obe.
These two species are, _first_, granite regular in its composition, or
stratified in its construction; and, _secondly_, granite in mass, or
irregular in its construction. Let us now endeavour to make use of these
generalizations and distinctions.

In examining the great diversity of our whinstone, trap, or basaltes, it
is found at last to granulate into granite; at the same time those two
different species of rock-stone may be distinguished. A perfect granite
has not in its composition necessarily any argillaceous earth, farther
than may be in the natural constitution of its distinct parts; whereas,
a perfect basalt may have abundance of this substance, without any
quartz or any siliceous body. A perfect granite, is, therefore, an
extremely hard stone, having quartz and feldspar for its basis; but a
perfect whin or basaltes may be extremely soft, so as to cut easily with
a knife. In like manner granite is a composition which graduates into
porphyry; but porphyry is only whinstone of a harder species. Therefore,
though perfectly distinct, those three things graduate into each other,
and may be considered as the same.

Granite and whinstone, or basaltes, though distinct compositions, thus
graduating into each other; and whinstone, as well as porphyry, being
without doubt a species of lava, we may consider the granite which is
found in mass without stratification, in like manner as we do the masses
of whinstone, basaltes, or Swedish trap, as having flowed in the bowels
of the earth, and thus been produced by the chance of place, without any
proper form of its own, or in an irregular shape and construction. In
this manner would be explained the irregular shape or structure of those
granite masses; and thus great light would be thrown upon the waved
structure of the stratified alpine stone, which, though it has not been
made to flow, has been brought to a great degree of softness, so as to
have the original straight lines of its stratification changed to
those undulated or waving lines which are in some cases extremely much
incurvated.

It remains only to confirm this reasoning, upon our principles, by
bringing actual observation to its support; and this we shall do from
two of the best authorities. The Chevalier de Dolomieu, in describing
the volcanic productions of Etna, mentions a lava which had flowed from
that mountain, and which may be considered as a granite. But M. de
Saussure has put this matter out of doubt