10 
VOLCANIC AND PRIMARY ROCKS. 
[Ch.II. 
usually contain some peculiar organic remains ; as, for example, 
certain species of shells and corals, or certain plants. 
Volcanic rocks. Besides these strata of aqueous origin, we 
find other rocks which are immediately recognized to be the 
products of fire, from their exact resemblance to those which 
have been produced in modern times by volcanos, and thus 
we immediately establish two distinct orders of mineral masses 
composing the crust of the globe — the sedimentary and the 
volcanic. 
Primary rocks. But if we investigate a large portion of a 
continent which contains within it a lofty mountain range, we 
rarely fail to discover another class, very distinct from either of 
those above alluded to, and which we can neither assimilate to 
deposits such as are now accumulated in lakes or seas, nor to those 
generated by ordinary volcanic action. The class alluded to, 
consists of granite, granitic schist, roofing slate, and many other 
rocks, of a much more compact and crystalline texture than the 
sedimentary and volcanic divisions before mentioned. In the 
unstratified portion of these crystalline rocks, as in the granite 
for example, no organic fossil remains have ever been discovered, 
and only a few faint traces of them in some of the stratified 
masses of the same class; for we should state, that a consider- 
able portion of these rocks are divided, not only into strata, 
but into lamina?, so closely imitating the internal arrangement 
of well-known aqueous deposits, as to leave scarcely any rea- 
sonable doubt that they owe this part of their texture to similar 
causes. 
These remarkable formations have been called primitive, 
from being supposed to constitute the most ancient mineral 
productions known to us, and from a notion that they origi- 
nated before the earth was inhabited by living beings, and 
while yet the planet was in a nascent state. Their high relative 
antiquity is indisputable ; for in the oldest sedimentary strata, 
containing organic remains, we often meet with rounded pebbles 
of the older crystalline rocks, which must therefore have been 
consolidated before the derivative strata were formed out of 
