1887] Geology and Palaontology. 169 
‘0.35 foot per mile, while that of the ancient bed is indefinitely 
greater, as shown from the record of the borings of the deep 
well at New Orleans. From New Madrid to St. Louis the slope 
of the valley is 0.73 foot per mile, but above it is reduced to 
about half a foot, throughout a long stretch below Rock Island 
Rapids. Above the Rapids (where the fall is twenty-two feet in 
fourteen miles), for two hundred miles the slope, so much nearer 
its higher waters, is again reduced to only 0.28 foot per mile. 
The valley at St. Louis is about eight miles wide. Within a 
mile of its western side, as shown at the eastern abutment of the 
St. Louis bridge, the old channel reaches to a depth below the 
flood-plain of one hundred and thirty-six feet, increasing towards 
the eastward. Therefore there is every reason to conclude that 
from New Madrid to St. Louis, or even above it, the floor of the 
of that above and below this region, but without success. 
North of St. Louis the floor of the buried valley rises. 
It is not known whether the modern channel of the Des Moines 
Rapids at Keokuk has been produced by erosion into the rocky 
floor, exposed by the upward warping of the earth’s crust, or 
by the river deflected over hard rock by the filling up of War- 
ren’s channel to the westward. 
| been stated, the slope of the valley above Rock Island 
Rapids is only half that below. But a more striking difference 
