486 



JOHN LYON RICH 



the valleys of swift streams the latter process will be relatively 

 rapid; in those of streams of low gradient, such as the master 

 stream we have postulated, the river may flow for long ages before 

 removing all signs of its former stages. 



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Fig. 7. — -An intrenched meander valley in which the stream, having reached grade 

 is beginning to widen the valley. Note that the upland between the loops keeps 

 practically its full height almost to the end. From the Versailles (Mo.) topographic 

 sheet. Contour interval 50 feet. 



Examples of streams which show features corresponding to 

 those just deduced are very numerous. For the earliest stage, 

 when intrenchment is just beginning, the Green River in Kentucky 

 (Fig. 6, Calhoun sheet, U.S. Geol. Surv.) is instructive. Here the 

 predominance of down-cutting over lateral cutting in the determina- 



