27 



ures in Champaign and Ularke counties, and they are also frequently 

 found to contain large deposits of human remains over which no 

 structure has been raised. The origin of these deposits is as much 

 involved in obscurity as that of the mounds and their contents. 



That portion of Mad river valley which lies in Clarke, Greene and 

 Montgomery counties has been so well described in President Orton's 

 reports contained in the "Ohio Greological Survey," that it would be 

 unnecessary to attempt the description here, except for the purpose 

 of presenting the subject as a whole and in a connected manner, hence 

 a brief summary only will be given. In the upper half of Clarke 

 county the topography is essentially the same as in Champaign coun- 

 ty, the only marked change observable being that the valley is gener- 

 ally narrower and the bordering hills higher. These side hills, like 

 those bordering the Ohio at Cincinnati, are in reality only the margins 

 of the general level of the country, and mark the limits of a former 

 period of erosion. In the latter instance the erosion has been ef- 

 fected principally through the Silurian limestone, while in the region 

 we are now describing it has taken place in the overlying drift depos- 

 its. The resemblance to hills is increased by the lateral channels ot 

 erosion which communicate with the main valley. Most of these 

 coinmunicating channels are short, steep gorges rising rapidly to the 

 general level of the plateau, while others traverse a large extent of 

 country and contain the present tributaries of the river. In this part 

 of its course the river traverses a large "cedar swamp," in which grows 

 the white cedar or Cupressus thyoides. This swamp and a smaller 

 one farther up the stream in Champaign county, are the only localities 

 in this part of the State where these trees are found native In the 

 peat bogs, especially those bordering Buck Creek, large trunks of the 

 red cedar are often met with several feet below the surface, but none 

 are found growing anywhere in the vicinity at the present day. 



If the surface deposits of Champaign, Clarke, Grreene and Mont- 

 gomery counties were stripped off and the rocky floor laid bare, 

 we should see a succession of limestone steps or platforms ris- 

 ing from the south and ascending toward the north-east of this 

 whole region. Across the northeastern part of Champaign and 

 Clarke counties would be seen the upper platform of this flight of 

 steps composed of the Helderberg limestone. Next in order would 

 be seen a broad platform ot Niagara rock, spreading over, probably, 

 the whole of Champaign and the greater part of Clarke counties. 



