447 
The comparison of backwater and channel production in 
1898 is in some contrast with that in 1897. In 1897, omitting 
Spoon River, production in backwaters exceeded that in the 
channel in 29 of 40 monthly averages, or in 73 per cent., while 
in 1898 the excess occurs only in 26 of 37, or in 67 per cent. 
The excess, moreover, is frequently of less amplitude in the lat- 
ter year, as is seen in the relation of the means of the monthly 
averages of backwaters and channel in the two years. Thus in 
1897 production in Thompson’s Lake (10.41) was 217 per cent. 
in excess of that in the channel (3.28), while in 1898 (5.06 and 
2.03) the excess was only 149 per cent. In Phelps Lake, on the 
other hand, production rose to the unparalleled height of 37.34, 
the mean of the monthly averages, 67 per cent. above the mean 
of all monthly averages, and fourfold that in the previous year, 
when the last 4 months were cut off by the drying up of the lake. 
Production in Quiver Lake in this year is 1.96 cm.’, mean 
of monthly averages, or 2.44, average of all collections—12 per 
cent. and 44 per cent. above the mean respectively of all years. 
This larger production is due to the excessive production in the 
vernal pulses in May and June and to the high levels of pro- 
duction in November and December, rising 138, 78,217, and 176 
per cent. above the average respectively for these months. The 
hydrographic conditions in these months in Quiver Lake are 
favorable to increased production. The May and June pulses 
are at levels (11 ft.) when impounded run-off from slightly 
submerged bottom-lands to the north was rapidly draining to 
the channel through the lake. In November and December 
there was at least double the usual volume of water in the lake, 
due to a 34 per cent. increase in river levels, with a considera- 
ble reduction in the proportion of tributary water and increase 
in the impounding function. In the remaining 8 months of 
the year, then, average production is 79 per cent. below the 
general average for those months in Quiver Lake. This very 
considerable depression in production falls in the main in the 
period of greatest hydrographic disturbance. This body of 
water, owing to its frequent invasion by channel waters and to 
