Geographic Features of Texas. — Hill. 17 
are scarps of elevation and faulting produced by the pushing 
up or falling down of the country upon one side or the other. 
It should not be forgotten, however, that every scarp and val- 
ley of stratification is necessarily the consequence of the ante- 
cedent disturbance or elevation of the earth's crust which 
raised the accompanying strata to their present inclined 
position, and the line of this original disturbance is an im- 
portant bearing upon the origin and evolution of the 
topographic features under discussion. South of the Colorado 
the western border of the Black Prairie is no longer a decliv- 
ity, but ends against an elevation — not of its own area, but of 
the region against which it abuts. 
The Balcones. 
This scarp, although apparently a continuation of the fore- 
going, is not related to it by origin or by direct connection. 
It is an important and conspicuous topographic feature in 
Texas. This feature has frequently been referred to by the 
writer as the Austin-New Braunfels non-conformity, for it is 
along its line south of the Colorado, that the rocks of the 
lower Cretaceous series which form the highlands of the Grand 
Prairie, dip so unconformably between those of the Black 
Prairie, or upper Cretaceous region, accompanied by faulting 
of several hundred feet. 
In traveling across the Black Prairie, the western border is 
terminated by what is apparently a low mountain system 
rising two or three hundred feet above it. Upon ascending 
this it is found to be surmounted by a level plateau — the 
scarp being the eastern face of a great monocline which marks 
the border of the Grand Prairie next to be described. The 
International railroad follows the foot of this escarpment from 
Austin to San Antonio, and the Southern Pacific follows it 
from that city westward to the Rio Grande. The topography 
of this feature was partially represented upon some of the 
earlier maps of Texas as a mountain system, especially on 
the geological map published by Dr. Ferd. Roemer in the year 
1842. The Spanish speaking people — ever ready with an ap- 
propriate descriptive geographical name — have called this 
scarp west of San Antonio "El Balcones." 
Why the Grand Prairie south of the Colorado should thus 
terminate in an eastwardly facing scarp, while the one north 
of that stream faces in a direction apparently opposite to it 
