88 THE JOURNAL OF GEOLOGY. 



stream in Florida, hardly incised in the low coastal plain, illus- 

 trates the faint relief permitted in surfaces that stand but little 

 above their baselevel. The Colorado, in its canyon, is another 

 example of an early stage of development, but it possesses an 

 extreme intensity of relief because of the great altitude of its 

 plateau ; not an old valley, but a precocious young valley ; not 

 a vast work, except in our inappropriate human measures, but 

 the good beginning of a vast work. The Elbe above Dresden 

 offers illustration of a later stage than the three preceding ; it 

 has the beginnings of a flood plain, now on one side, now on the 

 other side of the river ; from which it is inferred that the deep- 

 ening of the valley has practically ceased, that the river is 

 graded, and that the slower process of valley widening is now 

 the determining cause of topographic change. 



Views in the Jura mountains would serve as examples of 

 adolescent forms, combining an interesting measure of conse- 

 quent and subsequent features ; but I have not yet succeeded in 

 finding any satisfactory photographs of this region. Features of 

 maturity, more or less advanced, are found in the retreating 

 escarpments of the middle Ohio valley^ or of the central denuded 

 region of Texas ; and again in the minutely carved ranges of the 

 central Alps. For yet older stages, it is difficult to find exam- 

 ples still in the cycle in which their old age was reached ; but 

 the plain of the middle Wisconsin river and the plateau of the 

 middle Rhine are ideally satisfactory illustrations of baseleveled 

 surfaces, one being an old plateau, and the other an old moun- 

 tain region ; although both have lately been brought into a new 

 cycle by elevation, allowing their rivers to cut narrow trenches 

 beneath their even surfaces. By selecting views in which only 

 the plain surface is seen, these examples make appropriate clos- 

 ing members of the series here described. At a later time, when 

 the complications of the cycle are in discussion, other views 

 showing the dells of Wisconsin and the gorge of the Rhine may 

 be presented, thus giving a new meaning to old examples. 



' Not the slopes of the young trench by which the Ohio now cuts across the Cincin- 

 nati plain, but the escarpment enclosing the plain many miles back from the trench. 



