ROCK RIVER DRAINAGE BASIN. 489 



Along the south tributary of Leaf River the limits of preglacial exca- 

 vation are clearly marked as on Bluff Creek. The excavation on Rocl? 

 River increases from 25 feet or less to about 75 feet. The width of this 

 portion of the valley is about 2,000 feet. The excavation is estimated to 

 be 60 mile-feet. 



On the divide between the preglacial Leaf and Kite rivers the excava- 

 tion appears to have ranged from 60 feet up to perhaps 125 feet in depth, 

 and the width is somewhat uniformly about 2,000 feet (see fig. 6, No. 6). 

 The excavation is estimated to be 75 mile-feet. 



In the Kite River Valley and associated lowlands the excavation appar- 

 ently ranged from zero to about 50 feet in depth. In Kite River Valley 

 the width is a mile or more, but below the valley it is about 2,000 feet. An 

 average cross section is shown in fig. 6, No. 7, which is at Oregon. The 

 excavation is estimated to be 125 mile-feet. 



South of Kite River the depth of excavation appears to scarcely 

 exceed 50 feet, and no sharply defined col could be found, for, being in 

 the St. Peter sandstone area, the uplands are very uneven. The width of 

 excavation is 2,000 to 2,500 feet, and the total excavation is estimated to be 

 only 40 mile-feet. The profile shown in fig. 6, No. 8, is found at D, 

 PL XII, and may perhaps cross at the site of an old col. 



The depth of excavation along the portion of Rock River between the 

 place shown in this profile and the Green River Basin has not been so 

 carefully computed as in the portions above. The river appears to follow 

 the line of a small preglacial stream as far as the mouth of Pine Creek, 

 whose valley has been somewhat broadened by it. Below the mouth of 

 Pine Creek the preglacial valley has been widened but little. The average 

 width of the valley is about one-fourth mile, and in places it reaches nearly 

 a mile. Such is the case at the sharp bend at Grand cle Tour and at bends 

 near Dixon. The rock excavation may possibly amount to 500 mile-feet 

 in this lower 20 miles, but it seems as probable that it does not exceed 400 

 mile-feet, and it may be even less. 



Combining the above estimates, it appears that there has been not 

 more than 1,055 mile-feet of excavation in the 49 miles of this narrow 

 section of the Rock River Valley, and possibly it falls below 1,000 mile-feet. 

 It may, therefore, be roughly placed at one-fifth of a cubic mile. The 

 present discharge through this valley, based upon estimates by Greenleaf 

 and by Rae, is somewhat more than 4,000 cubic feet per second, that being 



