J. D. Dana on American Geological History. 317 
ceedingly profuse, was three or four times destroyed and re- 
newed:—not renewed by a re-creation of the same species, but 
by others; and although mostly like the earlier in genera, yet 
each having characteristic marks of the period to which it ag 
longed. And while these Devonian Periods were passing, the 
first land plants appeared, foretellers of the age of verdure, 
next to follow. 
Then come vast beds of conglomerate, a natural opening of a 
: h : 
and coal-beds being formed in Pennsylvania, and fourteen thou- 
feet in Nova Pootis. , 
Thave passed on in rapid review, in order to draw attention 
to the series or succession of changes, instead of details+ So 
brief an outline may lead a mind not familiar with the subject 
to regard the elapsed time as short; whercas to one who follows 
out the various alternations and the whole order of events, the 
dea of time immeasurable becomes almost oppressive. 
paring Te Roger ocean We 
arpa spapiees pa, Drei 1500 to 2000 feet. 
} The names given to the subdivisions of the Paleozoic rocks are the same that 
have been laid down by the New York Geologists, sig assiduous and successful 
terms only in ying them to the jods and epochs : 
formed, so ant be oe thereby the ieterical bearing of geological facts. 
