GEOLOGY OF LA SALLE COUNTY. 



157 



rivers in the extreme southeast part of Ausable Town- 

 ship, Grund\^ count}^ (Section 23, Township 34 north, 

 Range 8 east), pursues a general westerly course for 

 about fift3^-seven miles in an air line, about sixty-six 

 miles by the course of the stream, and then strikes to 

 the south-southwest. Of its affluents in La Salle 

 county, water powers have been developed on the Big 

 Vermillion, Fox and Pequamsauggin, on the Illinois 

 itself, and on Indian creek, a branch of the Fox. 



The Illinois sends down, when at its greatest 

 heighth, about 65,000 cubic feet of water per second, 

 but at its lowest stages as little as 1,070 cubic feet per 

 second, or one sixt}— fifth of its greatest flood volume. 

 When the country was new the floods were less exces- 

 sive and the stream did not fall so low as now. The 

 whole drift of man's improvements has been to cause 

 the river to rise more rapidly, fall more quickly, and to 

 reach a lower stage in times of drought than it did 

 prior to the settlement of this region; but even 1,070 

 cubic feet of water per second- is not to be 

 despised, as it equals 64,200 cubic feet per minute, 

 and this with twelve feet fall equals about 

 1,460 horse-power; but at Ottawa 14^ feet fall can 

 be used east of the city, and 8or 10 feet west 

 of it, giving at its lowest stages 1,700 horse power 

 on one side and 980 horse power on the other, while 

 at medium stages with a discharge of 2,500 cubic feet 

 of water per second we have for each site 2>^ times 

 the above, or 4,200 horse power on the east and 

 2,400 horse power on the west, a total of 6,600 

 horse power, or one of the finest powers in the 

 country. We have introduced no hypothetical figures 

 here as to what may be some time, somehow, some- 

 where, but have taken the facts as they are now^ 



But the total power that ma}^ be developed from 



