GRANITIC GNEISS AND SANDSTONE, WITH THE CONDITIONS OF
ON entering on the granitic rock, we find the strata, strangely disturbed and contorted, lying, in the course of a few yards, in almost every angle, and dipping in almost every direction. And not only must there have been a complexity of character in the disturbing forces, but the rock on which they acted must have been singularly susceptible of being disturbed. The strata of the sandstone were, at the period of their upheaval, the same brittle, rigid plates of solid stone that they are now. The strata of the granitic gneiss were characterized, on the contrary, during their earlier periods of disturbance, by a yielding flexibility: they were capable of being bent into sharp angles without breaking. We see them running in zig-zag lines along the precipices, now striking downwards, now ascending upwards, now curved like a relaxed Indian bow in one direction, now curved in a contrary one, like the same bow when fully bent. The strata of the sandstone, like a pile of glass-panes laid parallel, existed in a state in which they could be either raised in any given angle, or, if the acting forces were violent
and partial, broken up and shivered; whereas the granitic strata existed in the state of the same glass-panes brought to a bright red heat, and capable, from their extreme flexibility, of being bent and twisted in any direction. We find, too, that there occur occasional patches in which the lines of the stratification have been altogether obliterated. We can trace the strata with much distinctness on every side of these; but there is a gradual obscuration of the lines, and we see what was a granitic gneiss in one square yard of rock existing as a compact homogeneous mass in the next. The effect is exactly that which would be produced in the heated panes of my illustration, were the heat kept up until portions of them began to run; and the circumstance serves to throw light on some of the other phenomena of the gneiss. The stone, in its average specimens, is a ternary, consisting of red feldspar, white quartz, and a dingy-coloured mica; but no one, notwithstanding, could mistake it for a true granite. It has its granite veins, however; and these veins, truly such in some cases, are, in not a few others, mere strata of the gneiss, which have evidently been formed into granite where they lie. There are no marks of injection, — no accompanying disturbance: all their conditions, with the exception of their being true granites, are exactly those of the layers which repose over and under them. Now the homogeneous patches serve, as I have said, to throw light on the secret of the formation of these. In one important respect the granitic rocks differ widely among themselves. Some of them contain potass and soda in such large proportions, and have such a tendency to disintegrate, in consequence, that they furnish much less durable materials for building than the better sandstones; while others, of an almost indestructible quality, are devoid of these salts altogether. Potass and soda form powerful fluxes; and it seems at least natural to infer that, should wide tracts of granitic rock be exposed to
an intense but equable heat, the portions of the mass in which the fluxes exist in large proportions must pass into a much higher state of fluidity than the portions in which they are less abundant, or which are altogether devoid of them. Single strata and detached masses might thus come to be in the state of extremest fusion of which their substance was capable, and all their particles, disengaged, might be entering freely into the combinations peculiar to the plutonic rocks, when all around them continued to bear the semi-chemical, semi-mechanical characteristics of the metamorphic ones. Hence it is possibly the origin of some of those granite veins, open above, and terminating below in wedge-like points, which have so puzzled the Huttonians of a former age, and which have been so triumphantly referred to by their opponents as evidences that the granite had been precipitated by some aqueous solution.
OBSERVE these nodular masses of pale blue limestone, that seem as if they had cracked in some drying process, and had afterwards the cracks carefully filled up with a light-coloured cement. The flaws are occupied by a rich calcareous spar; and in the centre of each mass we find, in most instances, a large ill-preserved Ammonite, which has also its spar-filled cracks and fissures, as if it, too, had been burst asunder by the process which had rent the surrounding matrix. These nodular masses are the characteristic septaria or cement-stones of the Lias, so much used in England for maklng a hard, enduring mortar, that has the quality of setting under water. Their bluish-coloured portions are so largely charged with the argillaceous matter of the bed in which they occur, and contain, besides, so considerable a mixture of iron, that, refusing to slake like common lime,
they have to be crushed, after calcination, by mechanical means ; while
the fossil in the centre, and the semi-transpa rent spar of the cracks,
are composed of matter purely calcareous. And from this peculiar mixture this
cement seems to derive those setting qualities which render it of such value.
