THE OHIO VALLEY IN SOUTHERN INDIANA 265 



middle Lake Plain and northern Pigeon Plain south of the ter- 

 race ranges from 17 to 40 feet. Very few wells are deeper, and 

 only those near the bordering hills reach rock. One well, 56- 

 feet deep in the narrowest part of Lake Plain, did not reach 

 rock. In River Plain wells range from 30 to 60 feet in depth. 



From these wells can be learned something of the original 

 depth of this filled valley. If all sands, clays, and gravels 

 which underlie Lake, River, and a portion of Pigeon plains could 

 be. removed, a valley extending at least 56 and probably more 

 than 70 feet below the present plain level, and having its sides 

 of middle carboniferous strata, would be shown. 



The old cut-off. — This valley under Lake Plain and the south- 

 ern part of Pigeon Plain is the same depth as the half filled Ohio 

 gorge of which it is a continuation. It is filled with the same 

 materials. The hills on each side are capped with typical river- 

 bluff loess in the same manner as those on the erosion scarp of 

 the Ohio. The levels of the plain are so nearly the same that 

 a portion of the waters in the flood of 1884 flowed swiftly through 

 Lake Plain and entered Pigeon Plain, where one part followed 

 the terrace and then turned southward and met the other part,, 

 which flowed south of Lake P. O., joining the waters of the Ohio 

 again where Pigeon and River plains meet. This stream was four 

 feet deep at the junction of Pigeon and Lake plains. 



All these facts can lead to but one conclusion : The Ohio 

 River at one time flowed through the Lake Plain and down 

 through Pigeon Plain, entering the Ohio valley again betweeni 

 Enterprise and the eastern border of Warrick county. 



To the erosive power of the river is to be attributed the 

 greater part, if not the whole, of the gorge now occupied by 

 that portion of the plain which has been called Lake Plain. In 

 Pigeon Plain the work done was simply deepening and broaden- 

 ing on the eastern side of a broad valley extending from the 

 northeast, which the river entered after cutting through the rock 

 in Lake Plain. A portion of this more ancient valley, extend- 

 ing from the northeast, still remains intact north of the terrace,, 

 the terrace being simply the northern boundary of the Ohio's. 



