138 



L. E. HICKS — SOME ELEMENTS OF LAND SCULPTURE 



(weather carve) and a lower concave portion (water curve). Some land- 

 scape engineers have caught nature's hint and give a terrace the form 

 shown in figure 3, which' is at once more elegant and more solid and 

 durable than a slope in which the convexity is carried uniformly down 



Figure 4. — Unstable artificial Curve. 



to the base, as in figure 4. The latter is unnatural and unstable, while 

 the former is natural and stable. 



Reversed Carre*. — Tins combination of the weather curve with the ver- 

 tical water curve of erosion when carried out upon both sides of a struc- 

 tural block (as m a <> j>. figure 1), which is symmetrical and homogeneous, 

 will give the pair of reversed curves shown in figure 5, instead of the 



Figure 5. — Normal relief Form in an advanced Stage 0/ Base-leveling. 



simple convex weather curve db e, figure 1. Figure 5 is the normal 

 pattern of relief forms in a region of advanced land sculpture. The 

 summit b a b is a simple, typical weather curve. The talus of figure 1, 

 with its clear-cut structural angle, e c p, has been replaced by the vertical 

 water curve b c (figure 5), which is concave upward. 



Gilbert's "Exception" explained. — This same combination of weather 

 and water curves is the true explanation of the li exception " noted by 

 Gilbert* who states : 



" There is one other peculiarity f of bad-land forms which is of great significance, 

 hut which I shall nevertheless not undertake to explain. According to the law of 



Figi re 6. — Typical Profile of the drainage Slopes of Mountains. 



* Report oii the Geology of the Henry Mountains, pp. 122-123. 



t Figure 6, which is a reproduction of Gilbert's figure 54 (ibid., ]>. 116), shows an angle. Such 

 would be tin- actual result of intersecting water curves bui for tin- effed of weathering, which 



rounds oil' the angle and replaces it by a curve convex upward. 



