Devonian Era in the Ohio Basin. — Claypole. 89 
Since writing the above, two papers have appeared bear- 
ing on this topic : G. C. Broadhead, American Geologist, 
Dec, 1894. A. W. Winslow, American Geologist, July, 1895. 
These contributions extend the range of the great southern 
uplift, on which so much stress has been laid, westward over 
the Missouri-Arkansas area, inasmuch as they indicate that the 
whole region was simultaneously affected by a movement in 
the same direction reaching from Georgia to and beyond the 
Ozarks. The existence of a southern channel of communica- 
tion in that direction must therefore depend on either an inter- 
ruption of the uplift at that point, where it cannot now be 
traced, or on a previous level so low that the elevation failed 
to bring it above water. In the latter case, we may regard it 
as an exceedingly ancient forecast of the Mississippi which 
would then have been at least indicated in Palaeozoic time. 
On the whole, the evidence afforded by these writers, both 
well acquainted with the ground, is not favourable to the exist- 
ence of a southern connecting channel at the date required by 
the theory of professor Williams. 
Change of Sediment. — Nothing is more striking in the Ap- 
palachian history of the Devonian era than the marked change 
of deposits which occurred during its passage. Opening with 
a continuation of the great limestone strata which character- 
ized the close of the Silurian era, it ended with one of the thick- 
est and most extensive sheets of shales known in American 
geology. With this complete change of sediment came also al- 
most as complete a change of the fauna. 
The geographical development of Appalachia introduces a 
large estuary pouring great quantities of fresh water and sed- 
iment into the Appalachian gulf from the rising New Eng- 
land area. The evolution of so extensive a water system in the 
northeast, must, in the first place, have tended to lower the 
temperature of the water. A large northern river flowing from 
a latitude as high as that of New England into a nearly en- 
closed gulf previously the seat of limestone sediment and the 
abode of coral building polyps, could not but cool the previ- 
ously semi-tropical waters and, to that extent, render them un- 
congenial to their previous tenants. Secondly, the consequent 
fouling of the Appalachian waters with a fine mud, must have 
contributed in no small degree to render them unfit for' the con- 
