* Geology of Upper Illinois. 149 
Camp-rock, whose direction and dip it likewise exactly imitates. 
The opposite side of the river, (at E,) moreover, offers us appa~ 
rently the entire series of slates, shale, and coal, which overlie the 
sandstone in the Swanson ravine, though the coal has as yet been 
fairly laid open only at two spots, Dand E. At both these places, 
the thickness of the coal-stratum is four feet. No doubt, therefore, 
can reasonably be entertained of the unbroken continuity of the 
coal across section eleven to the Little Vermilion on sections two 
and thirty-four. The southeast angle of the latter section touches 
the northwest corner of the former, as the sectional maps of the 
region will show. In following the river above HE, no farther tra- 
ces of the coal-rocks, are discovered. On the contrary, the mag- 
nesian limestone soon takes their place and forms the bed and 
banks of the Little Vermilion, and of its tributary, the Toma- 
hawk. 
Having satisfied myself of the general direction of the coal 
north of the Tilinois, it became a matter of interest with me to 
learn whether it obeyed the same law in an opposite direction, viz. 
in its extension towards the southeast. That this is the fact soon 
became apparent. The bluff on the south side of the Illinois, a 
little east of where the Big Vermilion enters, exhibits the same 
formation as Camp-rock. But no rocks manifest themselves in 
the line of direction from this place, until we reach the banks of 
the Vermilion at I, near Vermilionville. Here we recover the 
coal in the bed of the river, presenting its characteristic thickness, 
dip, and leading associates, with the exception of the underlie of 
sandstone, which, if existing, is concealed by loose materials and 
soil. The coal has the same thickness as at the mouth of the 
Swanson ravine. 
As my travels were extended no farther in the direction of the 
outcrop, I can only state what I was able to learn from others re- 
specting its course beyond Vermilionville. Abundance of coal is 
said to occur at several points for ten or twelve miles up the river, 
all of which may reasonably be considered as belonging to one 
and the same stratum. Indeed it is not impossible that future re- 
searches will prove the extension of the present outcrop quite 
across the country, even to the Wabash, in Indiana. 
The coal at Vermilionville is situated directly in the bed of the 
river, on its west side, at the base of a very steep portion of bluff, 
which is at least seventy-five feet high. It consists of five or six 
