18] 
In Dogfish Lake (Table VI.) the conditions are essentially 
those of Quiver Lake, of which it is an arm. The principal 
difference hes in the fact that flood water entering Quiver 
Lake at low stages never moves as far up as our station in Dog- 
fish Lake (PI. II.). Floods from Quiver Creek also merely back 
up the clear water in Dogfish Lake without themselves invad- 
ing that territory. The only flood silt entering this region is, 
consequently, that which comes with general inundations. 
In Flag Lake (Table VII.) the conditions at inundation are 
similar to those of other impounding backwaters. The great 
amount of vegetation found here adds to both the vegetable 
and the flocculent debris which roil the water whenever this is 
disturbed by waves or the movements of fish. Turbidity is 
but rarely caused by plankton here, with the exception of the 
few instances when diatoms or Oscillaria became very abun- 
dant. The water is thus usually clear, the bottom being 
commonly visible in the small spaces left free of vegetation, 
even at a depth of 215 cm. 
In Phelps Lake (Table [X.) the silt conditions are peculiar. 
The high level at which the lake lies and the intervening 
stretch of bottom-lands (PI. II.) combine to keep out all silt- 
laden flood-waters except those that enter by a now abandoned 
channel from Spoon River or from the main stream at times 
of their maximum floods. At other times the silt consists prin- 
cipally of particles of bark and dust from the adjacent forests, or 
of fragments of loam from the bottom, which is here unusually 
stable. The comparative freedom from vegetation removes a 
large element common in the silt of the other lakes. The turbid- 
ity, however, is very marked in this lake, falling in many cases 
below 20 cm., and in the majovity of instances is largely due to 
the very abundant plankton characteristic of its waters during 
the greater part of the summer. Movements of fish and water- 
fowl add considerably to the silt in suspension in this lake at 
some seasons of the year. 
The color of the water has not been made a subject of 
special inquiry. In general the turbidity gives it a grayish cast 
