OHIO STATE ACADEMY OK SCIENCE 



volume of water greatly exceeded that now discharged tlirough 

 the valley." 



We have seen why tlie volume of water sliould be greater tlian 

 at ]iresent; Init as yet lia\-c given no reason why the flow should 

 not be correspondingly vigorous. That it was greater, is evident 

 from tlie loess at Cape Girardeau; and as this is near the wide 

 flood ]dain on wliich the water could rusli out as into a sea, the 

 obstruction that would hold it back must be close at hand. 



Leverett says, again, "The Ohio at one time discharged either 

 wholly or in part through the '^Cache Yalley,' which crosses soiithern 

 Illinois a few miles north of the present course of the Ohio." 

 The "clay deposit stands only about seventy-five feet above the 

 present stream. [It] lias sufficient dei)th to extend to river level, 

 and it may extend much lower." The "Grand Chain of the Ohio," 

 crosses the river below the point of divergence of the old channel 

 from the one now occupied by the river. 



Clearly, we have here a condition similar to that at Thebes. 

 At the time under consideration the Ohio received all the glacial 

 discharge east of that flowing into the Illinois and Mississippi, in 

 addition to the floods from its southern tributaries swollen by 

 rainfall greater than we now know. These torrents flowed through 

 C^ache valley, over a bottom which is now seventy-five feet above 

 river level. The water thus discharged would equal or perhaps 

 exceed that coming from the north ; each great river would retard 

 the flow of the other, and in the comparatively sluggish currents 

 above their junction sediment would come to rest. This condition 

 prevailed until the ancient beds, excavated in geological ages ante- 

 dating the glacial period, were filled up. At Grand Tower and 

 at Thebes, the Mississippi when it was once more free to flow south- 

 ward without hindrance fonnd the clefts through which it now 

 flows, lower than the silt in its old channel. So the Ohio Cache 

 valley was filled to a level higher than the crevices in "Grand 

 Chain," and the water made its way through these. Probably the 

 Tennessee had discharged directly into the Mississippi; but this 

 region has not been fully studied. 



The sharp peaks, bluffs, and ridges of loess on the up]Der rivers 

 are the counterparts of the broad bottom lands along the lower 

 Ohio. In the one case, the land is high enough above sea-level to 

 permit aerial sculpturing; in the other, erosion can not act because 

 the gradient is almost at the base line. All, alijve, are due to sedi- 

 ments carried by glacial floods; the components being the various 

 earthy materials which ice and water have ground from rocks, 

 jDicked up from soils, mingled by ceaseless grinding and washing, 

 and finally carried in suspension until in quiet waters behind pro- 

 jecting hills, or in lake-like expanses of over-flowing back-water, 

 they settle to the bottom to form picturesque landscapes where 

 carved by winds and frost, or stretch out in plains of wonderful 

 fertilitv where these agencies do not erode them. 



