456 Catastrophism and Evolution. [ August, 
That depth and the full accumulation of beds were arrived at by 
successive subsidences of the sea bottom. The Primordial or 
earliest Paleozoic along the eastern shore shows evidence of shal- 
low water, which deepened by the occasional sinking of the sea 
floor. This periodic subsidence went on through the whole Pa- 
leozoic time, influencing the Appalachian region, and during the 
whole coal-bearing period affecting the sea bottom as far as Kan- 
sas. Shallow-water evidences are common up to the Carbonifer- 
ous, after which successive low-level land areas repeatedly occu- 
pied the east half of the present Mississippi basin. 
This immensely long history of periodic but general subsidence 
was broken in the northeast by several sudden uplifts, in which 
_the sea strata were so disturbed and inclined that the succeeding 
beds rested on them unconformably, and in one instance the 
Green Mountain range was upheaved. The general law on the 
east side of the Pala-American Ocean has been the continual in- 
pouring of sediment from Palæ-Atlantis, subsidence of sea bot- 
tom, repeated a great number of times, and only locally varied 
by dislocation and uplifts. A very limited but not unimportant 
chapter has just been added to the American rock record by the 
geological exploration of the fortieth parallel; it is the mode of 
deposition of the Paleozoic rock in the Western United States. 
Passing now to the western side of the ocean, we have again 
the same enormous thickness of thirty or forty thousand feet of 
Paleozoic beds, but from bottom to top no evidence of disturb- 
ance, only uniform proof of deep oceanic deposition. In other 
words, the two sides differ: one went down by gradual and suc- 
cessive subsidence; the other at once sank so as to form a pro 
found ocean; which, from beginning to end of the vast Palæozoic 
age, received in its quiet depth the dust of a continent and the 
débris of an ocean life. I do not say that the western ocean bot- 
tom never suffered further subsidence. I only assert that be- 
tween the two sides the difference of rate was simply immense. 
In keeping with the minor and slight movements of subsidence 
in the east are the changes in the materials of the gatherimg 
strata, which are found to vary continually. Here again the 
contrast between the east and west is marked. All the Palæo- 
zoic series in the west consist in the main of a few broad changes 
between quartzitic and limestone beds, both giving evidence 0 
deep-sea deposition. By way of illustrating these changes © 
material, let us consider the condition of sedimentation at the west 
during the Carboniferous age. There we have seven thousand 
