334 M. JEFFERSON — LATERAL EROSION ON MICHIGAN RlVERS 



These bare strips, or "scaurs," as they are called in Scotland, lie 

 at points where the meandering stream is now close to the valley wall, 

 undermining it and causing it to cave and slip. Such points of contact 

 between stream and bounding valley bluff may often be seen alternating 

 to right and left in a view down valley, the up-valley aspect being wholly 

 of grassy slopes. This is because the downstream migration of meanders 

 causes a constant attack on the up-valley side of reentrant cusps, which 

 are therefore the especial site of scaur, while the downstream side of the 

 same reentrant watches the stream that once bathed its foot draw steadily 

 away — a process admirably described by Davis. Valleys like this are 

 typical of Michigan south of the Grand-Saginaw valley. Results of the 



Figure 1. — Scaur on the right Bank of the Lower Rouge. 

 The river carries off creeping waste as fast as it falls, and the banli retreats. 



uniform softness of the material in which they are cut are the rapidity 

 with which they are made, the tolerable grade of their course, and the 

 youthful slopes by which their flood-plains are everywhere bounded. 



The topographic sheets of the U. S. Geological Survey are not usually 

 accurate enough or detailed enough to show the character of these valleys 

 or even the meandering of the streams that carve them, and the topog- 

 raphers have not recognized the existence of these forms. It is appro- 

 priate to their slight recognition that what I have called scallops in the 

 bluff have no accepted name among writers on the siibject, The sheet 



