BIOLOGICAL, RECONNOISSANCB 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 oe 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 th& 

 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 Kootenals, 

 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 



