614 THE JOURNAL OF GEOLOGY. 
in various parts of the globe.” The forty-eight years of con- 
stant study of the new discoveries in geology and testing the 
theory has shown it to be founded on fundamental truths of 
geology. The importance of this one, among the causes produc- 
ing the changes which have taken place in the history of organ- 
isms, is a sufficient reason for here making a lengthy quotation 
from the fourth edition of the Manual regarding the application 
of this theory. Speaking of the disappearances of life at the 
close of the Paleozoic, the following is written: 
‘““There was no break in the stream of life, but for the most part 
only seeming interruptions, and many of these owe their prominence 
in geological history to the culminations and declines of types that 
were in progress. But it was an epoch of relatively abrupt change, 
and if chiefly due to the progressive evolution of new species, as has 
been urged by some geologists, there must have been for the result a 
great acceleration in such change in consequence of the physical con- 
ditions produced by the orogenic disturbances. But the orogenic 
movements were local and the biologically transforming effects 
from such a cause should have been confined to the countries 
where these movements were in progress. The universality and 
abruptness of the disappearances cannot therefore be so explained. 
Very much is left for the destructive effects direct and indirect, that is, 
the exterminations attending the mountain making. 
“The causes of the exterminations suggested by the changes are 
two: (1) A colder climate over the land, and colder waters in the 
extra-tropical oceans, for the emergence of the eastern semi-continent 
of North America and of large lands in the other continents could 
not fail to lower somewhat the temperature of the whole globe. 
With a lower temperature, the currents from the north sweeping along 
the coasts would have been destructive to the marine species living in 
the waters. (2) Earthquake waves produced by orogenic movements. 
If North America from the west of the Carolinas to the Mississippi 
Valley can be shaken in consequence of a little slip along a fracture in 
times of perfect quiet, and ruin mark its movements, incalculable vio- 
lence and great surgings of the ocean should have occurred and been 
often repeated during the progress of the flexures, miles in height and 
space, and slips along newly opened fractures that kept up their inter- 
rupted progress through thousands of feet of displacement. The 
