Monday, 12.  This morning as soon as it was light captain Lewis sent Drewyer to reconnoitre if possible the route of the Indians:  in about an hour and a half he returned, after following the tracks of the horse which we had lost yesterday to the mountains, where they ascended and were no longer visible.  Captain Lewis now decided on making the circuit along the foot of the mountains which formed the cove, expecting by that means to find a road across them, and accordingly sent Drewyer on one side, and Shields on the other.  In this way they crossed four small rivulets near each other, on which were some bowers or conical lodges of willow brush, which seemed to have been made recently.  From the manner in which the ground in the neighbourhood was torn up the Indians appeared to have been gathering roots; but captain Lewis could not discover what particular plant they were searching for, nor could he find any fresh track, till at the distance of four miles from his camp he met a large plain Indian road which came into the cove from the northeast, and wound along the foot of the mountains to the southwest, approaching obliquely the main stream he had left yesterday.  Down this road he now went towards the southwest:  at the distance of five miles it crossed a large run or creek, which is a principal branch of the main stream into which it falls, just above the high cliffs or gates observed yesterday, and which they now saw below them:  here they halted and breakfasted on the last of the deer, keeping a small piece of pork in reserve against accident:  they then continued through the low bottom along the main stream near the foot of the mountains on their right.  For the first five miles the valley continues towards the southwest from two to three miles in width; then the main stream, which had received two small branches from the left in the valley, turns abruptly to the west through a narrow bottom between the mountains.  The road was still plain, and as it led them directly on towards the mountain the stream gradually became smaller, till after going two miles it had so greatly diminished in width that one of the men in a fit of enthusiasm, with one foot on each side of the river, thanked God that he had lived to bestride the Missouri.  As they went along their hopes of soon seeing the waters of the Columbia arose almost to painful anxiety, when after four miles from the last abrupt turn of the river, they reached a small gap formed by the high mountains which recede on each side, leaving room for the Indian road.  From the foot of one of the lowest of these mountains, which rises with a gentle ascent of about half a mile, issues the remotest water of the Missouri.  They had now reached the hidden sources of that river, which had never yet been seen by civilized man; and as they quenched their thirst at the chaste and icy fountain—­as they sat down by the brink of that little rivulet, which yielded its distant and modest tribute to the parent ocean,