.14
ê
of many of the strata called secondary.
Nor does it seem improbable, that granite
may again be formed, by the fusion and
crystallization of secondary strata, at sOme
future revolution of the globe ; for our coal
strata, with the shale and silicious sandstone,
contain together the elements of
granite, gneiss, mica slate, and clay slate.
The latter, Daubuison found identical in
its composition with coal shale, except that
it contained less carbon.* Were the secondary
strata to remain by any cause in
a state of perfect fusion, for a sufficient
length of time to admit the formation of
new compounds, by elective attraction and
crystalline polarity, nothing further would
seem required for the formation of all the
mineral substances of which primary rocks
are composed. Whatever objections may
rest against this theory, it does not present
such opposition to the known laws of nature,
as that which supposes granite rocks
to have been deposited by aqueous precipi*
Coal shale. Silex
Alumine
Potass
Magnesia
48
23
4.7
1.6
together with iron manganese and carbon.
tations. We know that crystals of felspar
are formed in lavas, but we know nothing
analagous to the formation of a crystal of
felspar by water. Independently of all theoretical
systems, the relative position of the
granite ofthe Alps, is an important geological
fact, to which I shall have occasion to
refer more particularly in some of the following
chapters.
kÎ . &
ft. I