THE Ammonites of the upper beds of the Lias approach more to the type of
the Ammonite communis, being comparatively flat when viewed sectionally,
and having the whorls broadly visible, as in the Ionic volute; while the
Ammonites of the lower beds approach in type to the Ammonite heterophyllus,
— each succeeding whorl covering so largely the whorl immediately
under it, that the spiral line seems restricted to a minute hollow in the
centre, scarce equal in extent, in some specimens, to the twentieth part
of the entire area. In other words, the Ammonites of the Upper Lias in this
deposit represent, as a group, the true ammonite type; while in the Lower
Lias they approach more nearly as a group to the type of the nautilus. And
not only are they massier in form, but also absolutely larger in size. I
have found Ammonites in the more ponderous septaria, that fully doubled in
bulk any I ever saw in the upper shales. We occasionally find nodules
that, having formed in the outer rings of these larger shells, somewhat resemble
the rims of wheels, — in some cases, wheels of not very diminutive size.
BELEMNITES OF THE NORTHERN LIAS.
WE find the Belemnites of the lower deposit, like its Ammonites, of a
bulkier form than those of the upper beds.
The Belemnites abbreviatus and elongatus, both large, massy species, especially the former, are of common occurrence; while those most abundant in the upper beds are the Belemnites longissimus and penicillatus, both exceedingly slim species. It is worthy of remark, that Sir R. Murchison, in his list of fossils peculiar to the Lias as developed in the midland counties of England, specifies the Belemnites penicillatus as characteristic of its upper, and the Belemnites abbreviatus and elongatus of its lower division.
Is the reader acquainted with at once the largest and most curious of British Mollusca, — the cuttle-fish, —a creature which stands confessedly at the head of the great natural division to which it belongs? Independently of its intrinsic interest to the naturalist, it bears for the commentator and the man of letters an interest of an extrinsic and reflected kind. No other mollusc occupies so prominent a place in our literature. It is furnished with an ink-bag, from which, when pursued by an enemy, it ejects a dingy carbonaceous fluid, that darkens the water for yards around, and then escapes in the cloud, — like some Homeric hero worsted by his antagonist, but favoured by the gods, or some body of military retreating unseen from a lost field, under the cover of a smoking shot. And there has scarce arisen a controversy since the days of Cicero, in which the cuttle-fish, with its ink-bag, has not furnished some one of the controversialists with an illustration. It has attained to some celebrity, too, on another and altogether different account. That enormous monster, the kraken of Norway, of which our earlier geographers tell such surprising stories, was held to belong to this curious family. And though the monster has disappeared from the treatises of our naturalists
[APPENDIX. 289]for a full half-century, and from the pages of even our more credulous voyagers for at least a century more, it maintained its place as a real existence long enough to be assigned a permanent niche in our literature. It has been described as raising its vast arms out of the water to the height of tall forest-trees, and as stretching its knobbed and warted bulk, roughened with shells, and darkened with sea weed, for roods and furlongs together, — resembling nothing less extensive than some range of rocky skerries on some dangerous coast, or some long chain of sand-banks forming the bar of some great river. It was introduced to the reading world with much circumstantiality of detail, by an old Norwegian bishop (Eric Pontoppidan), as 'an animal the largest in creation, whose body rises above the surface of the water like a mountain, and its arms like the masts of ships.' And one of the French continuators of Buffon, — Denys Montfort, — regarding it as at least a possible exist ence, has given, in his history of Mollusca, a print of a colossal cuttle-fish hanging at the gunwale of a ship, and twisting its immense arms about the masts and rigging, — a feat which the cuttle-fish of the Indian seas is said some times to accomplish, if not with a ship, at least with a canoe. But nowhere does the kraken of Norway look half so imposing or half so poetical as in Milton. In palpable reference to the old bishop's 'largest animal in creation,' we find the poet describing, in one of his finest similes,_
Leviathan, which God of all his works
Created hugest that swim th' ocean stream:
Him haply slumb'ring on the Norway foam,
The pilot of some small night-founder'd skiff
Deeming some island, oft, as seamen tell,
With fixed anchor in his scaly rind,
Moors by his side under the lee, while night
Invests the sea, and wished morn delays.'
