194 REVIEWS 
where the conditions are more or less simple, with a view of establish- 
ing principles which may be used in regions of greater complexity. 
The region concerned is situated in southeastern Tennessee, north- 
eastern Alabama, and northwestern Georgia. It is bounded by the 
meridians of 84° 30’ and 86°, and by parallels of 34° and 36°, and 
comprises nearly 12,000 square miles. 
The problems considered are as follows: (1) The forms assumed by 
maturely adjusted streams in a region where the strata are faulted and 
folded, and where metamorphism has so affected the rock that the 
original differences have been diminished, leaving a somewhat homo- 
geneous series; (2) the forms assumed by streams when the strata 
- are practically horizontal, and where the beds vary greatly in hard- 
ness; (3) the processes by which consequent drainage in a region of 
folded strata is transformed into subsequent drainage, with the devel- 
opment of anticlinal valleys and synclinal ridges; (4) the present alti- 
tude of former base-levels and the determination of the deformations 
which the region has suffered in recent geological time. These prob- 
lems are considered under two main heads, namely, “‘Geomorphology ” 
and ‘‘ Geomorphogeny.”’ 
The Chattanooga district embraces a part of each of the five natural 
divisions into which the southern Appalachian province has been 
divided by Powell." Within this region Hayes finds three types of 
topography: (1) The Western type, including the Cumberland plateau 
and the Highland Rim, a part of the interior low lands; (2) the Cen- 
tral type, and (3) the Eastern type. 
(1) The first or Western type is separated from the other divisions by 
the Cumberland escarpment, which forms the eastern boundary of the 
Cumberland plateau. In the northeastern portion of this district streams 
have hardly begun to cut in the plateau, while to the south and west 
only remnants of the plateau remain, each remnant retaining the char- 
acteristics of the original highland. The plateau is about 1800 feet 
above sea level, the Highland Rim about 1000 feet, while the low lands, 
which stretch northwestward to the Ohio River, have an altitude of but 
600 feet. Thus it is seen that the Highland Rim is a terrace between 
the Cumberland plateau and the lowland. (2) The Central type is 
that of the Great Valley, in which there are three levels or -sets of 
levels. The valleys of the Tennessee and the Coosa rivers are from 
600 to 700 feet above sea level. One series of valley ridges reaches 
 Physiographic regions of the United States: Nat. Geog. Mag., Monograph No. 3. 
