he Coccosteus and Pterichthys,
but to the far later ages of the Plesiosaurus and the fossil crocodile.
I found them associated with more reptilian remains, of a character more
unequivocal than have been yet exhibited by any other deposit in
Scotland.

What first strikes the eye, in approaching the _Ru-Stoir_ from the west,
is the columnar character of the stone. The precipices rise immediately
over the sea, in rude colonnades of from thirty to fifty feet in height;
single pillars, that have fallen from their places in the line, and
exhibit a tenacity rare among the trap-rocks,--for they occur in
unbroken lengths of from ten to twelve feet,--lie scattered below; and
in several places where the waves have joined issue with the precipices
in the line on which the base of the columns rest, and swept away the
supporting foundation, the colonnades open into roomy caverns, that
resound to the dash of the sea. Wherever the spray lashes, the pale red
hue of the stone prevails, and the angles of the polygonal shafts are
rounded; while higher up all is sharp-edged, and the unweathered surface
is covered by a gray coat of lichens. The tenacity of the prostrate
columns first drew my attention. The builder scant of materials would
have experienced no difficulty in finding among them sufficient lintels
for apertures from eight to twelve feet in width. I was next struck with
the peculiar composition of the stone; it much rather resembles an
altered sandstone, in at least the weathered specimens, than a trap, and
yet there seemed nothing to indicate that it was an _Old Red_ Sandstone.
Its columnar structure bore evidence to the action of great heat; and
its pale red color was exactly that which the Oolitic sandstones of the
island, with their slight ochreous tinge, would assume in a common fire.
And so I set myself to look for fossils. In the columnar stone itself I
expected none, as none occur in vast beds of the unaltered sandstones,
out of some one of which I supposed it might possibly have been formed;
and none I found: but in a rolled block of altered shale of a much
deeper red than the general mass, and much more resembling Old Red
Sandstone, I succeeded in detecting several shells, identical with those
of the deposit of blue clay described in a former chapter. There
occurred in it the small univalve resembling a Trochus, together with
the oblong bivalve, somewhat like a Tellina; and, spread thickly
throughout the block, lay fragm