OF ARKANSAS. 



115 



Fire clay and shale. 



50? 



~ 



* I 



L I 



Sandstone. 

 Pentrimital limestone. 



Shales, including an inch or two of coal, in 

 the cut below Cato's spring. 



sponges ; but less sym- 

 metrical, and without 

 any apparent porous 

 structure. They are, 

 most likely of vegetable 

 origin, and may, per- 

 haps, be referrible to that 

 obscure order of marine 

 plants, known under the 

 name of fucoides ; but, 

 if so, are entirely differ- 

 ent in form from any- 

 thing of the kind I have 

 ever observed before, or 

 seen described in any of 

 the works on fossil bo- 

 tany. 



In the collection of 

 W. Washburn, I saw 

 some fine specimens of 

 lepidodendrons, which 

 have weathered out of 

 some of the higher sand- 

 stones of the preceding 

 section ; and imperfect 

 specimens of the same 

 fossil plant were observ- 

 ed by members of the geological corps in the adjacent sandstone ridges. 

 This is a plant which occurs in the millstone grit, but more abundantly 

 at the base of the coal measures. 



It is a question of interest and importance, to determine whether any 

 portion of the upper sandstones and shales of Washington county can be 

 referred to the true coal measures ; since, in that case, there would be 

 hope of finding thicker and more valuable beds of coal in this county than 

 have yet been discovered. At present no coal beds are known of more than 

 18 or 20 inches ; except one, with a clay parting, in Mountain township, 

 on the head of the Illinois river, 6 or 7 miles east of Boonsboro, which is 

 about two feet thick; and those beds, at present known, in the immediate 

 vicinity of Fayette ville, in shales under the millstone grit, do not exceed 

 one foot. 



i i i i 



30? Archimedes limestone. 



Shales. 



Calcareous band, with pyrites-? 



Gypsiferous shale. 



Black shale with carbonate of iron. 