The existing cuttle-fish of our seas, though vastly less
imposing in its proportions than the kraken of Norway, is, as I have said, a very curious animal, — constituting, as it does, that highest link among Mollusca, in which creatures without a true back-bone or a true brain approach nearest, in completeness of structure and the sagacity of their instincts, to the vertebrata. All my readers on the sea-coast, especially such of them as live near sandy bays, or in the neighbourhood of salmon-fishings, must have frequently seen the species most abundant in our seas, — the common loligo or strollach (Loligo vulgaris) ; and almost all of them must have the recollection of having regarded it, when they first stumbled upon it in some solitary walk, as an extraordinary monster, worthy of the first place in a museum. 'The cuttle fish,' says Kirby, in his Bridgewater Treatise, 'is one of the most wonderful works of the Creator.' We have no creature at all approaching it in size, that departs so widely from the familiar every-day type of animal life, whether developed on the land or in the water.
A man buried to the neck in a sack, and prepared for such a race as Tennant
describes in his Anster Fair, is an exceedingly strange-looking
animal, but not half so strange-looking as a strollach. Let us just
try to improve him into one, and give, in this way, some idea of the animal
to those unacquainted with it. First, then, the sack must be brought to
a point at the bottom, as if the legs were sewed up tightly together, and
the corners left projecting so as to form two flobby fins; and further,
the sack must be a sack of pink, thickly speckled with red, and tolerably
open at the other end, where the neck and head protrude. So much for the
changes on the sack ; but the changes on the parts that rise out of the
sack must be of a much more extraordinary character. We must first obliterate
the face, and then, fixing on the crown of the head a large beak of black
horn, crooked as that of the parrot, we must remove the mouth to the opening
between the mandibles. Around the broad base of the beak
must we insert a circular ring of brain, as if this part of the animal had no other vocation than to take care of the mouth and its pertinents; and around the circular brain must we plant, as if on the coronal ring of the head, no fewer than ten long arms, each furnished with double rows of concave suckers, that resemble cups arranged on the plane of a nar row table. The tout ensemble must serve to remind one of the head of some Indian chief bearing a crown of tall feathers; and directly below the crown, where the cheeks, or rather the ears, had been, we must fix two immense eyes, huge enough to occupy what had been the whole sides of the face. Though the brain of an ordinary-sized loligo be scarcely larger than a ring for the little finger, its eyes are scarce smaller than those of an ox. To complete our cuttle-fish, we must insist as a condition that, when in motion, the metamorphosed sack-racer must either walk head downwards on his arms, or glide, like a boy descending an inclined plane on ice, feet foremost, with the point of his sack first, and his beak and arms last; or, in other words, that, reversing every ordinary circumstance of voluntary motion, he must make a snout or cut-water of his feet, and a long trailing tail of his arms and head. The cuttle-fish, when walking, always walks with its mouth nearer the earth than any other part of either head or body, and when swimming, always follows its tail, instead of being followed by it.
This last curious condition, though doubtless, on the whole, the best adapted
to the conformation and instincts of the creature, often proves fatal to
it, especially in calm weather and quiet inland firths, when not a ripple
breaks upon the shore, to warn that the shore is near. An enemy appears;
the creature ejects its cloud of ink, like a sharp-shooter discharging his
rifle ere he retreats; and then, darting away tail foremost under the cover,
it grounds itself high upon the beach, and perishes there. Few men have
walked much along the shores of a sheltered bay without witnessing a catastrophe
this kind. The last loligo I saw strand itself in this way was a large and very vigorous animal. The day was extremely calm; I heard a peculiar sound, — a squelch, if I may employ such a word; and there, a few yards away, was a loligo nearly two feet in length, high and dry upon the pebbles. I laid hold of it by the sheath or sack; and the loligo, in turn, laid hold of the pebbles, just as I have seen a boy, when borne off against his will by a stronger than himself; grasping fast to projecting door-posts and furniture. The pebbles were hard, smooth, and heavy, but the creature raised them with ease, by twining its flexile arms around them, and then forming a vacuum in each of its suckers. I subjected one of my hands to its grasp, and it seized fast hold; but though the suckers were still employed, it employed them on a different principle. Around the circular rim of each there is a fringe of minute thorns, hooked somewhat like those of the wild rose. In fastening on the hard smooth pebbles, these were overtopped by a fleshy membrane, much in the manner that the cushions of a cat's paw overtop its claws, when the animal is in a state of tranquillity; and, by means of the projecting membrane, the hollow inside was rendered air-tight, and the vacuum completed; but in dealing with the hand, a soft substance, the thorns were laid bare, like the claws of the cat when stretched out in anger, and at least a thousand minute prickles were fixed in the skin at once. They failed to penetrate it, for they were short, and individually not strong, but acting together and by hundreds, they took at least a very firm hold.
