sts give them the appearance of solid massive
rocks; nor is this altogether wrong, especially when the natural joints
of the shale appear prominent after particular accidents; they should,
however, never be made to resemble [i.e. in solidity] limestone or
gritstone."

Now the Yoredale shales are members of the group of rocks which I have
called slaty coherents, and correspond very closely to those portions of
the Alpine slates described in Chap. X. Sec. 4; their main character is
continual separation into fine flakes, more or less of Dante's
"iron-colored grain;" which, however, on a large scale, form those
somewhat solid-looking masses to which Mr. Phillips alludes in his
letter, and which he describes, in his recently published Geology, in
the following general terms: "The shales of this tract are usually dark,
close, and fissile, and traversed by extremely long straight joints,
dividing the rock into rhomboidal prisms" (i.e. prisms of the shape
_c_, Fig. 83, in the section).

Sec. 34. Turner had, therefore, these four things to show:--1. Flaky
division horizontally; 2. Division by rhomboidal joints; 3. Massy
appearance occasionally, somewhat concealing the structure; 4. Local
contortion of the beds. (See passage quoted of Mr. Phillips's letter).

[Illustration: FIG. 84.]

Examine, then, the plate just given (12 A). The cleavage of the shales
runs diagonally up from left to right; note especially how delicately it
runs up through the foreground rock, and is insisted upon, just at the
brow of it, in the angular step-like fragments; compare also the etching
in the first volume. Then note the upright pillars in the distance,
marked especially as rhomboidal by being drawn with the cleavage still
sloping up on the returning side, as at _a_, Fig. 83, not as at _b_,
which would be their aspect if they were square; and then the indication
of interruption in the structure at the brow of the main cliff, where,
as well as on the nearer mass, exposure to the weather has rounded away
the cleavages.

This projection, as before mentioned, does exist at the spot; and I
believe is partly an indication of the contortion in the beds alluded to
by Mr. Phillips; but no one but Turner would have fastened on it, as in
anywise deserving special attention.

For the rest, no words are of any use to explain the subtle fidelity
with which the minor roundings and cleavages have been expressed by him.
Fidelity of this kind can only be estim