DESCRIPTION OF THE COUNTRY. 51 
the city, are found sandstones and limestones of the carboniferous period. ‘‘ Here begins the 
fine coal-basin of Arkansas which" * * * ‘our survey traversed from the vicinity of 
Little Rock to Delaware Mount, a distance of several hundred miles; coal being found almost 
everywhere from Petit Jean mountain to Coal creek and the Shawnee mountains, It forms a 
vast reservoir for the sustenance of industry and commerce along the whole line of the Pacific 
railroad. This carboniferous basin contains, in addition to the coal, an abundance of excellent 
sandstone for building bridges and embankments, good beds of limestone for the manufacture of 
lime, and also iron. Artesian wells will give an immense supply of water for agricultural and 
other uses, and it may be predicted that this region will be one of the richest portions in the 
southern States of the Union.”” 
From the Shawnee village to Little river there is excellent sandstone. Delaware Mount is 
formed of upheaved beds of carboniferous limestone, affording building material and quick-lime. 
After passing this ridge, we leave the carboniferous group and enter upon the new red sand- 
stone or trias. This formation is four or five thousand feet in thickness, and its various strata 
are traversed upon our route westward, except among the mountains where we rise above it, for 
more than one thousand miles. Mr. Marcou establishes, provisionally, “three principal divisions 
in these rocks." The lower group is composed of red and blue clay at the base, and red sand- 
stone above. It is some two or three thousand feet in thickness, and forms the surface of the 
country from Topofki creek to Rock Mary. In consequence of the prevalence of clayey soil, 
nearly the whole of this region is well watered by numerous rivulets, producing a bountiful 
fertility of forest and meadow. The sandstone upon this section is frequently coarse and 
friable. Quarries of good building stone may occasionally be found, though it is probable that 
bricks formed of the argillaceous clays would afford an economical and more durable material 
for masonry. 
‘€ The second group, or middle division’’ of the trias, ‘‘is formed of beds of red clay, con- 
taining very often immense masses of white gypsum, amorphous, furrowed with veins of crys- 
tallized gypsum, with interposition of strata of magnesian or dolomitic limestone, and frequently 
beds of rock-salt or saliferous clay are found superposed upon the gypsum. The height of the 
beds in this middle group is about fifteen hundred feet. We met with it on our route from 
Rock Mary to the Arroyo Bonito or Shady creek, with the exception of two points, where the 
direction taken by our expedition, near Camp No. 31, crossed strata of neocomien, and at Ante- 
lope Hills whitish-gray sandstone, which belongs to the upper division of the trias." The 
mineralogical characteristics of the group are of considerable importance. The sandstones upon 
this section occasionally exist in isolated masses, and appear like lofty colonades of some 
ruined city, and in many places have sufficient hardness and durability for embankments and 
bridges ; the dolomite produces an excellent hydraulic lime; the gypsum exists in vast quan- 
tities, and may become valuable for exportation, and the salt will be useful for the inhabitants 
of this region. With the exception of the well-watered and wooded valleys leading to the 
Washita, the soil of this region is deficient in clay. Hence, the numerous arroyos leading to 
the Canadian, and the Canadian valley itself, are sandy; and many of the little rivulets, 
started into existence by occasional heavy rains, soon become dry from the percolation of the 
water to the substrata of clay some feet below the surface. By common wells this reservoir 
of water could easily be reached, and made available for the purposes of a railroad, or for set- 
tlements. Nature has planted upon the sandy borders of the streams of this region the plum 
and the grape. The soil seems admirably adapted to their growth. 
“The third division, or upper group" of the trias, ‘‘is subdivided again into two parts. 
The lower is formed of thick beds of whitish-gray sandstone, often rose-colored, and even red; and 
the upper consists of beds of sandy calcareous clay of very brilliant colors—violet, red, yellow, 
and white—in a word, of variegated marls,’’ like “the marnes irisées of France, or the varie- 
gated marls of England.’’ ‘‘ These rocks having very little consistency, have been carried away 
almost everywhere by denudations. Itis only where they are capped by the jurassic strata that 
