The animal remains, though less numerous, are more interesting. They are identical with those of the Den of Balruddery. I saw, in the possession of the superintendent of the quarries, a well-preserved head of the Cephalaspis Lyellii. The crescent-shaped horns were wanting, and the outline a little obscure; but the eyes were better marked than in almost any other specimen I have yet seen, and the circular star-like tubercles which roughen the large occipital buckler, to which the creature owes its name, were tolerably well defined. I was shown the head of another individual of the same species in the centre of a large slab, and nothing could be more entire than the outline. The osseous plate still retained the original brownish-white hue of the bone, and its radiated porous texture; and the sharp crescent-shaped horns were as sharply defined as during the lifetime of the strangely organized creature which they had defended. In both specimens the thin angular body was wanting. Like almost all the other fish of the Old Red Sandstone, the bony skeleton of the Cephalaspis was external—as much so as the shell of the crab or lobster: it presented at all points an armor of bone, as complete as if it had been carved by the ivory-turner out of a solid block; while the internal skeleton, which in every instance has disappeared, seems to have been composed of cartilage. I have compared its general appearance to a saddler's cutting-knife;—I should, perhaps, have said a saddler's cutting-knife divested of the wooden handle—the broad, bony head representing the blade, and the thin angular body the iron stem usually fixed in the wood. No existence of the present creation at all resembles the Cephalaspis. Were we introduced to the living creatures which now inhabit the oceans and rivers of Mars and Venus, we could find nothing among them more strange in appearance, or more unlike our living acquaintances of the friths and streams, than the Cephalaspides of Carmylie.
I observed, besides, in the quarry, remains of the huge crustacean of Balruddery. The plates of the Cephalaspis retain the color of the original bone; the plates of the crustacean, on the contrary, are of a deep red tint, which contrasts strongly with the cold gray of the stone. They remind one, both in shape and hue, of pieces of ancient iron armor, fretted into semi-elliptical scales, and red with rust. I saw with one of the workmen what seemed to have been the continuous tail-flap of an individual of very considerable size. It seemed curiously puckered where it had joined to the body, much in the manner that a gown or Highlander's kilt is puckered where it joins to the waistband; and the outline of the whole plate was marked by what I may venture to term architectural elegance. The mathematician could have described it with his ruler and compasses. The superintendent pointed out to me another plate in a slab dressed for a piece of common pavement. It was a regularly formed parallelogram, and had obviously composed one of the jointed plates which had covered the creature's body. I could not so easily assign its place to yet a third plate in the possession of the Rev. Mr. Wilson, of Carmylie. It is colored, like the others, and like them, too, fretted into minute scales, but the form is exactly that of a heart—not such a heart as the anatomist would draw, but such a heart, rather, as we see at times on valentines of the humbler order, or on the ace of hearts in a pack of cards. Possibly enough it may have been the breastplate of this antique crustacean of the Cornstones. The spawn of our common blue lobster is composed of spherical black grains, of nearly the size of mustard-seed. It struck me as not very improbable that the reticulated markings of the flagstones of Carmylie may have been produced by the minute eggs of this fossil crustacean, covered up by some hastily deposited layer of mingled mud and sand, and forced into the polygonal form by pressing against each other, and by the weight from above.
The gray fissile bed in which these organisms occur was perforated to its base on two several occasions, and in different parts of the quarries—in one instance, merely to ascertain its depth; in the other, in the course of excavating a tunnel. In the one case it was found to rest on a bed of trap, which seemed to have insinuated itself among the strata with as little disturbance, and which lay nearly as conformably to them as the greenstone bed of Salisbury Crags does to the alternating sandstones and clays which both underlie and overtop it. In the other instance the excavators arrived at a red, aluminous sandstone, veined by a purplish-colored oxide of iron. The upper strata of the quarry are overlaid by a thick bed of grayish-red conglomerate.
