8o THE JOURNAL OF GEOLOGY. 



ing of the valleys progresses even slower than the slow wasting 

 away of the hill tops ; the relief fades ; the load offered to the 

 streams lessens. The rainfall slowly decreases as a normal con- 

 sequence of decrease of altitude ; the ratio of river discharge to 

 rainfall decreases ; the small headwater branches shorten and 

 dwindle away ; the close adjustment of stream to structure is 

 more or less lost, especially by the larger rivers, which meander 

 and wander somewhat freely over the peneplain of denudation. 

 Extreme old age or second childhood is, like first childhood, 

 characterized by imperfect work ; activities that were undeveloped 

 in the earlier stage having been lost in the later stage. 



All this should be so carefully imagined and so frequently 

 reviewed that the orderly sequence of changes may pass easily 

 before the mind. The mind should come to be in so close a sym- 

 pathy with the progress of the cycle as to forget human measures 

 of time and catch instead the rhythm of geographical develop- 

 ment ; even to the point of almost wishing to hurry to one place 

 or another where some change of drainage or of form is immi- 

 nent, for fear of failing to be in time to see it in its present stage. 



Shore lines. — While the subaerial forces are denuding the sur- 

 face of the land, the waves are beating on the shore and reducing 

 the land mass to a submarine platform. They begin their work 

 on a level line, contouring around the slope of the land mass as 

 it is offered to them. The contour is simple if the sea lies on a 

 rising sea bottom, evenly spread over with sedimentary deposits ; 

 the contour is irregular if the sea lies on a depressed land, more or 

 less roughened by previous denudation. The waves of a great 

 ocean work rapidly on a leeward shore, especially if it has a steep 

 slope and if its rocks are not too hard : but if the descent to 

 deeper water is very gradual, the waves may for a time spend 

 their force chiefly on the bottom, building off-shore bars with the 

 material they gather up, and thus deepening the water outside of 

 the bars for a better attack on the land later on. The shore line 

 is generally simplified, as the attack advances, but it may for a 

 time become more irregular if the waves are strong and the land 

 structure is of diverse resistances. Its changes deserve as care- 



