up of pebbles, and in the bank, at the level of the water, is a
conglomerate of coarse pebbles, about the size of ostrich eggs, and which
I remarked in the banks of the Laramie fork. It is overlaid by a soil of
mixed clay and sand, six feet thick. By astronomical observations, our
position is in longitude 106 deg. 54' 32", and latitude 42 deg. 38'.

30th.--After traveling about twelve miles this morning, we reached a place
where the Indian village had crossed the river. Here were the poles of
discarded lodges and skeletons of horses lying about. Mr. Carson, who had
never been higher up than this point on the river, which has the character
of being exceedingly rugged, and walled in by precipices above, thought it
advisable to encamp near this place, where we were certain of obtaining
grass, and to-morrow make our crossing among the rugged hills to the Sweet
Water river. Accordingly we turned back and descended the river to an
island near by, which was about twenty acres in size, covered with a
luxuriant growth of grass. The formation here I found highly interesting.
Immediately at this island the river is again shut up in the rugged hills,
which come down to it from the main ridge in a succession of spurs three
or four hundred feet high, and alternated with green level
_prairillons_ or meadows, bordered on the river banks with thickets
of willow, and having many plants to interest the traveler. The island
lies between two of these ridges, three or four hundred yards apart, of
which that on the right bank is composed entirely of red argillaceous
sandstone, with thin layers of fibrous gypsum. On the left bank, the ridge
is composed entirely of silicious pudding-stone, the pebbles in the
numerous strata increasing in size from the top to the bottom, where they
are as large as a man's head. So far as I was able to determine, these
strata incline to the northeast, with a dip of about 15 deg.. This pudding-
stone, or conglomerate formation, I was enabled to trace through an
extended range of country, from a few miles east of the meridian of Fort