DAVIS: KIVER TERRACES IN NEW ENGLAND. 



301 



more definite proof of this feature in the behavior of a meandering river 

 is found in the new edition (1900) of the Preliminary Map of the Mis- 

 sissippi (one inch to a mile), in which a red overprint indicates the new 

 position of the channel, as determined some fifteen years after the 

 previous survey (see especially sheets 14, 16, and 18). 



The same down-valley shifting of the meanders is seen in the enclosed 

 meanders of many rivers, typified in North branch of the Susquehanna, 

 Figure 8. This fine river has in- 

 cised its course beneath the up- 

 lands of northern Pennsylvania. 

 The upland spurs that enter the 

 river curves have been subjected 

 on their up-valley sides to a per- 

 sistent sweeping that is but little 

 less effective than that by which 

 the curved re-entrants between 

 the spurs have been scoured out. 

 The up-valley side of the spurs 

 have strong bluffs, as different 

 from their gentle down - valley 

 slopes as are the high lateral 

 bluffs that enclose the curves 

 from the gentle terminal slopes of 

 the spurs. It is noteworthy that in this case of a rock-walled valley, the 

 down-valley shifting of the curves does not seem to have been more 

 than fifteen or twenty times greater than the degrading of the river 

 channel in the latest period of valley trenching : while in the case of 

 terracing streams in drift-filled valleys, the first of these changes ex- 

 ceeds the second in a much higher degree. It may be further noted 

 that the North branch of the Susquehanna above Wilkes Barre seems 

 for some time past to have ceased deepening its valley, for narrow 

 double-curved scrolls of flood plain are now systematically added to the 

 outer end and the down-valley side of the spurs, as may be especially 

 well seen just above Tunkhannock, and as is indicated by the dotted 

 areas M M', opposite the under-cut bluffs, N N', Figure 8. 



Other examples of meandering valleys, exhibiting the systematic lateral 

 growth and down-valley shifting of the meander curves, might be 

 instanced ; a few of them are mentioned in my paper on the Drainage of 

 Cuestas (89). It is my hope to give at another time a fuller account 

 of this phase of river development, and then to show how satisfactorily 



Fig. 8. 



