436 ELIOT BLACKWELDER 
comparatively easy matter, because of the complexity of the rock 
structure beneath. Elsewhere difficulties are introduced. The high 
plateaus between the Sherman arch and the city of Cheyenne are 
seemingly an easterly continuation of the peneplain, for their tops 
fy 
3 
ey 
Fic. 4.—Decayed granite cut by a basic dike. A feature of the Sherman peneplain 
surface. 
are at the proper elevation and do not seem to correspond exactly 
with the structure of the underlying rocks. However, the fact that 
the beds from which they have been carved are horizontal makes it 
