HIGH PENEPLAIN 
I2 3 
ference rests partly on the trends of structure lines deter¬ 
mined by the Canadian Geological Survey in neighboring 
parts of the continent, partly on the trends of the straighter 
valleys and channels of the region itself. 
From this complex the pre-Pleistocene topography was 
developed by erosion. The only constructional forms we 
saw which might have antedated the Ice Age were a few 
volcanic cones. The system of relief was related to three 
known base-levels. The plane of the first is now high in 
air, above some of the mountains and among the peaks of 
others. The second is not far from present sea-level, and 
the third is below sea-level. 
The High Peneplain. — The uplands of the mainland 
are remarkably uniform in general height over large areas, 
not indeed presenting plain surfaces, but either exhibiting 
harmony of crest lines, despite profound and general dis¬ 
section, or else occupied by numerous small shallow val¬ 
leys, which are strongly contrasted with the deep steep- 
walled trenches of a less complete dissection. These 
features can be most readily presented in connection with 
some of the accompanying illustrations. Figures 3, 61, 
62, 63, 75, and 77 were drawn from photographs by the 
Canadian Boundary Commission. 
Figure 61 shows the upland topography north of the 
western end of Cross Sound. (The reader can identify 
the locality on the map, page 120, as the third cape west 
of the mouth of Glacier Bay.) We stand on a summit 
above Cape Spencer, and look northwest. At the left is 
the Pacific Ocean; in the center distance, the end of 
Fairweather Range (the nearest high peak being La Pe- 
rouse, 10,750 feet); at the right, Brady Glacier, its foot 
separated from Taylor Bay by a gravel strand. Between 
us and the base of the mountains, 18 miles away, are a 
series of hills somewhat uniform in height. The higher 
points (as we learn from the Commission’s contour map) 
