such a luxuriant growth that it was difficult and laborious for a man on foot to force his way through, and nearly impracticable for our light carriages. The region through which we were traveling was a high plateau, constituting the dividing ridge between the waters of the Atlantic and Pacific oceans, and extending to a considerable distance southward, from the neighborhood of the Table rock, at the southern side of the South Pass. Though broken up into rugged and rocky hills of a dry and barren nature, it has nothing of a mountainous character; the small streams which occasionally occur belonging neither to the Platte nor the Colorado, but losing themselves either in the sand or in small lakes. From an eminence, in the afternoon, a mountainous range became visible in the north, in which were recognised some rocky peaks belonging to the range of the Sweet Water valley; and, determining to abandon any further attempt to struggle through this almost impracticable country, we turned our course directly north, towards a pass in the valley of the Sweet Water river. A shaft of the gun-carriage was broken during the afternoon, causing a considerable delay; and it was late in an unpleasant evening before we succeeded in finding a very poor encampment, where there was a little water in a deep trench of a creek, and some scanty grass among the shrubs. All the game here consisted of a few straggling buffalo bulls, and during the day there had been but very little grass, except in some green spots where it had collected around springs or shallow lakes. Within fifty miles of the Sweet Water, the country changed into a vast saline plain, in many places extremely level, occasionally resembling the flat sandy beds of shallow lakes. Here the vegetation consisted of a shrubby growth, among which were several varieties of chenopodiaceous plants; but the characteristic shrub was Fremontia vermicularis, with smaller saline shrubs growing with singular luxuriance, and in many places holding exclusive possession of the ground.
On the evening of the 8th we encamped on one of these fresh-water lakes, which the traveler considers himself fortunate to find; and the next day, in latitude, by observation, 42° 20' 06", halted to noon immediately at the foot of the southern side of the range which walls in the Sweet Water valley, on the head of a small tributary to that river.
Continuing in the afternoon our course down the stream, which here cuts directly through the ridge, forming a very practicable pass, we entered the valley; and, after a march of about nine miles, encamped on our familiar river, endeared to us by the acquaintance of the previous expedition--the night having already closed in with a cold rain-storm. Our camp was about twenty miles above the Devil's gate, which we had been able to see in coming down the plain; and, in the course of the night, the clouds broke away around Jupiter for a short time; during which we obtained an emersion of the first satellite, the result of which agreed very nearly with the chronometer, giving for the mean longitude 107° 50' 07"; elevation above the sea 6,040 feet; and distance from St. Vrain's fort, by the road we had Just traveled, 315 miles.
Here passes the road to Oregon; and the broad smooth highway, where the numerous heavy wagons of the emigrants had entirely beaten and crushed the artemisia, was a happy exchange to our poor animals, for the sharp rocks and tough shrubs among which they had been toiling so long; and we moved up the valley rapidly and pleasantly. With very little deviation from our route of the preceding year, we continued up the valley; and on the evening of the 12th encamped on the Sweet Water, at a point where the road turns off to cross to the plains of Green river. The increased coolness of the weather indicated that we had attained a greater elevation, which the barometer here placed at 7,220 feet; and during the night water froze in the lodge.
The morning of the 13th was clear and cold, there being a white-frost, and the thermometer, a little before sunrise, standing at 26.5°. Leaving this encampment, (our last on the waters which flow towards the rising sun,) we took our way along the upland, towards the dividing ridge which separates the Atlantic from the Pacific waters, and crossed it by a road some miles further south than the one we had followed on our return in 1842. We crossed very near the Table mountain, at the southern extremity of the South Pass, which is near twenty miles in width, and already traversed by several different roads. Selecting, as well as I could, in the scarcely distinguishable ascent, what might be considered the dividing ridge in this remarkable depression in the mountain, I took a barometrical observation, which gave 7,490 feet for the elevation above the Gulf of Mexico. You will remember that, in my report of 1842, I estimated the elevation of this pass at about 7,000 feet; a correct observation with a good barometer enables me to give it with more precision. Its importance, as the great gate through which commerce and traveling may hereafter pass between the valley of the Mississippi and the North Pacific, justifies a precise notice of its locality and distance from leading points, in addition to this statement of its elevation. As stated in the report of 1842, its latitude, at the point where we crossed, is 42° 24' 32"; its longitude 109° 26' 00"; its distance from the mouth of the Kansas, by the common traveling route, 962 miles; from the mouth of the Great Platte, along the valley of that river, according to our survey of 1842, 882 miles; and its distance from St. Louis about 400 miles more by the Kansas, and about 700 by the Great Platte route; these additions being steamboat conveyance in both instances. From this pass to the mouth of the Oregon is about 1,400 miles by the common traveling route; so that under a general point of view, it may be assumed to be about half-way between the Mississippi and the Pacific ocean, on the common traveling route. Following a hollow of slight and easy descent, in which was very soon formed a little tributary to the Gulf of California, (for the waters which flow west from the South Pass go to this gulf,) we made our usual halt four miles from the pass, in latitude, by observation, 42° 19' 53". Entering here the valley of Green river--the great Colorado of the West-- and inclining very much to the southward along the streams which form the Sandy river, the road led for several days over dry and level uninteresting plains; to which a low scrubby growth of artemisia gave a uniform dull grayish color; and on the evening of the 15th we encamped in the Mexican territory, on the left bank of Green river, 69 miles from the South Pass, in longitude 110° 05' 05", and latitude 41° 53' 54", distant 1,031 miles from the mouth of the Kansas. This is the emigrant road to Oregon, which bears much to the southward, to avoid the mountains about the western heads of Green river--the Rio Verde of the Spaniards.
