186 Transactions of the Academy of Science of St. Louis 
sistant to erosion than the alluvium, Hubbel Creek has been un- 
able to widen its trough near its mouth. 
Fragments of the Festus Terrace may be traced northward 
from St. Louis several miles. They are visible in the entire Mid- 
dle Mississippi River section. As previously pointed out, the 
gradient of the Festus ‘Terrace is about four inches per mile, 
while that of the Mississippi and Illinois rivers in this general 
vicinity is between six and seven inches per mile, and the grad- 
ient of the Missouri River is nearer twelve inches per mile. It 
will then be seen that the Festus Terrace approches the level of 
the flood plain of the Mississippi upstream, and unless there 
were some change in the slope of the terrace or the gradients 
of the rivers, it would be expected that the Festus Terrace would 
eventually merge upstream with the recent alluvium in the flood 
plain. This is precisely what happens up the Missouri River. 
This study did not carry the work up the Mississippi or lilinois 
rivers far enough to determine whether or not such a merging 
takes place. Rubey’ has recently traced a terrace along the 
Illinois River in Calhoun County, which may be correlated with 
the Festus Terrace. He called it the Deer Plain Terrace. 
THE CUIVRE TERRACE 
Between Winfield, Lincoln County, Missouri, and Grafton, 
Jersey County, Illinois, the Mississippi River flows in a great, 
semi-circular are, first south, then east, and then north, This 
arc is bordered on the west, south, and to a somewhat less €X- 
tent on the southeast, by two very extensive, flat surfaces. Both 
can be seen at St. Peters, St. Charles County, Missouri (Fig. 7). 
The lower one has an elevation of 450 feet. It is a part of the 
Festus Terrace. The upper terrace has an elevation of about 510 
feet. It is to this upper surface that attention is now directed. The 
surface is somewhat dissected by youthful streams; but the view 
from the top of the terrace shows the broad expanse of flat 
surface, which is also shown on the topographic map. The ter- 
race in this vicinity extends along the Mississippi River in 4 
