Remarks on the Geology of the Concho country. 75 
small pebbles, the immense width of the valley of the main Concho 
river, the floor of which is the deposits of older formations with 
an opposite dip, the same level of the Lower Cretacic buttes and 
escarpments bounding the valley on either side, and the whole ap- 
pearance of the country prove conclusively that it owes its topo- 
graphy to denudation, and that aerial currents had comparatively 
little to do with its present surface appearance. Such conglome- 
rates as seen along the rivers of the Concho country often fifty 
feet high could onby have been formed through the immense pres- 
sure of vast volumes of water in channels with little fall. 
Fig. 2. Profile of the North Concho river, '_• nnlr below San .1 
l. Limestone conglomerate. '.',. River silt. 
•i. Yellow inagnesian limestone. 4. Red and blue clay. 
As mentioned before this enormous denudation has hud hare 
the limestone deposits, clays and sandstones of every quality and 
color, representing various geological ages. Beginning in the 
western part of Tom Green county, the middle Concho river, 
having its source on the foot of the "staked plains" with an 
easterly course, crosses the different strata of the Comanche 
series, the probable Jura and Trias of Marcou, the Permian of 
Boll, Cope and others, and on reaching Concho county lias un- 
covered the Carbonic rocks. 
Near the top of the 1'ermian exposed at lien Fielin on the bank 
of the Middle Concho river lies a deposit of an argillaceous d 
nesian limestone of a yellowish color containing a number of well 
preserved fossils enumerated in the formerly mentioned article, 
