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 ig 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. Im 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, finally 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 
panks. 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. 
