130 Bulletin of Laboratories of Deni^on University, [voi.xiii 



ing the stream valleys. Further cutting in the Logan develop- 

 ed easy slopes down which Sharon blocks are still creeping. 



And erosion was again retarded whenever encountering 

 the coarse phase of the Black" Hand conglomerate, the phase 

 that predominates in Perry township.^ 



Still another factor has had much to do, as already intimat- 

 ed, in producing the present drainage topography : These 

 conglomerate and coarse sandstone horizons lack homogeneity 

 in both vertical and horizontal sections. Since the maximum 

 thickness of either formation is not over 225 feet, the vertical 

 changes in texture are not of controlling importance ; but the 

 variations in horizontal extension is important. This control 

 is manifest in the short and disproportionately wide tributaries, 

 in the contraction and expansion of valleys, in the distinct vari- 

 ations in angle of slopes, and in the crenate form of divide. 



Therefore the fact that a tributary is as wide or even wid- 

 er than the major valley, and that a stream is flowing through 

 a narrow reach in a valley which broadens both up and down 

 stream, may or may not be evidence of drainage reversal. Such 

 a relationship of valleys, or of streams to their valleys, may be 

 the normal result of drainage development in the lower Carbon- 

 iferous. 



/ 



' 'In the central and western parts of Licking county the Black Hand forma- 

 tion is finer in texture and contains more thin layers ; this condition is noted in 

 quarries about Newark and Granville. 