16th.--Crossing the river, here about 400 feet wide, by a very good ford, we continued to descend for seven or eight miles on a pleasant road along the right bank of the stream, of which the islands and shores are handsomely timbered with cottonwood. The refreshing appearance of the broad river, with its timbered shores and green wooded islands, in contrast to its dry and sandy plains, probably obtained for it the name of Green river, which was bestowed on it by the Spaniards who first came into this country to trade some 25 years ago. It was then familiarly known as the Seeds-ke-dee-agie, or Prairie Hen (tetrao urophasianus) river; a name which it received from the Crows, to whom its upper waters belong, and on which this bird is still very abundant. By the Shoshonee and Utah Indians, to whom belongs, for a considerable distance below, the country where we were now traveling, it was called the Bitter Root river, from a great abundance in its valley of a plant which affords them one of their favorite roots. Lower down, from Brown's hole to the southward, the river runs through lofty chasms, walled in by precipices of red rock; and even among the wilder tribes which inhabit that portion of its course, I have heard it called by Indian refugees from the California settlements the Rio Colorado. We halted to noon at the upper end of a large bottom, near some old houses, which had been a trading post, in lat. 41° 46' 54". At this place the elevation of the river above the sea is 6,230 feet. That of Lewis's fork of the Columbia at Fort Hall is, according to our subsequent observations, 4,500 feet. The descent of each stream is rapid, but that of the Colorado is but little known, and that little derived from vague report. Three hundred miles of its lower part, as it approaches the Gulf of California, is reported to be smooth and tranquil; but its upper part is manifestly broken into many falls and rapids. From many descriptions of trappers, it is probable that in its foaming course among its lofty precipices it presents many scenes of wild grandeur; and though offering many temptations, and often discussed, no trappers have been found bold enough to undertake a voyage which has so certain a prospect of a fatal termination. The Indians have strange stories of beautiful valleys abounding with beaver, shut up among inaccessible walls of rock in the lower course of the river; and to which the neighboring Indians, in their occasional wars with the Spaniards and among themselves, drive their herds of cattle and flocks of sheep, leaving them to pasture in perfect security.
The road here leaves the river, which bends considerably to the east; and in the afternoon we resumed our westerly course, passing over a somewhat high and broken country; and about sunset, after a day's travel of 26 miles, reached Black's fork of the Green river--a shallow stream, with a somewhat sluggish current, about 120 feet wide, timbered principally with willow, and here and there an occasional large tree. At three in the morning I obtained an observation of an emersion of the first satellite of Jupiter, with other observations. The heavy wagons have so completely pulverized the soil, that clouds of fine light dust are raised by the slightest wind, making the road sometimes very disagreeable.
17th.--Leaving our encampment at six in the morning, we traveled along the bottom, which is about two miles wide, bordered by low hills, in which the strata contained handsome and very distinct vegetable fossils. In a gully a short distance farther up the river, and underlying these, was exposed a stratum of an impure or argillaceous limestone. Crossing on the way Black's fork, where it is one foot deep and forty wide, with clear water and a pebbly bed, in nine miles we reached Ham's fork, a tributary to the former stream, having now about sixty feet breadth, and a few inches depth of water. It is wooded with thickets of red willow, and in the bottom is a tolerably strong growth of grass. The road here makes a traverse of twelve miles across a bend of the river. Passing in the way some remarkable hills, two or three hundred feet high, with frequent and nearly vertical escarpments of a green stone, consisting of an argillaceous carbonate of lime, alternating with strata of an iron-brown limestone, and worked into picturesque forms by wind and rain, at two in the afternoon we reached the river again, having made to-day 21 miles. Since crossing the great dividing ridge of the Rocky mountains, plants have been very few in variety, the country being covered principally with artemisia.
18th.--We passed on the road, this morning, the grave of one of the emigrants, being the second we had seen since falling into their trail; and halted to noon on the river, a short distance above.
The Shoshonee woman took leave of us here, expecting to find some of her relations at Bridger's fort, which is only a mile or two distant, on a fork of this stream. In the evening we encamped on a salt creek, about fifteen feet wide, having to-day traveled 32 miles.