Page:The National geographic magazine, volume 1.djvu/267

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The Rivers and Valleys of Pennsylvania.
211

The consequences resulting from readjustments of this kind by which their recent occurrence can be detected are: a relatively sudden increase of volume of the divertor and hence a rapid deepening of the course of the diverting stream, FE, and of the diverted, AF, near the point of capture; small side-streams of these two being unable to keep pace with this change will join their masters in local rapids, which work up stream gradually and fade away (Löwl, Penck, McGee). The expanded portion, ED, of the larger stream, CD, already of faint slope, may be locally overcome for a time with the increase of detritus that will be thus delivered to it at the entrance, E, of the divertor; while the beheaded stream, HB, will find itself embarrassed to live up to the habits of its large valley [Heim]. Geographic exploration

Fig. 16.
Fig. 16.

Fig. 16.

Fig. 17.
Fig. 17.

Fig. 17.

Fig. 19.
Fig. 19.

Fig. 18.

with these matters in mind offers opportunity for the most attractive discoveries.

18. Examples of adjustment.—Another case is roughly figured