Pcneplai)is of the Ozark Highland. — Hershey. 31 
they soon rise up to form the foot-hills of the Boston moun- 
tain, and just where the dissected peneplain leaves off and the 
mountain spurs begin to be monadnocked on it, is not every- 
where easy of determination. 
Within the Boston mountain the Tertiary base-level is 
hardly recognizable. The valleys on the southern slope are 
cut through the interval between the Cretaceous and Tertiary 
base-levels and far below the latter. Those north of the di- 
vide are not so deep and hardly reach the level of the Tertiary 
peneplain. But in emerging from the mountain on the north, 
the newer peneplain is soon encountered, in one of its most 
typical and unmodified forms, at an average altitude of about 
1,700 feet A. T. Standing on a spur of the Boston moun- 
tain, one may look northward for many miles over a country 
distinctly lower and apparently a regular plain upon which 
rise the outliers of the Coal Measure strata. The plain is 
pretty thoroughly dissected by narrow basins and still nar- 
rower canyon valleys. In places there are long, narrow, even 
crested ridges as in south Arkansas, but usually the drainage 
systems are of a perfect dendritic type, and the ridges branch 
and re-branch like the limbs of a tree. Near the White river, 
the whole country is cut up into a complex of very narrow 
ridges and gorge-like, V-shaped valleys, some of which are so 
deep that the intervening remnants of the strata are called 
mountains ; notably the Eureka mountains in Arkansas, and 
the Carney mountains in Missouri. The same topography 
prevails along the Osage river and, indeed, belts of such ex- 
tremely rough country follow all the main streams in the 
Ozark plateau region. 
That the general upland surface from the northern base 
of the Boston mountain to the Missouri river represents one 
and the same dissected peneplain needs no elaborate demon- 
stration. Where the plateau is trenched by deep valleys and 
even such broad basins as that along the White river in Mis- 
souri, the "mountains" on either hand correspond in hight. 
The most broken portion of the Ozark plateau, when looked at 
from a distance, appears like a plain of remarkable evenness. 
Along the main divides, such as that followed by the S. L. & 
S. F. R. R. from Lebanon to the Boston mountain, erosion has 
not been active, and the streams have not cut deep valleys into 
