d 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.

Saturday 27. We proceeded on but slowly, the current being still so
rapid as to require the utmost exertions of us all to advance, and the
men are losing their strength fast in consequence of their constant
efforts. At half a mile we passed an island, and a mile and a quarter
further again entered a ridge of hills which now approach the river with
cliffs apparently sinking like those of yesterday. They are composed of
a solid limestone of a light lead colour when exposed to the air, though
when freshly broken it is of a deep blue, and of an excellent quality
and very fine grain. On these cliffs were numbers of the bighorn. At two
and a half miles we reached the centre of a bend towards the south
passing a small island, and at one mile and a quarter beyond this
reached about nine in the morning the mouth of a river seventy yards
wide, which falls in from the southeast. Here the country suddenly opens
into extensive and beautiful meadows and plains, surrounded on every
side with distant and lofty mountains. Captain Lewis went up this stream
for about half a mile, and from the height of a limestone cliff could
observe its course about seven miles, and the three forks of the
Missouri, of which this river is one. Its extreme point bore S. 65
degrees E. and during the seven mile