PAPERS ON GEOGRAPHY AND GEOLOGY 349 



which have such slight relief as to be scarcely recogniz- 

 able as divides. The lowland consists of flood plains, 

 low and level near the rivers, and terraces that are wide 

 but elevated only slightly above the flood plains. There 

 are two conspicuous hills upon the wide lowland between 

 the Wabash and Embarrass rivers, the Sand Ridge hill 

 east of the Embarrass just opposite Lawrenceville and 

 the Dubois hill just west of the Wabash river opposite 

 Vincennes, Indiana. 



The stratified rocks lying just beneath theToose mantle 

 rock consist of the McLeansboro formation of the Penn- 

 sylvania series. Although these upper layers of strati- 

 fied rocks lie practically in a horizontal position, the dif- 

 ference in the elevation of the upper surface of the solid 

 rock is much greater than the difference in elevation of 

 the upper surface of the soil. This is shown clearly by 

 the following table. 



SURFACE OF THE SOIL 



Highest point in Lawrence county 641 feet 



Lowest point in Lawrence county 391 feet 



Difference 250 feet 



SURFACE OF THE ROCK 



Highest known rock surface. 625 feet 



Lowest known rock surface 249 feet 



Difference 376 feet 



THE MAXTLE ROCK 



If the unconsolidated clay, silt, sand and gravel that 

 everywhere cover the solid rock were removed, the topog- 

 raphy would be much rougher than at present. The up- 

 land would present a topography differing but little from 

 the present one, although it would lie somewhat lower. 

 The lowland, however, would lie many feet below its 

 present surface. The Wabash river would flow from 

 100 to 175 feet below its present bed, and the Embarrass 

 would join it at as low a level. Brushy Fork and Muddy 

 creeks would join the Embarrass about 50 or 60 feet 



