480 G. K. Warren— Valley of the Minnesota and Mississippi. 
been required there to have carried the river back again to its 
ancient channel during some extraordinary flood, and yet it 
might have been that the new channel would even after this 
remain the permanent one for ordinary stages. 
Such an explanation as this may be applicable to the cases 
at Fountain Bluff and at the Grand Chain on the Mississippi 
just above the mouth of the Ohio, and to the almost incompre- 
hensible changes of course in the Lower Ohio itself, shown on 
the general map. 
nother interesting supposition may be made that the Missis- 
sippi in the last terrace period might have succeeded in washing 
down the bluffs, separating it near Burlington from the Crooked 
Creek flowing into the Illinois. (See Diagram 1, sheet 4.) The 
new channel would have double the descent to the mouth of 
the Illinois of the existing one, and we might have gained a new 
course for the river, leaving a larger ancient channel occupied 
by a smaller stream, and there would have been set at work a 
new cause to modify all the valley of the Illinois River and all 
the Mississippi above. 
Summary of principal points presented.—I will summarize the 
principal facts that seem to be made out along the course of the 
Minnesota and Mississippi : 
. That the Minnesota Valley and the Mississippi Valley 
above the Ohio have been, asa rule, formed since the deposition 
of the glacial drift, for this exists in unmodified and modified 
forms in the banks of the river; and that the Winnipeg basin 
drained out southward along it. 
. . 
Rivers, and in the first instance considered what the results 
southern elevation and northern depression now going on. — I 
explains, by one widely exerted influence, many effects which; 
on the grounds of glacial action alone, requires many specl@ 
g- : 
I think this change of relative carson south and depression — 
north has been probably reversed at some periods, and repeated. 
This is important, for, if we can show that any movement 0 
