EROSION AND ITS SIGNIFICANCE. 117 



ing [e.g. Colorado, Utah, Arizona, and California], To the 

 case of the New Zealand Alps and the Californian Sierras 

 reference will be made later. 



A personal experience may perhaps be of interest in this 

 connection. During a great number of cross-country 

 journeys undertaken some years ago in New England (New 

 South Wales), the writer had observed the existence of a 

 magnificent plateau level varying from 3,000 to 3,400 feet 

 in height. One peculiarity of this grand land surface lies 

 in the fact that it is separated into a northern and a 

 southern portion by a plateau about 1,000 feet higher, the 

 two surfaces being connected by long rambling spurs whose 

 bases are not arranged after any regular pattern. Further- 

 more, wherever examined the lower plateau was observed 

 to be dissected by very broad and shallow valleys, as to its 

 central portions, and by deep profound canons on its eastern 

 (and western) portions. Various other plateau remnants 

 also diversified the main surface, their heights varying from 

 200 to 1,200 feet above the general level. Ridges and 

 peaks likewise rose from these higher plateau blocks. The 

 walls of the broad plateau valleys were rarely rectilinear, 

 but were interrupted by jogs and large re-entrants. In the 

 year 1903 these surfaces were described as the products 

 of several cycles of erosion. 1 



In 1908 the writer accepted an invitation from Dr. G. K. 

 Gilbert to visit the Sierras of California in connection with 

 the question of the efficiency of ice as a powerful corrasive 

 agent. The trip was carefully planned by him so as to lead 

 the observer gradually to a scenic and physiographic climax 

 in the Yosemite National Park. The way led first across 

 the Great Californian Valley to Shafer via Fresno, thence 

 up a fork of the San Joaquin to the Upper Evolution Valley 



1 " Tertiary History of New England," Rec. Geol. Surv. N.S. Wales, 

 1903, p. 140. 



