350 The American Geologist. .Tunc, isoi 
likely another of these early rivers. Of course only the stronger 
streams could maintain their courses across the obstruction caused 
by the rising folds. As a rule an entirely new river system was 
developed in the more strongly folded areas of the Alleghanies. 
Even the Ohio river itself from the mouth of Teaze's valley to a 
point near the southwestern corner of Pennsylvania, and the lower 
course of the Alleghany seem to be of later age than the period 
of folding and occupy approximately the middle of the great syn- 
clinal valley between the Cincinnati anticlinal and the Alleghanies. 
The northwestern tributaries of this newer portion of the Ohio 
often have a strikingly similar direction to those which enter the 
Ohio from the other side. AVhen such streams from opposite 
sides enter the Ohio at about the same point, they are suggestive 
of the existence of a former continuous stream which had been cut 
in two by the process of folding and the formation of the syn- 
clinal portion of the Ohio. The northwest stream in this case 
may then be considered to have had its flow inverted as far as the 
Ohio. However the mere fact that the streams are flowing to- 
wards the centre of a synclinal trough might also be considered a 
sufficient explanation for their existence. 
If land conditions over the area here discussed, previous to the 
period of folding be admitted, then the intersection of the Cincin- 
nati-Nashville anticlinal by the rivers mentioned is not so surpris- 
ing. Then also the cutting of the channel of the Tennessee across 
the Cumberland plateau near Chattanooga is made possible. 
That such land conditions existed is made probable b}' the dis- 
appearance of all marine fossils soon after the opening of the Coal 
Measure period, and the finding of stumps of trees in many of 
the deposits of this period in situ, at widely scattered points of 
this area. 
The Tennessee river at present has a channel 1400-1500 feet 
below the more elevated portions of the Cumberland plateau where 
it cuts through this tableland. At the time it was maintaining 
its course across the growing obstruction of the Cincinnati-Nash- 
ville anticlinal, it very likely had a relatively much higher alti- 
tude ; indeed its course at that time ma}* have been a thousand 
feet, or even more above its present bed. If during this period, 
while the channel of the Tennessee was a much less striking 
feature in this synclinal region, the level of the sea was not 
much below the general level of the present Cumberland plateau, 
