lS-i T. C. Ghamberlin — Diversity of the Glacial Period. 



of the Ice age. This, it seems to me, holds good under any 

 form of the aqueous hypothesis of thuse silt formations that 

 is consistent with the phenomena. If they are attributed to 

 wind action, the aridity and the combination of conditions 

 necessary for the accumulation of the silts make the presump- 

 tion of disappearance of the ice equally great. 



Subsequent to this period, on the theory of elevation, there 

 must have been another uplift at the north sufficient to cause 

 the ice to readvance to points as far south as the first advance 

 in certain regions, and within 300 to 500 miles of the first 

 advance in others. 



Now an elevation sufficient to produce glaciation as far south 

 as 38°, followed by a depression sufficient to permit silts to 

 accumulate 7° north of this, followed by another elevation 

 sufficiently great to cause ice to advance to like degrees of 

 latitude, in the main, seems to me a sufficient change in the 

 great agency of the time and a sufficient orographic movement 

 to justify the distinction of separate epochs. So far as I can 

 see, nothing less than these extraordinary oscillations are suffi- 

 cient to explain the phenomena, and to these must be added 

 minor oscillations of very considerable moment. For myself 

 the phenomena of low altitude deposition seem so great and 

 so completely demonstrable as to be fatal to the hypothesis. 

 But if not, the very multiplication of overlapping sheets 

 and marginal moraines signifying halts and advances, that is 

 appealed to in the endeavor to weaken the evidence of two or 

 more epochs, bears in precisely the opposite direction when 

 the demonstrable conditions of such halts and advances are 

 duly taken into consideration. 



In the matter of the " fringe," Professor Wright's statement, 

 " The fact that the oldest part of the glaciated region ' is not 

 bordered by a definite terminal moraine, but ends in an 

 attenuated border ' is only another way of stating the fact 

 which Lewis and I began to urge upon the attention of the 

 public ten years ago during the early part of our investiga- 

 tions," is unwarranted and tends to confusion historically and 

 scientifically. The chief questions regarding these phenomena 

 were squarely and broadly before scientific readers before 

 Professors Lewis and Wright urged their single view of one 

 variety of the phenomena. But that is a trivial matter. On 

 the contrary, the confounding of the phenomena designated 

 and interpreted as- a " fringe " with the phenomena of the 

 attenuated border is a serious source of error. The phenom- 

 ena are not only not equivalents, but they stand in some 

 measure as antitheses. There are four classes of facts to be 

 distinguished. 



