NARBATIVE OF 1853. 171 
The geological formation of the country between the headwaters of the Bitter Root river 
and the range of mountains separating the tributaries of the Missouri river and its forks from 
the Snake river belongs to the tertiary period, while that along the Jefferson Fork and its 
principal tributaries is limestone and conglomerate rock. From the Snake River divide the 
whole character of the country is changed, the geological formation being principally basaltic 
and volcanic. None of the streams flowing from the mountains along the route which Lieu- 
tenant Mullan travelled emptied into Snake river, but either sank into the ground or formed 
small lakes in the broad valley of Snake river; while, for sixty miles above Fort Hall, along 
the main stream of Snake river, there is but one tributary which flows in from the south, and 
none from the north. The soil generally is fertile and productive, and well adapted to grazing, 
except for that portion from the Snake River divide to Fort Hall, whose whole characteristic 
might be described in one word—sterility. 
On December 19 Lieutenant Mullan started on his return from Fort Hall northward, over 
the same route, for twenty miles north of where he had struck Snake river, then more to the 
east, up High Bank creek, which he followed to the base of the mountains, finding no snow 
until then, when (December 23) it was three inches deep. The streams were all frozen hard, 
and there was rio game; grass and wood were also very scarce. ` 
On the 24th he encountered a snow storm, the snow falling to the depth of six inches. The 
thermometer at sunrise was at 3° and only 22? at noon. High up the cañon of this creek there 
was some cedar, spruce, and aspen, but no timber on the mountains. "This cation was travelled 
by wagons from Fort Hall to the Bitter Root for the first time, іп 1840, оу Father De Smet. 
At nine miles from this stream he struck upon the waters of Hooked Man's creek, a branch 
of Jefferson Fork, crossing a low ridge with a very gradual slope. There was snow on the 
summit a foot deep, and in the morning the thermometer was as low as 14? below zero, and 
ice twenty inches thick on the streams. But, reaching the valley of Jefferson Fork, the snow 
was only six inches deep, and the animals obtained good grass under it. As he approached 
Jefferson Fork the snow and ice disappeared, and the weather became so mild as to make fires 
scarcely necessary. Another beautiful prairie appeared here, twenty-five miles east of Big 
Hole prairie, before deseribed, and, like it, surrounded by mountains. It was fifteen miles 
wide, and through it ran the Jefferson Fork, bordered with cottonwood, while the prairie, 
covered with grass, looked like a great field of yellow grain. Game was here exceedingly 
abundant, large bands of deer and antelope being seen; and this is the favorite hunting ground 
of the Indians, the mountains in the vicinity being filled with large numbers of bears, moose, 
and elk. The Jefferson Fork was here fifty yards wide and two feet deep at the fork. 
Lieutenant Mullan found a beautiful country towards the head of the Missouri, not far from 
the three forks— beautiful and well-grassed valleys that extended far towards the east in the 
direction of the Yellowstone, and which his guide told him retained the same general character 
to near the Black hills of Nebraska. 
Well-wooded streams, fertile bottoms, mild climate, even late in December, and uncounted 
herds of game grazing at every point, all tended to form a picture for which he was not pre- 
pared, and that showed the capability of the country in the most marked manner. e 
Near the Jefferson Fork the wooded mountains now gave place to low ranges of rolling 
prairie hills that lost themselves in the swelling prairies that constitute the great plains of the 
Missouri and Yellowstone, upon which graze the countless herds of buffalo, and, as he truly 
