464 
ton-rich channel water, or its partial replacement by the plank- 
ton-poor and silt-laden flood. Typical illustrations of its action 
appear in the planktograph of 1896. 
The rising stages of the flood are the most disastrous. They 
carry the heaviest burden of silt, are formed of the most recent 
water, and usually, because of their sudden inroads, most com- 
pletely replace the previous channel contents. The December 
flood of 1895 is a typical illustration. Rising suddenly from 
low levels (3 ft.) to overflow stage (12.6 ft.) in 12 days, it de- 
pletes the channel plankton from 2.6 cm‘ in the initial stages 
of the flood on the 20th (PI. IX.) to .08 on the 25th, if not, in- 
deed, earlier. Not only does it thus depress plankton content 
in channel waters but, with a less catastrophic completeness, 
that also in the backwaters. Thus in Thompson’s Lake the 
plankton falls from 1.87 cm.’ on the 19th to .13 on the 28th, 
in Quiver and Dogfish lakes, from .63 and 10.57 to .29 and 
.06, and in Flag Lake, from 6.38 to 3.26. The effectiveness of 
the depletion is greatest where overflow currents are best es- 
tablished, as in Thompson’s and Dogfish lakes, and least where 
the currents are slight and impounding greatest, as in Flag 
Lake. 
With the culmination of the flood the proportions of in- 
coming storm water of recent origin decline rapidly, the effects 
of the run-off of impounded backwaters begin to appear, and 
recovery in production, other things being equal, marks this 
stage of the flood. Typical illustrations will be found in the 
June and August floods of 1896 (Pl. X.) and in the June flood 
of 1897 (Pl. XJ.) and 1898 (Pl. XIT.). 
The results of flood in the backwaters are similar to those 
in the channel wherever currents of overflow are established 
and replacement of the plankton-rich contents of the lake by 
flood waters ensues, as has just been shown. Usually there are 
accessory bottom-lands, not swept by current, where a part of 
‘the original lake waters are retained, and where plankton 
breeds abundantly. As a result of this, the recovery from the 
depletion by flood—and this is usually not so complete as in 
