his state of keeping seems to be wholly owing to the curious
chemical change that has taken place in their substance. Ere the
skeleton of the Bruce, disinterred entire after the lapse of five
centuries, was recommitted to the tomb, there were such measures taken
to secure its preservation, that were it to be again disinterred even
after as many centuries more had passed, it might be found retaining
unbroken its gigantic proportions. There was molten pitch poured over
the bones in a state of sufficient fluidity to permeate all their
pores, and fill up the central hollows, and which, soon hardening around
them, formed a bituminous matrix, in which they may lie unchanged for
more than a thousand years. Now, exactly such was the process of keeping
to which nature resorted with these skeletons of the Old Red Sandstone.
The animal matter with which they were charged had been converted into a
hard black bitumen. Like the bones of the Bruce, they are bones steeped
in pitch; and so thoroughly is every pore and hollow still occupied,
that, when cast into the fire, they flamed like torches. In one of the
beds at which we have now arrived Mr. Dick found the occipital plates of
a Holoptychius of gigantic proportions. The frontal plates measured full
sixteen inches across, and from the nape of the neck to a little above
the place of the eyes, full eighteen; while a single plate belonging to
the lower part of the head measures thirteen and a half inches by seven
and a half. I have remarked, in my little work on the Old Red
Sandstone,--founding on a large amount of negative evidence, that a
mediocrity of size and bulk seems to have obtained among the fish of the
Lower Old Red, though in at least the Upper formation, a considerable
increase in both took place. A single piece of positive evidence,
however, outweighs whole volumes of a merely negative kind. From the
entire plate now in my possession, which is identical with one figured
in Mr. Noble of St. Madoes' specimen, and from the huge fragments of the
upper plates now before me, some of which are full five-eighth parts of
an inch in thickness, I am prepared to demonstrate that this
Holoptychius of the Lower Old Red must have been at least thrice the
size of the _Holoptychius Nobilissimus_ of Clashbennie.

Still we pass on, though with no difficulty, over the rough contorted
crags, worn by the surf into deep ruts and uneven ridges, gnarled
protuberances, and crater-like hollows. The f