BIOLOGICAL RECONNOISSANCE AT FLATHEAD LAKE. 123 
The Mission Valley. 
This beautiful valley is bordered by the Mission mountains on the 
east, the Jocko river on the south, the Pend d’Oreille river on the west, 
Flathead lake on the north. The extreme length is about 35 miles, the 
extreme width about 15 miles. A terminal moraine separates the lake 
from the valley, bordering the lake on the southern end. The country 
immediately south of the moraine for a distance of ten miles is beautiful. 
It is level land, rich, capable of making good farms, easily irrigated. A 
large sand dune stretches across the valley about 15 miles from the lake, 
extending east and west. The eastern end is free sand, is not yet held 
in place by vegetation, and is slowly creeping eastward. The free and 
movable sand is 12 to 15 feet high, clean looking and white. Some eight 
or ten miles from this free sand westward one comes to the Pend d’Oreille 
river. The country abounds with depressions and coulees, with several 
large buttes trom 100 to 200 feet high. It is in this region that the 
buffalo herd ranges. 
The valley is crossed by four large creeks, as follows: Mission creek 
is the most southern. It takes its source in two canons, one the outlet of 
Sinyaleamin lake, the other Mission creek proper, with its high 
falls, visible for miles on the plain. Sinyaleamin lake receives 
its water from the eastern slopes of the mountains, principally from Snow 
lake, which is full of slush snow even in July. The stream leaving Snow 
lake tumbles over a beautiful cascade just before it enters the lake. The 
lake is described elsewhere. The stream from this lake joins Mission 
creek proper a short distance from St. Ignatius Mission. A third and 
smaller branch emerges from the canon between Mission canon and Mc- 
Donald lake. This branch takes its rise in two small and beautiful alpine 
lakes, Twin lakes, lying high up in the mountains, fed by melting snows. 
Except in early spring this water is consumed in irrigation. Mission creek 
flows a little to the north of west, receiving Post creek a few miles west 
of the Mission, finally flowing into the Pend d’Oreille river, Mission 
creek may be located by examination of Plate XIX. Post creek is the 
outlet of McDonald lake, which receives most of its waters from the 
slopes of McDonald peak. The creek forming the inlet of the lake has 
two forks, one taking the waters from McDonald peak, the other from the 
peaks immediately to the north. This northern branch flows through 
two small lakes, and has some beautiful cascades, seen plainly from Mc- 
Donald peak. Neither of these branches is known save for a very short 
distance from the lake. Post creek flows southwest into Mission creek 
as previously mentioned. Crow creek takes its rise in the mountains 
still farther to the north, in the canon through which runs the Crow creek 
trail. This trail is the Indian route across the range to the Swan river 
and Big Blackfoot river country. As it crosses the range at a high altitude 
it is passable only in summer, and is the only passageway between the 
Jocko river and the northern end of the Mission range. The creek flows 
a little south of west, receiving Mud creek near the sand dune previously 
mentioned, and flowing into the Pend d’Oreille river. It is a large creek, 
