Geology of the Monongahela Valley. 59 



on the superincumbent strata, had raised the ranges of mountains 

 to their present elevation, after the rocks which form4hem had been 

 deposited in a horizontal and tranquil state. This general dip of all 

 the strata to the north and west, or towards the Ohio river is prob- 

 ably one cause of a greater fertility of the soil, and a more luxuriant 

 growth of trees and herbage on the north and west sides of hills than 

 on the south and east, a greater quantity of moisture being directed 

 to that side from the inclination of the strata. 



From the tops to the bottoms of the hills, in many places, in oft- 

 en repeated series, the sandstone strata alternate with beds of coal, 

 shale, recent clay slate, limestone, red, brown and white marl. For 

 instance, two or three beds of coal are found in one hill, alter- 

 nating with as many beds of sandstone, slate and shale. Where 

 the earth has been penetrated to great depths, the same series is 

 found to prevail below the surface, although the coal deposits are 

 separated by a greater amount of intervening strata than those in 

 the adjacent hills. On the western fork of the Monongahela, in the 

 neighborhood of Clarksburgh, a singular arrangement is observed in 

 the outlines of the hills. They have the appearance of being cut 

 into broad terraces, often for several miles in extent, thus 



Fig. 8. 



This appearance is produced by the immense beds of sand- 

 stone rock retaining their original position, while the softer deposits, 

 have been decomposed and washed away. Slides or avalanches 

 sometimes take place, in very wet seasons, which may also contrib- 

 ute to this remarkable appearance. 



The following section of the rock strata, near Clarksburgh, was 

 furnished by Judge Duncan, to whom I am indebted for much in- 

 testing and valuable matter, illustrating the topography and geology 

 of the Monongahela region. 



