Geology of Upper Illitiois. 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, D and 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 Yermilion 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 E, 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 Illinois, 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 



