BIOLOGICAL RECONNOISSANCE AT FLATHEAD LAKE. 135. 
Flathead Lake. 
The following report of the lake was prepared by Fred. D. Smith, 
formerly Professor of Chemistry and Geology at the University of Mon- 
tana, now mining engineer at Sumpter, Oregon. The paper was prepared 
while he was connected with the University, after he had made an ex- 
tended trip around the lake and over a large portion of the country ad- 
jacent. 
“The lake occupies the lower portions of an immense valley that 
reaches from a low range of hills along the Jocko river northward across 
the British Columbia line, and which has a total length of over 100 miles. 
Tobacco Plains on the north are a part of this valley though separated 
from Mission valley by a low range of hills. This larger valley may be con- 
sidered made up of three smaller ones, viz: Mission, south of Flathead 
Lake; Flathead, north of the lake, and Tobacco Plains still farther north. 
Mission valley has a general elevation of from 100 to 250 feet above the 
lake level and a length of about 35 miles north and south with a width of 
from 5 to 10 miles. Flathead valley has a slight elevation of from 20 to 
50 feet above the lake and is much more regular in its surface contour 
and its width. Its length is about 40 miles and the width 8 to 10 miles. 
These two valleys are the more important in this discussion as each illus- 
trates a geological process bearing on the history of the lake. (The lower 
portion of Flathead valley may ve studied from Plate XXXVII.) 
The present lake is the remnant of the much larger lake that occu- 
pied these valleys in Tertiary times, as shown by the lake beds in both 
valleys as well as in the valley through which the Jocko river flows. As 
yet little, if any, investigating for vertebrate fossils has been done in 
these beds though it is probable that they are of the same age as those 
of Flint creek and Madison valley studied by E. Douglass. 
Mission valley and the lake are bordered on the eastern side by the 
Mission mountains, a range which rises abruptly from the plains to great 
heights. These mountains, with a very steep western slope, have their 
summit within relatively short distances from the valley and consequently 
the streams therefrom are neither large nor of great volume in discharge. 
On the other hand the eastern slopes of the mountains are long and grad- 
ual, thus furnishing a larger drainage area to the Swan river and Black- 
foot tributaries which receive the waters. This range, as such, appears to 
terminate at a point near the upper end of the lake where the Swan river, 
changing its course from northward to west and south westward, flows 
into Flathead lake. Another range, the Swan range of the Kootenais, 
some 12 miles to the N. E. continues to be the border of Flathead valley 
in a manner similar to that of Mission range just explained. 
The history of these valleys or of the one larger valley, when all are. 
considered as one, is very interesting. The Mission mountain range was 
caused by a fault, having a general direction of north and south, with a 
