238 GEOGRAPHICAL MEMOIR. 
nearly direct course eastward for eighty miles, discharging into the Missouri three miles 
above the Falls. About fifty-five miles from its mouth it receives Elk Fork from the mountains 
a little south of west, up which a good approach can be made to Lewis and Clark’s or Cadotte’s 
Pass. Crown Butte creek із а stream not more than fifteen miles long, which rises near the 
hill of that name, and running eastwardly empties into a lake, together with a smaller stream 
from the south. Its outlet runs only a short distance and then sinks into the ground five miles 
from the Missouri, between Sunriver and Beaver creek. The Dearborn, rising in the main chain, 
about ten miles southeast of Elk Fork, runs first northwestwardly for ten miles, and then turning 
to the southeast flows nearly parallel to the dividing ridge for twenty miles, receiving a 
tributary from both Lewis and Clark's and Cadotte's Passes, when it gradually curves round 
to the east, and twenty miles further empties into the Missouri near latitude 47° 09, Two 
miles from its mouth it receives from the northwest Beaver creek, a stream not more than 
forty-five miles long, and running also nearly parallel to the dividing ridge. These two streams, 
together with the broken character of the country adjoining their lower portions, make an 
approach from the Missouri difficult above Sun river. 
Twenty-eight miles southeast of Cadotte's Pass rises Little Prickly Pear ereek, and, taking a 
crooked course towards the northeast for about twenty-five miles, empties into the Missouri 
thirteen miles above the Dearborn. Its valley forms a part of the approach from Fort Benton 
to the Hell-Gate passes. The principal Prickly Pear creek, however, rises by several heads 
from the Blackfoot passes and vicinity, and, running more towards the east for about twenty-five 
miles, empties into the Missouri above the Gate of the Mountains, and eighteen miles south- 
east of the preceding stream. It forms part of the approach to these passes from the head 
of the Muscle Shell by the route explored by Lieutenant Mullan in September, 1853. 
. No large stream runs into the Missouri above this stream until the three great forks, called 
by Lewis and Clark Jefferson, Madison, and Gallatin, are reached, about sixty-eight miles to 
the southeast. These three rivers, of nearly equal size, form the sources of the Missouri flowing 
from the lofty mountains which almost encircle its head waters towards the west, south, and 
east. Only the Jefferson Fork has, however, been traced to its sources, which were found by 
Lieutenant Mullan in the vicinity of Big Hole prairie and pass, where there is an excellent 
communication with the Bitter Root valley at its head near longitude 113? 50', and another pass 
to Deer Lodge prairie, sixty-five miles further east. Captain Clark followed it down in a canoe 
through its very winding course for about eighty-five miles in a direct line to where it joins 
Madison Fork. The Muscle Shell is the principal river which enters the Missouri on the south 
side, joining it near longitude 1089, 1% rises in the Girdle mountains in latitude 46° 30’, longi- 
tude about 110°, and running eastward for about one hundred and sixty-five miles, turns a spur 
of the Judith range and takes a general northeast course for ninety miles to its mouth. When 
crossed by Lieutenant Mullan, at least one hundred miles above its mouth, it was forty or fifty 
yards in width and from two to four feet deep, with a very rapid current. This was in the dry 
season in September. Judith river is the next, emptying about eighty-four miles west of the Mus- 
cle Shell, and rising by numerous branches in the Girdle and Judith ranges between which it runs, 
having a course generally north for about sixty miles. From the frequency of its branching, it 
does not seem likely to be useful for the purposes of navigation. Arrow river, which empties 
nine miles west of it, also rises by three branches in the Highwood range, a spur of the Girdle 
mountains. Its sources are not more than thirty-five miles from the Missouri, and it can only 
be serviceable for rafting. The next streams on this side are above Fort Benton. Shonkin 
