GLACIERS OF PRINCE WILLIAM SOUND 757 



Climatic cycle was known to him, he assumed that each rhythm represented 

 the precession cycle. But this gives, as he himself has pointed out, what is 

 generally regarded as the excessive estimate of 20,000,000 years for a part of 

 upper Cretaceous time. Similar sedimentary rhythms, though generally less 

 regularly developed, have been noted in many formations, extending even into 

 the Algonkian. 



It is seen that the precession cycle does not appear to fit well to either the 

 late Pleistocene moraines of recession or to the Cretaceous shales. Hunting- 

 ton's work, by permitting us to consider climatic cycles of intermediate periods 

 and independent of precession, brings these observations into greater harmony 

 with other lines of investigation. 



It must not be forgotten, however, that recent work in radioactivity tends 

 to give far greater estimates to the duration of geologic time, and that it would 

 be premature to abandon the precession cycle as one of the still possible expla- 

 nations of these geologic rhythms, but the field of geologic theory is enriched 

 by the additional possibility that these recurrent changes are similar in nature 

 to those changes which have operated with pronounced effect in historic times. 



Dr. Ellsworth Huntington : To Professor Davis's criticism on nomen- 

 clature I would reply that the point as to the term "fiords" seems well taken. 

 The term "Alpine" is properly applicable to mountains like those of the 

 Taurus, which rise to a height of 10,000 feet and which contained glaciers 

 during the Glacial period. My use of the term applied not merely to rock 

 forms, however, but also to the wooded aspect of the region. We need terms 

 which describe not only form, but also the nature of the vegetation of a region. 



Meaning of the gorges : There may possibly have been an uplift whereby 

 the cutting of gorges was occasioned at the outlets of lakes Kara Viran and 

 Koghadeh. I saw no evidence of this, however, in the form of other young or 

 revived valleys such as would be occasioned by uplift. The material of the 

 broad valleys where the lakes lie appears to have been largely carried off in 

 solution through underground outlets. 



As to age of strands: The strands of the Dead Sea and Lake Buldur vary 

 greatly in age and in the amount of change which they have suffered. The 

 characteristics of each are sufficiently pronounced, so that it ought to be pos- 

 sible to identify them merely from the amount of weathering and erosion. It 

 is possible that sufficient study would enable us to estimate the age of the 

 strands in years by comparing them with the minor features which can be 

 definitely dated. 



TIDE-WATER GLACIERS OF PRINCE WILLIAM SOUND AND KENAI PENINSULA, 



ALASKA^ 



BY U. S. GRANT 



(Ahstract) 



The Alaskan coastline between the mouth of Copper River and Cook Inlet is 

 deeply indented by bays and fiords, the heads of some of which are occupied 

 by glaciers discharging into the sea. These have been mentioned in the reports 

 on this district and some of them were studied by the Harriman Alaska Expe- 



» Read by title. In the absence of the author. 



