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Sian a ull 
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J. D. Dana on American Geological History. 329 
this, from the melting snows of the declining glacier epoch. 
The frequent absence of fine stratification, so common in th 
material of this upper terrace, has often been attributed to a 
glacier origin. 
According to this view, the events of the Post-terti eri 
in this country make ingle consecutive series, dependent 
mainly on polar or high-latitude oscillations :—an elevation for 
the first or Glacial Epoch ; a depression for the second or Lauren- 
tian Epoch ; a moderate elevation again, to the present height, 
for the third or Terrace Epoch. 
The same system may, I believe, be detected in Europe; but, 
like all the geology of that continent, it is complicated by many 
conflicting results'and local exceptions; while North Ameri 
as I have said, is like a single unfolding flower in its system of 
evolutions. 
There is the grandeur of nature in the simplicity to which 
we thus reduce the historical progress of this continent. The 
7 arts of the continents. | 
n deducing these conclusions, I have only stated in order the 
ts as developed by our geologists. Were there time for a 
More minute survey of details, the results would stand forth in 
bolder characters, 
The sublimity of these continental movements is greatly en- 
hanced when we extend our vision beyond this continent to 
(Other parts of the world. It can be no fortunate coincidence, 
that has produced the parallelism between the an 
will not wander, although the field of study 
é. 
___ In thus tracing out the fact, that there has been a plan or sys- 
Bo of development in the history of this planet, do we separate 
2 SECOND SERIES, VOL. XXII, NO. 66,—NOV., 1896. 
2 
