CHAPTER III 
GENERAL CONSIDERATIONS AS TO GLACIERS 
Some of the field observations recorded in the preced¬ 
ing chapters have more than local interest in that they 
open theoretic questions and lead to suggestions bearing 
on the general subject of glaciers and their work. Certain 
of the suggestions have already been noted, as they seemed 
to belong to the discussion of the associated observations, 
but others may more appropriately be considered by them¬ 
selves and have been reserved for the present chapter. 
The general considerations already set forth refer to an 
annual cycle in the distal extent of tidal glaciers (p. 22), 
the production of features of shore topography by waves 
generated by the calving of icebergs (p. 69), anomalies in 
the variations of glaciers (p. 106), the origin of pitted 
plains (p. 54), and the origin and interpretation of hanging 
valleys (p. 114). The considerations to be presented in 
the following paragraphs pertain (1) to the broader char¬ 
acters of the surface of a glacier, (2) to the conditions af¬ 
fecting types of glacial sculpture, (3) to the conditions 
(195) 
