normous masses of other rocks, more or less resembling it
in character, of which the following are universal characteristics.

Characteristics of Slaty Coherents.

1. Softness of texture.

2. Lamination of structure.

Sec. 2. First. They nearly always, as just said, contain more of the earth,
which is the basis of clay, than the crystalline rocks; and they can be
scratched or crushed with much greater facility. The point of a knife
will trace a continuous powdery streak upon most of the coherent rocks;
while it will be quite powerless against a large portion of the granular
knots in the crystallines. Besides this actual softness of substance,
the slaty coherents are capable of very fine division into flakes, not
irregularly and contortedly, like the crystallines, but straightly, so
as to leave a silky lustre on the sides of the fragments, as in roofing
slate; and separating with great ease, yielding to a slight pressure
against the edge. Consequently, although the slaty coherents are capable
of forming large and bold mountains, they are liable to all kinds of
destruction and decay in a far greater degree than the crystallines;
giving way in large masses under frost, and crumbling into heaps of
flaky rubbish, which in its turn dissolves or is ground down into
impalpable dust or mud, and carried to great distances by the mountain
streams. These characters render the slaty coherents peculiarly adapted
for the support of vegetation; and as, though apparently homogeneous,
they usually contain as many chemical elements as the crystallines, they
constitute (as far as regards the immediate nourishment of soils) the
most important part of mountain ranges.

3. Darkness and blueness in color.

Sec. 3. I have already often had occasion to allude to the apparent
connexion of brilliancy of color with vigor of life, or purity of
substance. This is preeminently the case in the mineral kingdom. The
perfection with which the particles of any substance unite in
crystallization corresponds, in that kingdom, to the vital power in
organic nature; and it is a universal law, that according to the purity
of any substance, and according to the energy of its crystallization, is
its beauty or brightness. Pure earths are without exception white when
in powder; and the same earths which are the constituents of clay and
sand, form, when crystallized, the emerald, ruby, sapphire, amethyst,
and opal. Darkness and dulness of color are