From introduction: In presenting this paper the writer has two objects in view. The first is to add to the general knowledge respecting the geology of this central district [Appalachian coal basin]. The groups determined in this region will be carried over the adjoining territory if they can be distinguished and they afford a type-section of the Coal-measures where they are probably best developed. The results are not put forth as final, but as representing the most probable conclusions from the observed facts.