1877.] Catastrophism and Evolution. 457 
feet of limestone, for the most part quite free from land-detritus, 
accumulated with all the evenness and regularity which the most 
ardent uniformitarian could ask, suddenly followed by an equal 
amount of pure land-detritus almost free from lime, This sud- 
den change of sediment simply means a sudden physical change, 
either a cosmical one which recorded itself as a cycle of climate 
productive of great erosion, or a terrestrial change resulting in 
such great disturbance of distant land and sea areas as to cause 
new climate or new avenues of drainage, or some remote coast 
disturbance which brought about a revolution of oceanic currents, 
In either case the sudden change, both at the beginning and end 
of the quartzite period, and the vast scale of the deposit, means 
a change of rate in the current operation of nature, and an enor- 
mous change of rate. The abrupt passage from a period in which 
little or no land-detritus has entered a sea for millions of years 
_ to one when it pours in with relatively marvelous rapidity is cer- 
tainly not uniformitarian. This phenomenon of sudden change 
in the broad petrographical features of a composite group of 
Strata is equally true of each sudden break, of which the western 
Paleozoic has six. Recall that the bottom of all this ocean was 
a former continent, that along the east the continent went down 
gradually, by considerable steps it is true, but still by periodic 
and, perhaps, gradual subsidences.. If the uniformitarians can 
derive any comfort from Eastern America, —and I suppose they 
justly may, — they are welcome to it. The rate of subsidence in 
the east, although not unlikely to have been catastrophic as re- 
gards the life of the disturbed region, looked at broadly may be 
called uniformitarian. That on the west was distinctly catas- 
trophic in the widest dynamic sense. 7 
Let us pass now to a remarkable chapter of events which 
closed the Palæozoic ages. What is now the eastern half of the 
Mississippi basin had through the coal period often extended 
itself as a land mass as far west as the Mississippi River, and had 
as often suffered subsidence and resubmergence. To the west, 
however, still stretched the open ocean, which, since the begin- 
ning of the Cambrian, had, with a single exception, never been 
invaded by land. At the close of the Paleozoic the two border- 
ing land areas of Atlantis and Pacifis, since the beginning of the 
Cambrian permanent and perhaps extended continents, began to 
sink. They rapidly went down, and at last completely disap- 
peared, their places being taken by the present Atlantic and Pa- 
cific oceans, while the sea floor of the American ocean, which had 
