10 Bnllclvi of Labomtorics of Doiison Univci'sity. [Voi. xii 



nearly due east and west. This Bladensburg valley was the 

 main axis of a small stream, tributary to the old Mt. Vernon 

 river, to which reference has already been made. It is evident 

 that the waters which cut out this old valley flowed toward the 

 West because to the East it heads in the rock divide, then 

 widens and deepens (so far as the rock floor is concerned) 

 toward the West. It was in one of the southern tributaries of 

 this valley that a col was cut down in opening up the new 

 gorge of the Wakatomaka. The filling in this Old Bladensburg 

 Valley is so deep that the tops of the hills immediately border- 

 ing the pre-glacial main valley have been entirely covered, and 

 the present appearance is that of a great valley whose sides are 

 the divides bordering the hydrographic basin of the old stream. 

 The appearance of greatness is so deceptive that when we first 

 came upon the view we were sure that we had found the long 

 sought for outlet of the middle Walhonding. But when we 

 found it heading out in the highest rock divide in this part of 

 the state, and saw, furthermore, that the present floor of the 

 valley is very high as compared with other valleys in the region, 

 we revised our conclusions and decided that its present great 

 width is due to the tremendous filling that it has undergone. 

 This filling consists of the usual deposits found in the glaciated 

 portions of the state — irregularly deposited boulder clay of 

 varying depth and composition. The floor of the valley as 

 now filled up is not level but is rolHng with here and there con- 

 siderable heaps t)f material as thougii left by icebergs stranded 

 on some point of rock higher than its neighbors. At the same 

 time the whole region is so completely covered with the debris 

 that it would seem as though the bulk of the deposition must 

 have resuked from the advance of the ice sheet into the valley 

 and all its tributaries. It is lo be noted also that this filling of 

 the Old Bladensburg Valley extends up to the very top of the 

 divide separating this drainage from that of the Walhonding. 

 But this is a feature that will be referred to later in another 

 connection. 



A clearer view of the Wakatomaka modifications, as well 

 as their relation to the Walhonding system, may be had from a 



