28 
GEOLOGY 
country of the survey between the Lower Cross Timbers and the Elm Fork of Trinity river, and 
the sources of the Clear Fork of the Rio Brazos. 
On different points of the clilfs of the Rio Brazos, especially in the neighbourhood of Fort Bel- 
knap, several coal-beds outcrop, and show the richness of this coal-field of Texas. The Carbo- 
niferous rocks of the Rio Brazos are connected with those of the Arkansas river, being covered 
only for a width of thirty miles by the Cretaceous formation at Red and Trinity rivers ; and as those 
of Arkansas continue without interruption further north than the river Des Moines, in Iowa, it is 
evident that the immense coal-field west of the Mississippi is fully equal to that on the east of this 
river , and that the population of the western prairies will have at hand large supplies of this pre- 
cious mineral. Besides the coal, the presence of which upon your route is of immense advantage 
for the construction of a railway , the Carboniferous rocks present excellent sandstone for the con- 
struction of bridges and embankments, iron in abundance, and black slate. 
The upper part and the headwaters of the Rio Brazos are situated on the rocks of the Trias''). 
This important formation remained unrecognized (some regarding it as Carboniferous, and others 
as Lower Silurian and Cretaceous) until my exploration of the Canadian. Dr. Ferdinand Roemer, 
in his exploration of the part of Texas that surrounds the German settlements of Fredericksburg 
and New Braunfelds, had thought that he recognized the Triassic rocks; hut he cites them with 
hesitation^). Hitchcock, in his report to Capt. Marcy on the Red river exploration, thinks justly, 
from the sections of Dr. Geo. G. Shiimard, that this formation, which he calls Gypsum formation, 
is not Carboniferous ; but he does not know exactly to what geological epoch it belongs s)- My 
survey along the Canadian river, and yours, show clearly that the Triassic rocks rest upon the 
1) 1 have since used the more general expression of iVew lied Sandstone formation, to designate all 
the strata in America that lie between the Carboniferous formation and the Jurassic rocks (See: Resume 
Explicatif dune Carte Geoiogique des Etats-Cnis, etc., page 81)4.). The beds of the same age in Europe 
are known by the following names: Permian, Magnesian limestone, Todtliogendes, Zeehstoin, Gres \osgien 
and Trias. The Trias is subdivided in Germany, Switzerland and France into throe principal groups 
called: Bunter Sandstcin (Gres Bigari-e), Muscheikalk (Conchylien), and Keuper (Marnes Insees). 
2 ) Rtemer says: «Tho existence of the Triassic formation, in Texas, has not been distinctly recog- 
nized. But it is possible to suppose, from some remarks found here and there in the Journey of Fal- 
coner (Antes of a Journey through Texas and Aeic Mexico in the years 1841 and 1842, by Thomas Fal- 
coner, in the Journal of the Royal Geograph. Soc. of London, vol. XIII, pag. 210; London, 1843.), that 
he met with the Triassic rocks at the headwaters of the Red river. This traveller speaks of finding on 
the borders of Red river, to the west of the river Wishitaw, very extensive beds of a red sandstone in- 
tercalated with fibrous gypsum. He adds also that ho had already observed, west of the Cross Tim- 
bers, the water and sand of the rivers and creeks that he had crossed, to bo of a deep red color, 
and that all the stagnant and even the running water contained much salt. This red color of the rocks 
at the head of the Red river (giving it doubtless its color and its name) , the salt and the beds of gy [i- 
sum found there, appear to synchronize this formation with the Bunter Sandstein of Europe. But a 
synchronism founded solely on petrographic characteristics, without any knowledge of the superposition, 
or of the fossils, cannot be confidently relied upon#. (See: Die Kreidebildungen ron Texas, von F. Roe- 
raer, pag. 6.) 
3) Sec: Exploration of the Red river of Louisiana in the year 18,53, by Capt. R. B. Marcy. Appen- 
dix I). Geology: Notes upon the specimens of rocks and minerals collected; by Ed. Hitchcock, pag, 168, 
Washington , 1853. , ^ 
