24 OP GRANITE. 
5. ^Alluvial Rocks and Soil. — After the waters of the deluge 
had retired, the rocky strata that had been left bare, were reduced 
in some cases to a coarse gravel or to powder, and the finer par- 
ticles washed down and deposited, intermixed with vegetable and 
animal matter, in the vallies, either upon land or in the bed of the 
sea. Rocks of volcanic origin, were regarded by Werner, as 
occupying too small a space on the surface of the earth, to merit 
particular notice. 
Such is Werner's theory. As he was an excellent mineralo- 
gist, and an earnest and intelligent observer, it may be expected 
that whatever be the fate of his theory, the distinctions established 
by him amongst the rocks, will commend themselves to the judg- 
ment of the Geologists of succeeding times. One of his errors, 
was that of allowing too little space and importance to the forma- 
tions of volcanic origin, and refusing to include basalt amongst 
them. In the place of his class of alluvial, that of tertiary forma- 
tions has been substituted, leaving the whole number still the 
same. 1. Primitive, 2. Transition, 3. Secondary, 4. Tertiary, 
5. Overlying or Volcanic. 
OF GRANITE. 
15. Our attention will be first directed to the primitive rocks, 
and first of all to that, which according to Werner, was first 
separated by crystallization from the original, semifluid, chaotic 
mass; which is the central nucleus that underlies all the other 
strata, which also pierces through them, and exhibits its rugged 
and barren head, on the summits of some of the loftiest mountains. 
This is granite. The other primitive rocks, gneiss, mica slate, 
quartz rock, clay slate, limestone, and serpentine, will follow. 
A few that resemble mica slate in their structure, but differ from 
it in their composition, will be most conveniently treated of un- 
der that title. These are the chlorite, talcose, hornblende, and 
actinolite schists. 
Proper granite is a granular aggregate of the simple minerals, 
quartz, feldspar, and mica; the feldspar being generally the most 
abundant of the three, crystalline in its structure and unstratified. 
It has evidently been produced by an irregular and imperfect 
crystallization. It presents itself at the surface of the earth, in 
large masses, the sharp angles of which having been obliterated 
by the action of the elements, they often make some distant ap- 
proaches to a spherical form. The name it bears, appears to have 
been applied without much precision to certain stones employed 
in architecture and statuary, with reference to their granular 
structure, before the time of Werner, and to have had its meaning 
first fixed and limited by him to a particular rock. Besides the 
proper granite just described, there is a considerable number 
of rocks, like it of a crystalline and granular structure and un- 
stratified, but differing from it in their mineral constitution ; 
some containing hornblende, chlorite, or talc, instead of micaj 
