numerous and discordant assemblage of specimens into distinct groups, the specific identity of which, when thus collected, is at once verified by the eye.

But the reader, unless very thoroughly a geological one, must be of opinion that I have said quite enough about the Belemnite. I may, however, venture to add further, that its place in the geological scale is not without its interest. The periods of the more ancient formations, from the older Silurian to the older New Red Sandstone inclusive, had all passed away ere the order was called into existence. It then sprung into being nearly contemporaneously with the bird and the reptile; and, after existing by myriads during the Oolitic and Cretaceous periods, passed into extinction when the ocean of the Chalk had ceased to exist, and just as quadrupeds of the higher order were on the eve of appearing on the stage, but had not yet appeared. Since the period in which it lived, though geologically modern, the surface of the earth must have witnessed many strange revolutions. There have been Belemnites dug out of the sides of the Himalaya mountains, seventeen thousand feet above the level of the sea.

COPROLITES OF THE LIAS.

Large coprolites of peculiar appearance, some of them charged with fish-scales of the ganoid order, are tolerably abundant; and they belonged, I have little doubt, to saurians. When bringing home with me, many years since, a well-marked specimen, I overtook by the way an acquaintance who had passed a considerable part of his life in Dutch Guiana. The thought did not at first occur to me of submitting to him my specimen. As we walked on together, he thrust his hand into his pocket to bring out his

handkerchief, and brought out, instead, a large mass of damaged snuff. "Ah," he exclaimed, "that roguish boy! I was standing with my neighbor, the shopkeeper, this morning, when he was opening up a cask of snuff that had got spoiled with sea-water; and his boy, seeing my pocket provokingly open I suppose, must have dropped in this huge lump! The joke seems a small one," he continued, "but it must be at least rather a natural one. The only other trick of the kind ever played me was by a South American Indian, on the banks of the Demerara: he dropped, unseen, into the pocket of my light nankeen jacket a piece of sun-baked alligator's dung." "What sort of a looking substance was it?" I asked, uncovering my specimen, and submitting it to his examination; "wast it at all like that?" "Not at all unlike," was the reply; "it bore an exactly similar pale yellow tint, as if, like the dung of our sea-birds that swallow and digest fish-bones, it contained abundance of lime; and it was sprinkled over, in the same way, with the glittering enamelled scales of that curious fish the bony pike, so common, as you are aware, in our South American rivers."

INTRUSIVE DIKES OF EATHIE.

There are appearances in connection with the Lias of Eathie which seem well suited to puzzle the geologist, and which have, in fact, already puzzled geologists not a little. We find them traversed by intrusive dykes of what seems a grayish-colored trap, extremely obstinate in yielding to the hammer, and which stand up among the softer shales like the walls of some ruined village. They are trap-dikes in every essential except one; - they occur in every possible angle of disagreement with the line of the, strata: in

some places they inclose the shale in slim, insulated strips, as a river incloses its islands; in others they traverse it with minute veins connected with the larger masses, in the way in which granite is so often seen traversing gneiss; in yet others the limestone in contact with them seems positively altered; the blue nodule has, at the line of junction, its strip of crystalline white, and the shale assumes an indurated and veinous character; the dikes are, in short, trap dikes in every essential except one; but the wanting essential is of importance enough to constitute the problem in the case; they are not composed of trap. Some of our mineralogists have been a good deal puzzled by finding crystals of sandstone as regular in their planes and angles as if formed of any of the earths, or salts, or metals, whose law it is to build themselves up into little erections correctly mathematical in every point and line; and they have read the mystery by supposing that these sandstone crystals are mere casts moulded in the cavities in which crystals had once existed. The puzzle of the Lias dikes is of an exactly similar kind: they are composed, not of an igneous rock, but of a hard, calcareous sandstone, undistinguishable in hand-specimens from an indurated sandstone of the Lower Oolite, which may be found on the shore beneath Dunrobin, alternating with shale-beds of the period of the Oxford clay. I succeeded in finding in it, on one occasion, a shell in the same state of keeping in which shells are so often found in the resembling rocks of Sutherland, but the species unluckily could not be distinguished. A common microscope at once detects the mechanical character of the mass; and I have learned that Dr. Fleming, after reducing a portion of it, sent him as an igneous rock, to its original sand, simply by

submerging it in acid, expressed some little fear lest the sender should not have been quite "up to trap."

The explanation of the phenomenon seems rather difficult. There are instances in which what had once been trap-dikes are found existing as mere empty fissures; and other instances in which empty fissures have been filled up by aqueous deposition from above. An instance of the one kind is adduced, as the reader may perhaps remember, in the "Elements" of Lyell, from M'Culloch's "Western Islands;" two contiguous dikes traversing sandstone in Skye are found existing to a considerable depth as mere hollow fissures. An instance of the other kind may be found, says M'Culloch, in a trap-rock in Mull, which is traversed by a dike that, among its other miscellaneous contents, incloses the trunk of a tree, converted into brown lignite. In cases of the first kind, the original dike, composed of a substance less suited to resist the action of the weather than the containing rock, has mouldered away, and left the vent from which it issued a mere hollow mould, in which the semblance of a dike might be cast, just as the decay and disappearance of the real crystal is supposed to have furnished a mould for the formation of the sandstone one. In cases of the second kind, we see the fictitious dike actually existing; it is the sandstone crystal moulded and consolidated, and, in short, ready for the museum. And we have but to suppose the conditions of the two classes of dikes united, we have but to suppose that the hollow filled by the aqueous deposition had been previously filled by an igneous injection, in order to account for all the phenomena of an igneous dike accompanying a merely aqueous one. We can scarce account in this way, however, for the formation of the dikes at Eathie, seeing that the shale in which they are included is

of so soft and decaying a character, that no igneous rock could of possibility be more so; nor, even were the case otherwise, could the upper portion of the dykes have existed as open chasms during the period in which the process of decay would have been taking place in the depths below. They would have infallibly filled up with the fragments detached from the sides and edges.

Mr. Strickland, in a paper on the subject in the "Transactions of the London Geological Society," states the problem very strongly. "The substance of these dikes is such," he says, "that it is impossible to refer them to a purely igneous origin;" and yet, however much “it may resemble an aqueous product," it is as impossible to doubt that the dikes themselves are genuine "intrusive dikes penetrating the Lias shale in all directions." He adds further, as his ultimate conclusion in the matter, that the "sedimentary structure of the rock forbids us to refer it to igneous injection from below;" and that, "notwithstanding the complete resemblance of these intrusive masses to ordinary plutonic dikes, we have no resource left but to refer them to aqueous deposition, filling up fissures which had been previously formed in the Lias." There is a peculiar rock in the neighborhood, which throws, I am of opinion, very considerable light on their origin. It is what may be termed a syenitic gneiss, abounding in minute crystals of hornblende, that impart to it a greenish hue; and in one place we find it upheaved so directly among the Lias beds, that it breaks their continuity, It raised them so high on its back, that the denuding agencies laid the back bare by sweeping them away. Let us but imagine that this disturbing rock began to rise under the earlier impulsions of the elevating agencies, and during the deposition of some one of the later secondary formations,