Saturday 4.  This morning captain Lewis proceeded early, and after going southeast by east for four miles, reaching a bold running creek, twelve yards wide, with clear cold water, furnished apparently by four drains from the snowy mountains on the left; after passing this creek he changed his direction to southeast, and leaving the valley in which he had travelled for the last two days, entered another which bore east.  At the distance of three miles on this course he passed a handsome little river, about thirty yards wide, which winds through the valley:  the current is not rapid nor the water very clear, but it affords a considerable quantity of water, and appears as if it might be navigable for some miles.  The banks are low, and the bed formed of stone and gravel.  He now changed his route to southwest, and passing a high plain which separates the vallies, returned to the more southern or that which he had left:  in passing this he found a river about forty-five yards wide, the water of which has a whitish blue tinge, with a gentle current, and a gravelly bottom.  This he waded and found it waist deep.  He then continued down it, till at the distance of three quarters of a mile he saw the entrance of the small river he had just passed; as he went on two miles lower down, he found the mouth of the creek he had seen in the morning.  Proceeding further on three miles, he arrived at the junction of this river, with another which rises from the southwest, runs through the south valley about twelve miles before it forms its junction, where it is fifty yards wide:  we now found that our camp of last night was about a mile and a half above the entrance of this large river, on the right side.  This is a bold, rapid, clear stream, but its bed is so much obstructed by gravelly bars, and subdivided by islands, that the navigation must be very insecure, if not impracticable.  The other or middle stream, has about two thirds its quantity of water, and is more gentle, and may be safely navigated.  As far as it could be observed, its course was about southwest, but the opening of the valley induced him to believe that farther above it turned more towards the west.  Its water is more turbid and warmer than that of the other branch, whence it may be presumed to have its sources at a greater distance in the mountains, and to pass through a more open country.  Under this impression he left a note recommending to captain Clarke the middle fork, and then continued his course along the right side of the other, or more rapid branch.  After travelling twenty-three miles he near a place where the river leaves the valley and enters the mountain.  Here he encamped for the night.  The country he passed is like that of the rest of this valley, though there is more timber in this part on the rapid fork than there has been on the river in the same extent since we entered it; for on some parts of the valley the Indians seem to have destroyed a great proportion of the little timber there was, by setting fire to the bottoms.  He saw some antelopes, deer, cranes, geese and ducks of the two species common to this country, though the summer duck has ceased to appear, nor does it seem to be an inhabitant of this part of the river.