RESUME AND FIELD NOTES. 
123 
carbonifere avec des assises de schistes mar- 
neux,' noiratres a la partie inferieure. Ces 
assises sont liorizontales tres-bien strati flees, 
le gres est friable dans les endroits exposes a 
l’air, et se laisse travailler difficilement a 
cause du grand nombre de fissures qu’ il pre¬ 
sente. On ne rencontre pas de fossile. A 12 
milles au sud du Fort Smith on a une couclie 
de bouille bitumineuse de 12 pieds d’epaisseur, 
avec des traces de fer oxide. En allant au 
nord du cote de Washington county, a 40 
milles du Fort Smith, on s’eleve successivement 
par des faibles gradins-[?] sur le calcaire 
carbonifere, ou mountain limestone , qui apparait 
alors avec des Produotus, P>dleroption et Tere- 
bratula, caracteristique de cette formation ; 
des assises de coal d’une epaisseur qui varie de 
2 a 12 pieds, se trouvent repandues dans 
plusieurs des comtes avoisinant. 
LesOzarkes etant entierement carboniferes et 
de couches horizontales, sont dus a les denuda¬ 
tions du group carbonifere. II n’y a que les 
monts de Little Rock au Hot et Sulf. Springs 
qui sont disloques et anterieur au carbonifere. 
A 30 milles au sud du Fort Smith, il y a 
une montagne isolee de 2,000 pieds de hauteur, 
nommee Sugar-loaf q t qui est reste comme une 
colonne, temoin des immenses denudations 
auxquels cette partie du pays a ete soumise 
aux epoques tertiares et quaterniares. Cette 
montagne et formee entierment du coal meas¬ 
ures, plusiers couches de coal out ete trouvees 
a la base et au milieu de cette montagne ; il y 
a souvent des assises de gres de 5 a 12 pieds 
d’epaisseur, alternat avec des marnes schisteux 
gris noiratre presentant des traces de charbon 
et qu'elques minces assises de calcaires ; les fos- 
siles y sout tres-rares, s’il y en a. 
A la riviere Poteau, le gres est tres-friable, 
par couches de 15 a 20 pouces, gris jaunatre 
avec des taches noires, bitumineuses ; et des 
nodules d’oxide de fer ; il a aussi des ripple- 
marks. 
Le 15 Juillet nous quitons le Camp Wil¬ 
son, pour traverser la riviere Poteau, et nous 
nousavancons de 9 miles au Camp No. 2, Ring 
bouse. Nous traversons une espece de marais 
avec canes cu bambous forme de terrain d'al- 
of carboniferous sandstone, with beds of marly 
shales of a blackish color in the lower portions. 
These beds are horizontal, and the stratification 
is distinct. The sandstone is friable in places 
exposed to the air, and is worked with diffi¬ 
culty on account of the great number of fissures 
which it presents. No fossils are visible. At 
twelve miles south of Fort Smith, we have a 
bed of bituminous coal twelve feet thick, with 
traces of oxide of iron. On going to the north 
in the direction of Washington county, forty 
miles from Fort Smith, we rise insensibly on to 
slight hills of the carboniferous formation, or 
mountain limestone, which then is found to 
contain shells of Productus, Bellerophon, and 
Terebratula, characteristic of that formation. 
Beds of coal, of a thickness varying from two 
to twelve feet, are found spread in several of 
the adjoining counties. 
The Ozarks being entirely carboniferous, and 
in horizontal strata, are due entirely to the 
denudation of the carboniferous group. The 
hills of Little Rock, at the Hot and Sulphur 
Springs, are the only dislocation anterior to 
the carboniferous. At thirty miles south of 
Fort Smith, there is an isolated mountain two 
thousand feet in height, called Sugar-loaf, and 
which has remained as a column, in witness of 
the immense denudations to which that part of 
the country was submitted in the Tertiary and 
Quaternary periods. This mountain is formed 
entirely of the coal-measures, and several beds 
of coal have been found at its base and in the 
middle. There are often beds of sandstone, 
from five to twelve feet in thickness, alterna¬ 
ting with schistose marls of a blackish grey 
color, presenting traces of coal, and some thin 
beds of limestone. Fossils are very rare, if 
indeed there are any. 
At the river Poteau, the sandstone is highly 
fossiliferous, with a bed fifteen or twenty inches 
thick, of a yellowish grey color, and contain¬ 
ing bituminous black spots and nodules of oxide 
of iron ; there are also some ripple-marks. 
July 15. —We left Camp Wilson and crossed 
the river I oteau, and we advanced nine miles 
as far as Camp No. 2, or Camp Ring. We 
here crossed a marsh overgrown with canes 
like bamboo, being an alluvial formation over- 
