250 77^1? American Geologist,. April, i9oi) 
of the "fall line" in southern Georgia, where the piedmont plateau is 
succeeded by the coastal plain. Some of the author's observations and 
conclusions were presented by him in an article in this magazine for 
April, 1899. An excellent fire-clay industry in the Potomac division of 
the Lower Cretaceous outcrops along the "fall line," which crosses the 
state from Augusta to Columbus. This clay is used for the manufac- 
ture of pottery and fire-brick, and as an ingredient of wall papqj . 
w. u. 
Physiography of the Chattanooga District in Tennessee, Georgia, 
and Alabama. By Charles Willard Hayes. (Nineteenth Annual 
Report, U. S. Geol. Survey, 1897-98. Part II, pp. 1-58, 5 pis.) 
This report is in such a form as to be available to those who are 
not familiar with the principles and methods of the modern geographic 
school. Consequently it embi-aces a re-statement of many elementary 
principles, as well as an account of observed facts. The subject mat- 
ter of the paper is closely related to that of the author's previous pub- 
lications, "The Southern Appalachians,"* and "Geomorphology of the 
Southern Appalachians."! The latter papers dealt with the general 
physiographic development of the area of which the Chattanooga dis- 
trict is a small part, while the present paper is both a ♦ecapitulation 
of these writings and a more detailed development of the same sub- 
ject. 
In connection Avith his discussion of general principles, the author 
adds a new term to physiographic nomenclature. He confines the 
term monadnock to residuals rising above a peneplain well advanced 
toward reduction to base-level. He uses the term unaka to cover 
residuals in relief above a less advanced peneplain. The Unaka moun- 
tains of eastern Tennessee and North Carolina furnish both the type 
and the name. 
The Chattanooga district contains portions of all the five Appala- 
chian topographic divisions; Piedmont Plateau, Appalachian Moun- 
tains, Appalachian Valley, Cumberland Plateau, and Interior Low- 
lands. The author classifies the various rock types according to 
erodibility, and illustrates in a graphic way the relation of topographic 
relief to lithologic composition. 
The most striking physiographic features to be distinguished arc 
three peneplains. A Cretaceous and a Tertiary peneplain were de- 
scribed in "Geomorphology of the Southern Appalachians." In the 
present paper the author finds the Cretaceous peneplain in the Chat- 
tanooga district to be represented by the Cumberland Plateau. Far- 
ther study of the Tertiary plain, which is here represented by the 
Highland Rim, has led him to place its date as Eocene. Below this 
he distinguishes a third level, the Coosa peneplain, which he finds 
to be of Neocene age. 
*C. W. Hayes: Nat. Geog. Monograjihs, vol. I, No. 10, Dec. 1895. 
pp. 305-336. 
fC. W. Hayes and M. R. Campbell: Nat. Geog. Mag., vol. VL 
1894, pp. 63-126. 