Leaving behind us the quarries of Carmylie, we descend the hill-side, and rise in the system as we lower our level and advance upon the sea. For a very considerable distance we find the rock covered up by a deep-red diluvial clay, largely charged with water-worn boulders, chiefly of the older primary rocks, and of the sandstone underneath. The soil on the higher grounds is moory and barren—a consequence, in great part, of a hard, ferruginous pan, which interposes like a paved floor between the diluvium and the upper mould, and which prevents the roots of the vegetation from striking downwards into the tenacious subsoil. From its impervious character, too, it has the effect of rendering the surface a bog for one half the year, and an arid, sun-baked waste for the other. It seems not improbable that the heaths which must have grown and decayed on these heights for many ages, may have been main agents in the formation of this pavement of barrenness. Of all plants, they are said to contain most iron. According to Fourcroy, a full twelfth part of the weight of oak, when dried, is owing to the presence of this almost universally diffused metal; and the proportion in our common heaths is still larger. It seems easy to conceive how that, as generation after generation withered on these heights, and were slowly resolved into a little mossy dust, the minute metallic particles which they had contained would be carried downwards by the rains through the lighter stratum of soil, till, reaching the impermeable platform of tenacious clay beneath, they would gradually accumulate there, and at length bind its upper layer, as is the nature of ferruginous oxide, into a continuous stony crust. Bog iron, and the clay ironstone, so abundant in the Coal Measures, and so extensively employed in our iron-works, seem to have owed their accumulation in layers and nodules to a somewhat similar process, through the agency of vegetation. But I digress.
The rock appears in the course of the Elliot, a few hundred yards above the pastoral village of Arbirlot. We find it uptilted on a mass of claystone amygdaloid, that has here raised its broad back to the surface amid the middle shales and sandstones of the system. The stream runs over the intruded mass; and where the latter terminates, and the sandstones lean against it, the waters leap from the harder to the softer rock, immediately beside the quiet parish burying-ground, in a cascade of some eight or ten feet. From this point, for a full mile downwards, we find an almost continuous section of the sandstone—stratum leaning against stratum—in an angle of about thirty. The portion of the system thus exhibited must amount to many hundred yards in vertical extent; but as I could discover no data by which to determine regarding the space which may intervene between its lowest stratum and the still lower beds of Carmylie, I could form no guess respecting the thickness of the whole. In a bed of shale, about a quarter of a mile below the village, I detected several of the vegetable impressions of Carmylie, especially those of the grass-weed looking class, and an imperfectly preserved organism resembling the parallelogramical scale of a Cephalaspis. The same plants and animals seem to have existed on this high platform as on the Carmylie platform far beneath.
A little farther down the course of the stream, and in the immediate neighborhood of the old weather-worn tower of the Ouchterlonies, there occurs what seems a break in the strata. The newer sandstones seem to rest unconformably on the older sandstones which they overlie. The evening on which I explored the course of the Elliot was drizzly and unpleasant, and the stream swollen by a day of continuous rain, and so I could not examine so minutely as in other circumstances I would have done, or as was necessary to establish the fact. In since turning over the Elements of Lyell, however, I find, in his section of Forfarshire, that a newer deposit of nearly horizontal strata of sandstone and conglomerate lies unconformably, in the neighborhood of the sea, on the older sandstones of the district; and the appearances observed near the old tower mark, it is probable, one of the points of junction—a point of junction also, if I may be so bold as venture the suggestion, of the formation of the Holoptychius nobilissimus with the formation of the Cephalaspis—of the quartzose conglomerate with the Cornstones. In my hurried survey, however, I could find none of the scales or plates of the newer ichthyolite in this upper deposit, though the numerous spherical markings of white, with their centrical points of darker color, show that at one time the organisms of these upper beds must have been very abundant.
