322 TJie American Geologist. June, i89o 
San Angelo, the county seat of Tom Green county, has been 
built at the confluence of the Concho rivers, and contains at 
the present about 4,000 inhabitants. Its site has been very 
happily chosen. It lies in the beautiful and fertile valley of 
the Main Concho river, which at this place is not less than 
thirty miles in width. Blue ridges of Cretaceous hills bound 
the valley on the north and south, and the waters of the Main 
Concho river traverse it. This is the only town of any consid- 
erable size west of Ft. Worth and Dallas, and of great com- 
mercial importance for western Texas. It is the largest ship- 
ping point in the state for stock. A prominent wool market 
and its trade extends over hundreds of miles north, south, 
west, and east. It has very handsome public buildings, large 
commercial stores, banks, waterworks, ice factories, good week- 
ly papers, and is connected by the G. C. & S. Fe R'y with the 
easi 
Drainag-e and Topogrraphy. 
The North Concho river traverses the country diagonally 
from northwest to southeast. The Main Concho river from 
west to east. Spring creek and Dove creek from southwest to 
northeast, and the South Concho river from south to north. 
The Colorado river having a southeasterly course, drains, with 
its tributaries, the north-eastern portion of this country. The 
above mentioned rivers and creeks have an abundance of run- 
ning water during the entire year, and many of their tributa- 
ries not here mentioned are perennial streams. The rivers and 
creeks have their sources on the Staked plains and flow with 
an average fall of ten feet per mile. 
TWIN MOUNTAIN, 
From the Knickerbocker Road. 
X. Permian. 
Considering this, a glance at the accompanying map will 
show that the country is well drained. The topography of the 
section is easily understood, if considered in connection with 
