and argillaceous earths, as granite, slate, &c.--Transition
rocks, supposed to have been formed during the transition of the earth
into a habitable state; they differ from the primitive, in containing
the remains of marine animals:--the Secondary rocks, containing the
remains of animals and vegetables, and consequently formed after their
creation;--the Tertiary formation, composed of layers of clay, sand,
gravel, and marl, and containing peculiar organic remains;--and the
Alluvial formation, constituted of parts of previous rocks separated
by water, &c., and deposited in beds.

_Petrifaction_, an animal or vegetable substance turned to
stone.

_Silicious_, consisting of flint.

_Transition_, change from one state to another.

_Argillaceous_, clayey, consisting of clay.

_Chaotic_, resembling chaos, confused.

_Chaos_, confusion, a mingled heap; a term used in speaking
of the world while yet without form; a Greek word,
signifying a confused mass.

_Alluvial_, deposited from water.

Of what is this last compounded?

The Alluvial formation is composed of sand, gravel, loam, clay, turf,
&c., and contains plants, roots, moss, bones, petrified wood, and
skeletons of animals. It is distinguished from the Tertiary formation
chiefly by its superior position, and by extending over regions where
existing streams or other causes now in action could have produced it.
Some geologists mention another formation called the Volcanic, because
composed of minerals thrown from the crater of a volcano, such as
pumice stones, lava, &c.

_Crater_, the mouth or opening of a volcano.

_Petrified_, hardened into stone.

You mentioned Silicious and Argillaceous Earths: is not, then, the
earthy covering of our globe of one common character?

No; by earth is understood a combination of many distinct bodies.
Chemists, by separating earths from each other, and from foreign
matters connected with them, have discovered nine or ten primitive
earths; all of these, except silex, are compounds of oxygen with
metallic bases.

_Chemist_, one who understands the science of chemistry.

Of which of these Simple or Primitive Earths are the solid portions of
the globe principally composed?

Of flint or silex, lime or calcareous earth, and clay or argil, in
various degrees of combination, the greatest parts of the mountains
and plains, and the whole of what we commonly under