shell-shaped fragment or series of fragments; and will
either break it so as to continue the line of one of the existing sides,
or in some other line parallel to that. And yet this resolvedness to
break into shell-shaped fragments running north and south is only
characteristic of the rock at this spot, and at certain other spots
where similar circumstances have brought out this peculiar humor. Forty
yards farther on it will be equally determined to break in another
direction, and nothing will persuade it to the contrary. Forty yards
farther it will change its mind again, and face its beds round to
another quarter of the compass; and yet all these alternating caprices
are each parts of one mighty continuous caprice, which is only masked
for a time, as threads of one color are in a patterned stuff by threads
of another; and thus from a distance, precisely the same cleavage is
seen repeated again and again in different places, forming a systematic
structure; while other groups of cleavages will become visible in their
turn, either as we change our place of observation, or as the sunlight
changes the direction of its fall."

One part of these rocks, I think, no geologist interested in this
subject should pass without examination; viz., the little spur of
Blaitiere drawn in Plate +29+, Fig. 3. It is seen, as there shown, from
the moraine of the Charmoz glacier, its summit bearing S. 40 deg. W.; and
its cleavage bed leaning to the left or S.E., against the aiguille
Blaitiere. If, however, we go down to the extremity of the rocks
themselves, on the right, we shall find that all those thick beams of
rock are actually _sawn into vertical timbers_ by other cleavage,
sometimes so fine as to look almost slaty, directed straight S.E.,
against the aiguille, as if, continued, it would saw it through and
through; finally, cross the spur and go down to the glacier below,
between it and the Aiguille du Plan, and the bottom of the spur will be
found presenting the most splendid mossy surfaces, through which the
true gneissitic cleavage is faintly traceable, dipping _at right angles_
to the beds in Fig. 3, or under the Aiguille Blaitiere, thus concurring
with the beds of La Cote.

I forgot to note that the view of this Aiguille Blaitiere, given in
Plate +39+, was taken from the station marked _q_ in the reference
figure, p. 163; and the sketch of the Aiguille du Plan at p. 187, from
the station marked _r_ in the same figure, a highly int