We pass to the upper formation of the system. Over the belt of mingled gray and red there occurs in the pyramid a second deep belt of red conglomerate and variegated sandstone, with a band of lime a-top, and over the band a thick belt of yellow sandstone, with which the system terminates.[AN] Thus the second pyramid consists mineralogically, like the first, of three great divisions, or bands; its two upper belts belonging, like the three belts of the other, to but one formation—the formation known in England as the Quartzose Conglomerate. It is largely developed in Scotland. We find it spread over extensive areas in Moray, Fife, Roxburgh, and Berwick shires. In England, it is comparatively barren in fossils; the only animal organic remains yet detected in it being a single scale of the Holoptychius found by Mr. Murchison; and though it contains vegetable organisms in more abundance, so imperfectly are they preserved, that little else can be ascertained regarding them than that they were land plants, but not identical with the plants of the Coal Measures. In Scotland, the formation is richly fossiliferous, and the remains belong chiefly to the animal kingdom. It is richly fossiliferous, too, in Russia, where it was discovered by Mr. Murchison, during the summer of last year, spread over areas many thousand square miles in extent. And there, as in Scotland, the Holoptychius seems its most characteristic fossil.
[AN] There still exists some uncertainty regarding the order in which the upper beds occur. Mr. Duff, of Elgin, places the limestone band above the yellow sandstone; Messrs. Sedgwick and Murchison assign it an intermediate position between the red and yellow. The respective places of the gray and red sandstones are also disputed, and by very high authorities; Dr. Fleming holding that the gray sandstones overlie the red, (see Cheek's Edinburgh Journal for February, 1831,) and Mr. Lyell, that the red sandstones overlie the gray, (see Elements of Geology, first edit., pp. 99-100.) The order adopted above consorts best with the results of the writer's observations, which have, however, been restricted chiefly to the north country. He assigns to the limestone band the middle place assigned to it by Messrs. Sedgwick and Murchison, and to the gray sandstone the inferior position assigned to it by Mr. Lyell; aware, however, that the latter deposit has not only a coping, but also a basement, of red sandstone—the basement forming the upper member of the lower formation.
The fact seems especially worthy of remark. The organisms of some of the newer formations differ entirely, in widely separated localities, from their contemporary organisms, just as, in the existing state of things, the plants and animals of Great Britain differ from the plants and animals of Lapland or of Sierra Leone. A geologist who has acquainted himself with the belemnites, baculites, turrilites, and sea-urchins of the Cretaceous group in England and the north of France, would discover that he had got into an entirely new field among the hippurites, sphærulites, and nummulites of the same formations, in Greece, Italy, and Spain; nor, in passing the tertiary deposits, would he find less striking dissimilarities between the gigantic, mail-clad megatherium and huge mastodon of the Ohio and the La Plate, and the monsters, their contemporaries, the hairy mammoth of Siberia, and the hippopotamus and rhinoceros of England and the Continent. In the more ancient geological periods, ere the seasons began, the case is essentially different; the contemporary formations, when widely separated, are often very unlike in mineralogical character, but in their fossil contents they are almost always identical. In these earlier ages, the atmospheric temperature seems to have depended more on the internal heat of the earth, only partially cooled down from its original state, than on the earth's configuration or the influence of the sun. Hence a widely spread equality of climate—a greenhouse equalization of heat, if I may so speak; and hence, too, it would seem, a widely spread Fauna and Flora. The greenhouses of Scotland and Sweden produce the same plants with the greenhouses of Spain and Italy; and when the world was one vast greenhouse, heated from below, the same families of plants, and the same tribes of animals, seem to have ranged over spaces immensely more extended than those geographical circles in which, in the present time, the same plants are found indigenous, and the same animals native. The fossil remains of the true Coal Measures are the same to the westward of the Alleghany Mountains as in New Holland, India, Southern Africa, the neighborhood of Newcastle, and the vicinity of Edinburgh. And I entertain little doubt that, on a similar principle, the still more ancient organisms of the Old Red Sandstone will be found to bear the same character all over the world.