114 
GEOLOGY OF NORTH CAROLINA. 
slates, chlorites, quartzytes and diorytes ; with cherty, jaspery and epi- 
dotic beds, and much specular iron ore. 
Like the*'preceding, this formation is destitute of fossils, and so its 
horizon cannot be determined with the same degree of certainty as those 
of later periods. And 'hence these two series, with the first, are grouped 
into one age, under the name Azoic, which means without life, or sim- 
ply (Dr. Dana) Archcean, {ancient). The term Azoic is open to the ob- 
jection that these rocks are not now, as formerly, supposed to have been 
deposited before the introduction of organic life ; the beds of graphite 
and graphitic gneisses and slates are commonly referred to a vegetable 
origin ; and the limestones and iron ores are supposed to have been accu- 
mulated through organic agency, as now. But all traces of their origin 
have been obliterated. 
Within a few years this term has given place to Eozoic, ( life-dawn ), 
from the discovery of a supposed organism of low order, but its organic 
character is still in doubt. 
These rocks occupy a considerable extent of surface in this State. 
SILURIAN SYSTEM. 
The azoic (or archaean) rocks are succeeded by those of the Silurian 
system. It includes stratified rocks of every description, sandstones, clay- 
slates, shales, conglomerates, limestones ; and abounds in marine fossils ; 
among which, the various kinds of shell fish (mollusca) predominate and 
hence the period is characterized as the Molluscan Age. 
The organic forms of this age are all of a low order, and only in the 
upper terms of the series have remains of land plants or vertebrate 
animals been found. 
The rocks of this series have a very wide distribution. They occupy 
the larger part of the surface of the State of New York, where they were 
first and most minutely studied in this country, and from which most of 
the sub-divisions were established and named, and their characteristic 
fossils ascertained. It is found in some of its sub-divisions, throughout 
the northwestern states, and in the Alleghaniesof Pennsylvania and Vir- 
ginia, in Kentucky, Tennessee, Alabama, Texas and Missouri, and in the 
Pocky Mountains; and it is also largely developed in the old world. 
In some localities, and especially in its lower formations, the rocks 
have been. changed into crystalline schists, gneisses and even granites, 
and their fossils obliterated. The best examples of this metamorphism 
are found in New England. 
This formation, so far as known is not represented in this State, except 
