CHAPTER IV. 
Remarks on the Geology from the Llano Estacado to Preston. 
General description of the country.—Red sandstone and gypsum.—Age of the Gypsum formation.—Absence of fossils.— 
Probable Carboniferous or Cretaceous age.—Gypsum of Nova Scotia in the Carboniferous.—Fort Belknap to Preston.— 
Section of strata.—Coal.—Carboniferous limestone.—Cross Timbers.—Cretaceous.—Loess. 
Tuts portion of the survey embraces a strip of country extending in a northeasterly and 
southwesterly direction, and over 300 miles in length. I cannot better introduce the few 
observations it is possible to make on the geology, than by quoting the general description of 
the section given in Captain Pope's report: 
‘The space between the eastern base of the Staked Plain and the Red river, at the parallel 
of 34°, is occupied by that portion of northern Texas drained by the tributaries of the Colorado, 
the Brazos, the Trinity, and the Red rivers. With rapidly-increasing advantages as you pro- 
ceed eastward from the Llano Estacado, this region is well timbered, well watered, and possessed 
of a soil of extreme fertility, capable of sustaining a dense population. The entire country is 
so gently undulating in its surface, and presents such an abundant and well-distributed supply 
of wood and water, that it can be traversed in any direction with trains of wagons, and is of so 
genial a climate that little choice of the seasons is considered desirable in undertaking an 
expedition through it. A great portion of the timber of the region intersected by the Colorado 
and its tributaries, along this route, is the mezquite, which, about thirty feet in height, and 
from six to ten inches in diameter, divides about equally with the prairie lands this entire 
district of country. The Brazos and its tributaries are better supplied with oak timber of a 
larger size, the country is more undulating, and the water more abundant. Immense coal-beds, 
of good quality, crop out along the valley of the river, and every advantage of soil and climate 
is offered to the emigrant. A military post (Fort Belknap) has been established "upon this 
stream, near the 33d parallel. But by far the richest and most beautiful district of country I 
have ever seen, in Texas or elsewhere, is that watered by the Trinity and its tributaries. Occu- 
pying east and west a belt of one hundred miles in width, with about equal quantities of 
prairie and timber, intersected by numerous clear, fresh streams, and countless springs, with a 
gently undulating Jürit of prairie and oak openings, it presents the most charming views, as 
of a country in the highest state of cultivation; and you are startled at the summit of each 
swell of the prairie with a prospect of groves, parks, and forests, with intervening plains of 
luxuriant grass, over which the eye in vain wanders in searçh of the white village or the stately 
house, which seem alone wanting to the scene. The delusion was so perfect, and the recurrence 
of these charming views so constant, that every swell of the ground elicited from the party 
renewed expressions of surprise and admiration.’’! 
A vivid contrast is here presented by this beautiful and fertile region with the arid plateau 
of the Llano; and the change is coincident with the marked variation in the configuration of 
the country. "The difference in altitude is not alone the cause of the change; the character of 
the soil is doubtless very different from that of the Llano; and this, with the number of streams 
giving abundance of water, and the climatic conditions incident to a lower level and greater 
proximity to the Gulf, are sufficient to explain this extraordinary fertility. 
! Report of Captain Pope, p. 9. 
