136 THE JOURNAL OF GEOLOGY. 



being not more than thirty to forty feet. The outer moraine of 

 the East White River lobe, after following an upland tract west of 

 the West Whitewater northward for some distance, descends, 

 near Cambridge City, into the valley of the West fork of West 

 Whitewater, and after crossing this valley rises near Hagerstown 

 onto elevated upland. The outer moraine of the Miami lobe 

 also, in crossing Noland's fork, south-east of Cambridge City, 

 descends into and is developed in the valley as well as on the 

 bordering ridges. That the valleys were formed previous to the 

 deposition of this moraine, there can be no doubt, and being 

 made entirely in the drift, as noted above, they show clearly 

 that their excavation must be confined to the interval between 

 the deposition of the earliest drift sheet and that of this moraine. 

 The amount of erosion is several times as great as that accomp- 

 lished by the streams that have traversed this valley since the 

 moraine was laid down. The size of the streams which formed 

 them constitutes an important factor in determining the time 

 required in this excavation. That these interglacial streams 

 were not much larger than those now traversing this region, 

 seems probable from the fact that within a few miles north from 

 the sources of the present streams, the general slope of the 

 country becomes northward, so that drainage would naturally be 

 in that direction, instead of southward along the Whitewater. 

 The erosion here displayed seems, therefore, to indicate the lapse 

 of a longer interval between the deposition of the earliest drift 

 sheet and that of the outer moraine of the later drift, than the 

 time that has elapsed since the formation of that moraine. 

 How much of this interval preceded the silt deposition, it is 

 difficult to determine, because the outer moraine has concealed 

 the silt. Light upon this question should be obtained upon care- 

 ful study of the lower portion of the Whitewater valley and of 

 other valleys lying within the silt -covered district and outside 

 the moraine, but this line of study has not yet been under- 

 taken. 



Depression accompanied by silt depositio7i. The silt which is 

 found on the upland outside this moraine, has been discussed at 



