oftener obliquely crossing it, and sometimes, apparently, altogether
independent of it, maintaining a consistent and unvarying slope through
a series of beds contorted and undulating in every conceivable
direction. These lines of lamination extend their influence to the
smallest fragment, causing it (as, for example, common roofing slate) to
break smooth in one direction, and with a ragged edge in another, and
marking the faces of the beds and joints with distinct and numberless
lines, commonly far more conspicuous in a near view than the larger and
more important divisions.

Sec. 4. Variety and seeming uncertainty under which these laws are
manifested.

Now, it cannot be too carefully held in mind, in examining the
principles of mountain structure, that nearly all the laws of nature
with respect to external form are rather universal tendencies, evidenced
by a plurality of instances, than imperative necessities complied with
by all. For instance, it may be said to be a universal law with respect
to the boughs of all trees that they incline their extremities more to
the ground in proportion as they are lower on the trunk, and that the
higher their point of insertion is, the more they share in the upward
tendency of the trunk itself. But yet there is not a single group of
boughs in any one tree which does not show exceptions to the rule, and
present boughs lower in insertion, and yet steeper in inclination, than
their neighbors. Nor is this defect or deformity, but the result of the
constant habit of nature to carry variety into her very principles, and
make the symmetry and beauty of her laws the more felt by the grace and
accidentalism with which they are carried out. No one familiar with
foliage could doubt for an instant of the necessity of giving evidence
of this downward tendency in the boughs; but it would be nearly as great
an offence against truth to make the law hold good with every individual
branch, as not to exhibit its influence on the majority. Now, though the
laws of mountain form are more rigid and constant than those of
vegetation, they are subject to the same species of exception in
carrying out. Though every mountain has these great tendencies in its
lines, not one in a thousand of those lines is absolutely consistent
with and obedient to this universal tendency. There are lines in every
direction, and of almost every kind, but the sum and aggregate of those
lines will invariably indicate the