Mississippi Drainage System. — Westgate. 247 
new and level plain sloping gradually away to the northwest. This 
slope was probably greater than the slope of the beds as thej- were 
deposited, for the beds doubtless shared more or less in the eleva- 
tion which had taken place on their southeast margin. The drain- 
age of this elevated mountain region would extend itself across 
this plain to the northwest, the direction of flow being deter- 
mined by the slope of the surface. The crystallines of Canada 
and the Paleozoic sediments which had been forming in the sea 
south of them appear to have been elevated at about the same 
period, so that the whole of the eastern Mississippi basin became 
dry land. Whether the Canadian uplift was of continental extent 
and the present dip of the stratified rocks is merely the slope of 
the old Paleozoic sea bottom, or whether there was a differential 
uplift b}' which the northern portions were more elevated than the 
southern, is not known. In either case there would be a south- 
ward slope from the crystallines over the newly emerged plain. 
The southward drainage from the Canadian highlands and the 
northwestward drainage from the Appalachian region would unite 
and form a trunk stream flowing westward and occupying the posi- 
tion of the present Ohio. The Archean area of Wisconsin, which 
existed as an island in the old Paleozoic sea, formed a more or 
lesselevated nucleus after emergence, with Paleozoic strata sloping 
away from it in all directions; and the drainage of Wisconsin 
would consist of streams flowing out radiall}^ from its Archean 
core. The outlet of all these streams, — of the trunk stream drain- 
ing the Canadian and Appallachian regions, of the westward flow- 
ing streams from the Archean area of Wisconsin and from the 
Archean area to the north in Minnesota and British America, — 
would be to the west, discharging into a Mesozoic sea, the limits 
of which have not been determined. 
It is now necessary to compare this hypothetical post-Carbonif- 
erous drainage of the eastern Mississippi basin with the present 
drainage. If the two are found to agree in whole or in part, that 
part of the present drainage which corresponds with the hypothet- 
ical post-Carboniferous drainage may be considered to have been 
determined in its general direction at the time of the Appalachian 
uplift. Where lack of correspondence between the two exists, the 
differences will be examined in detail. 
Comparing the present with the supposed post-Carl)oniferous 
system, the rivers south of the Ohio are seen to flow northwest in 
