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talline matter, and contain no fragments of other 
rocks. 
The secondary rocks, or strata, consist only 
partly of crystalline matter, contain fragments of 
other rocks or strata ; often abound in the remains 
of vegetables and marine animals ; and sometimes 
contain the remains of land animals. 
The primary rocks are generally arranged in 
large masses, or in layers vertical, or more or less 
inclined to the horizon. 
The secondary rocks are usually disposed in 
strata or layers, parallel, or nearly parallel, to the 
horizon. 
The number of primary rocks which are com- 
monly observed in nature are eight. 
First, granite , which, as has been mentioned, is 
composed of quartz, feldspar, and mica ; when these 
bodies are arranged in regular layers in the rock, it 
is called gneis . 
Second, micaceous schistus , which is composed of 
quartz and mica arranged in layers, which are 
usually curvilineal. 
Third, sienite , which consists of the substance 
called hornblende and feldspar. 
Fourth, serpentine , which is constituted by feld- 
spar and a body named resplendent hornblende ; 
and their separate crystals are often so small as to 
give the stone a uniform appearance : this rock 
abounds in veins of a substance called steatite , or 
soap rock . 
Fifth, porphyry , which consists of crystals of 
feldspar, embedded in the same material, but 
usually of a different colour. 
N 
