BIOLOGICAL, RECONNOISSANCE AT FLATHEAD LAKE. 155 



It seems very probable that the Swan river formerly flowed north 

 along the base of the Swan range on the west, emptying into Flathead 

 river north of Columbia Falls. The evidence for this is as follows. Be- 

 tween Rost lake and Swan river, a distance of but a little over a mile, 

 the surface is low, level, boggy, and swampy. The impression is that 

 the soil is the recently uncovered bottom of a quiet lake. Rost lake has 

 been described. North of this lake for several miles the surface alter- 

 nates with open and wet meadows, boggy woods, and swamps that par- 

 tially dry in summer. This condition seems to prevail north to the end 

 of the Swan range. Pasing from the mountains westward at Rost lake 

 the surface is as follows: First are the timbered slopes immediately west 

 of the range; next is the mud bottomed lake with its swampy border; 

 then come the open woods on higher and drier morainal sandy soil; fur- 

 ther west is the low end of the Mission range, rounded by ice; beyond is 

 the valley of the Flathead river. 



North of this line just drawn the swamp region takes the place of 

 Rost lake, widening so as to include Echo lake and territory east of 

 it. Further north the end of the Mission range disappears, blending with 

 the morainal drift, which lies continuous with the Mission and parallel 

 with the Swan range. The low and wet belt, narrowing to a small strip, 

 lies between the morainal ridges and the mountains. The only expla- 

 nation to be offered for this conspicuously low and swampy region is that 

 it is the remnant of the old stream. 



Adopting this view as a basis for argument it would appear that the 

 river formerly flowed north as previously indicated. In the Rost lake 

 region it probably widened into a lake with swampy bottom. 



I have no opinion as yet concerning the manner of closing the channel 

 so as to turn the river westward. The great bend made by the water 

 as it flows north from Swan lake, then west, south and again west seems 

 to indicate a dam by ice, possibly an unusual ice flow from the region of 

 MacDougal peak, where remnants of glaciers still remain. In event 

 of such an ice dam, which may have occurred farther north than the 

 point suggested, even to Flathead river, the waters from the west side of 

 the Swan and east side of the Mission ranges would be imprisoned, dam- 

 ming up far beyond the present head of Swan lake. The elevation ne- 

 cessary in order to overflow westward across the end of the Mission range 

 is not determined, but it is not great. The water began cutting through 

 the low gap. The cutting was rapid. The water meandered over the wide 

 level valley left comparatively dry, seeking escape, flnally making the 

 present tortouous channel. 



The lake is a place of great interest to a biologist. Having no sur- 

 face outlet its animal life presents many striking peculiarities. In its 

 waters was found a new hydra.Hydra corala Elrod and Ricker, elsewhere 

 described. In the same locality where the hydra was collected was 

 found a species of Polygonum which has been growing in shallow water 

 since the rise of the lake, before that being undoubtedly on dry meadow 

 banks. This plant has accommodated itself to its new surroundings, and 

 adapted its structure to the new conditions. The joints are swollen to 

 considerable proportions, conspicuously noticeable. The lake contains an 

 abundance of entomostracan life. 



