ROCK ISLANDS IN OHIO VALLEY. 85 



mile. Like Monument Hill, it is separated from the uplands east of the 

 river by a narrow channel, less than half a mile in average width, with a 

 gravel filling that extends down about to river level. The cause for the 

 excavation of a double channel at this place is not yet apparent. 



Opposite the mouth of Middle Island Creek, which enters the Ohio at 

 St. Marys, W. Va., a rock island is found on the Ohio side which stands 

 about 300 feet above the river. It is separated from high land on the 

 north by a channel about one-third of a mile in width, whose surface is 

 only 50 to 60 feet above the river, and is still utilized at extreme high 

 water. It is probable that this island has been cut off from the uplands on 

 the north by the encroachments of the Ohio River. The stream is now 

 encroaching upon the east side of the island, and it appears formerly to 

 have made an ox-bow curve, which encroached on its west side. 



At the mouth of the Little Kanawha River, at Parkersburg, W. Va., 

 there is a rock island which stands about 180 feet above the river. It is 

 separated from the east bluff by a gravel-filled valley about one-half mile 

 wide, whose surface is 75 to 80 feet above the river. The width of this 

 channel is only one-third as great as that occupied by the Ohio west of the 

 island, but about the same as the valley of the Little Kanawha south of the 

 island, and it may have been excavated by the latter stream. Well data 

 suggest, though they are not full enough to demonstrate, that the abandoned 

 channel has a lower rock floor than the present channel of Little Kanawha. 

 This being the case, the island has probably been cut ofi" from the vipland 

 south of the Little Kanawha River. Encroachments, either by the Little 

 Kanawha or by the Ohio, may have opened a passage for the present 

 course of the stream. 



An island or irregular group of hills in the north part of Cincinnati, 

 known as Walnut Hills, stands 300 to 400 feet above the river and sepa- 

 rates a broad abandoned channel on the north from the narrower present 

 valley of the Ohio on the south (see PI. V). At the west it is bounded by 

 Mill Creek Valley. The Walnut Hills island apparently once had connec- 

 tion with the uplands south of the Ohio, between the Licking and Ohio 

 rivers, but tlu-ougli a diversion of the Ohio has been separated from thos6 

 uplands. In this connection it may be remarked that the old Ohio appears 

 to have taken a northward course from Walnut Hills to the Great Miami 

 near Hamilton, Ohio, and to have received the Licking through the lower 



