and the valley widens to the extent of several miles.  The river now becomes crowded with islands of which we passed ten in the next thirteen and three quarter miles, then at the distance of eighteen miles we encamped on the left shore near a rock in the centre of a bend towards the left, and opposite to two more islands.  This valley has wide low grounds covered with high grass, and in many with a fine turf of green sward.  The soil of the highlands is thin and meagre, without any covering except a low sedge and a dry kind of grass which is almost as inconvenient as the prickly pear.  The seeds of it are armed with a long twisted hard beard at their upper extremity, while the lower part is a sharp firm point, beset at its base with little stiff bristles, with the points in a direction contrary to the subulate point to which they answer as a barb.  We see also another species of prickly pear.  It is of a globular form, composed of an assemblage of little conic leaves springing from a common root to which their small points are attached as a common centre, and the base of the cone forms the apex of the leaf which is garnished with a circular range of sharp thorns like the cochineal plant, and quite as stiff and even more keen than those of the common flat-leafed species.  Between the hills the river had been confined within one hundred and fifty or two hundred yards, but in the valley it widens to two hundred or two hundred and fifty yards, and sometimes is spread by its numerous islands to the distance of three quarters of a mile.  The banks are low, but the river never overflows them.  On entering the valley we again saw the snow-clad mountains before us, but the appearance of the hills as well as of the timber near us is much as heretofore.

Finding Chaboneau unable to proceed captain Clarke left him with one of the men, and accompanied by the other went up the river about twelve miles to the top of a mountain.  Here he had an extensive view of the river valley upwards and saw a large creek which flowed in on the right side.  He however discovered no fresh sign of the Indians, and therefore determined to examine the middle branch and join us by the time we reached the forks:  he descended the mountain by an Indian path which wound through a deep valley, and at length reached a fine cold spring.  The day had been very warm, the path unshaded by timber, and his thirst was excessive; he was therefore tempted to drink:  but although he took the precaution of previously wetting his head, feet and hands, he soon found himself very unwell; he continued his route, and after resting with Chaboneau at his camp, resumed his march across the north fork near a large island.  The first part was knee deep, but on the other side of the island the water came to their waists and was so rapid that Chaboneau was on the point of being swept away, and not being able to swim would have perished if captain Clarke had not rescued him.  While crossing the island they killed two brown bear and saw great quantities of beaver.  He then went on to a small river which falls into the north fork some miles above its junction with the two others:  here, finding himself grow more unwell, he halted for the night at the distance of four miles from his last encampment.