112 
GEOLOGY CF NORTH CAROLINA. 
The chart presents an example of the absence of certain formations and 
systems and sub-divisions. In the North Carolina series, there is a wide 
gap from the Iluronian, one of the earliest formations, to the Triassic, all 
the intermediate systems, which make up so large a part of the geology 
of the rest of the continent and of the world, being unrepresented ; — the 
Silurian, so grandly developed over the state of New York and the north- 
west, and the great Carboniferous, the most important of the whole, on 
account of its immense stores of mineral fuel. The meaning of this is 
obviously, that during the long period occupied in. the deposition of these 
immense systems, in many parts of the world several miles thick, the sur- 
face of North Carolina was dry land. The Ohio series represents still 
other points ; formations present here are wanting there. And again, 
as seen in the lower part of the chart, systems may exist in localities 
where they do not come to the surface, — outcrop, being overlaid by later 
formations. 
Nor is it necessary to assert that there is absolute synchronism between 
the formations in distant parts of the globe which show the same, or cor- 
responding organic forms ; but only that these different groups of animals 
and plants, the fauna and flora, follow each other in the same order; al- 
though in fact it is probable that in most cases the corresponding groups 
are at least approximately synchronous. 
From this will be apparent the origin and meaning of the terms’a^, 
epoch, horizon , in geology. 
It is evident that only in the sedimentary rocks will fossil remains be 
found. But it is worth while to state that their occurrence is compara- 
tively rare even in these, where they have been subjected to those great 
mechanical convulsions and chemiccal transformations described by the 
term metamorphism, that is, in the older and altered sedimentary rocks. 
It may be for this reason that no fossils have as yet been found in the 
rocks which occupy most of the surface of North Carolina, and are found 
only in the sandstones and shales of our coal formations and the marls 
and other recent deposits near the coast. 
Formations, which are synchronous, i. e. were deposited at the same 
time in different parts of the world, are described as equivalent, or as 
belonging to the same horizon ; and this equivalency is made out mainly 
from the identity, or correspondence of the fossils which they contain ; 
but also partly from stratigraphical considerations of order of succession, 
conformability, &c. 
From a comparison of the series of sedimentary rocks in many parts 
of the world, geologists have reached by gradual approximation a com- 
plete series, which is supposed to represent the successive stages in the 
