In consequence of the curious chemical change which has thus taken place in the animal juices of the _Asterolepis_, its remains often occur in a state of beautiful preservation: the pervading bitumen, greatly more conservative in its effects than the oils and gums of an old Egyptian undertaker, has maintained, in their original integrity, every scale, plate, and bone. They may have been much broken ere they were first committed to the keeping of the rock, or in disentangling them from its rigid embrace; but they have, we find, caught no harm when under its care. Ere the skeleton of the Bruce, disinterred after the lapse of five centuries, was recommitted to the tomb, such measures were taken to secure its preservation, that, were it to be again disinterred, even after as many more centuries 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 the pores, and fill up the central hollows, and which, soon hardening around them, formed a bituminous matrix, in which they may lie unchanged for a thousand years. Now, exactly such was the process to which nature resorted with these gigantic skeletons of the Old Red Sandstone. 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 flame like torches. Though black as jet, they still retain, too, in a considerable degree, the peculiar _qualities_ of the original substance. The late Mr. George Sanderson of Edinburgh, one of the most ingenious lapidaries in the kingdom, and a thoroughly intelligent man, made several preparations for me, for microscopic examination, from the teeth and bones; and though they were by far the oldest vertebrate remains he had ever seen, they exhibited, he informed me, in the working, more of the characteristics of recent teeth and bone than any other fossils he had ever operated upon. Recent bone when in the course of being reduced on the wheel to the degree of thinness necessary to secure transparency, is apt, under the heat induced by the friction, to acquire a springy elasticity, and to start up from the glass slip to which it has been cemented; whereas bone in the fossil state usually lies as passive, in such circumstances, as the stone which envelopes it. Mr. Sanderson was, however, surprised to find that the bone of the _Asterolepis_ still retained its elasticity, and was scarce less liable, when heated, to start from the glass,—a peculiarity through which he at first lost several preparations. I have seen a human bone that had for ages been partially embedded in a mass of adipocere, partially enveloped in the common mould of a churchyard, exhibit two very different styles of keeping. In the adipocere it was as fresh and green as if it had been divested of the integuments only a few weeks previous; whereas the