What follows the reader may deem barbarous; but the men who gulp down at
a sitting half a hundred live oysters to gratify their taste, will surely
forgive me the destruction of a single mollusc to gratify my curiosity.
I cut open the sack of the creature with a sharp penknife, and laid bare the
viscera. What a sight for Harvey when prosecuting, in the earlier stages,
his grand discovery of the circulation! There,
in the centre, was the yellow muscular heart propelling into the transparent tubular arteries the yellow blood. Beat — beat — beat; I could see the whole as in a glass model; and all I lacked were powers of vision nice enough to enable me to detect the fluid passing through the minuter arterial branches, and then returning by the veins to the two other hearts of the creature; for, strange to say, it is furnished with three. There is the yellow heart in the centre, and lying altogether detached from it, two other darker-coloured hearts at the sides! I cut a little deeper. There was the gizzard-like stomach, filled with fragments of minute mussel and crab shells; and there, inserted in the spongy, conical, yellowish-coloured liver, and somewhat resembling in form a Florence flask, the ink-bag distended, with its deep dark sepia, — the identical pigment sold under that name in our colour-shops, and so extensively used in landscape drawing by the limner. I once saw a pool of water, within the chamber of a salmon-wear, darkened by this substance almost to the consistence of ink. Where the bottom was laid dry, some fifteen or twenty cuttle-fish lay dead, some of them green, some. blue, some yellow; for it is one of the characteristics of the creature that, in passing into a state of decomposition, it assumes a succession of brilliant colours; but at one of the sides of the chamber, where there was a shallow pool, six or eight individuals, the sole survivors of the shoal, still retained their original pink tint, freckled with red, and went darting about in panic terror within their narrow confines, emitting ink at almost every dart, until the whole pool had become a deep solution of sepia. But I digress.
I next laid open the huge eyes of the stranded cuttle-fish. They were curious
organs, — more simple in their structure than those of any quadruped, or
even any fish, with which I am acquainted, but well adapted, I doubt not,
for the pur pose of seeing. A camera-obscura may be described as consisting
of two parts, — a lens in front, and a darkened chamber
behind; but in both the brute and human eye we find a third part added: there is a lens in the middle, a darkened chamber behind, and a lighted chamber, or rather vestibule, in front. Now this lighted vestibule — the cornea — is wanting in the eye of the cuttle-fish. The lens is placed in front, and the darkened chamber behind; the construction of the organ is that of a common camera-obscura, without aught additional. I found something worthy of remark, too, in the peculiar style in which the chamber is darkened. In the higher animals it may be described as a chamber hung with black velvet ; the pigmentum nigrum which covers it is of deepest black: but in the cuttle-fish it is a chamber hung with velvet, not of black, but of a dark purple hue; the pigmentum nigrum is of a purplish-red colour. There is something curious in marking this, as it were first, departure from an invariable condition of eyes of the more perfect structure, and in them tracing the peculiarity downwards through almost every shade of colour, to the emerald-like eye-specks of the pecten, and the still more rudimental red eye-specks of the star-fish. After examining the eyes, I next laid open, in all its length, from the neck to the point of the sack, the dorsal bone of the creature, — its internal shell I should rather say, for bone it has none. The form of the shell in this species is that of a feather equally developed in the web on both sides. It gives rigidity to the body, and furnishes the muscles with a fulcrum; and we find it composed, like all other shells, of a mixture of animal matter and carbonate of lime. In some of the genera it is much more complicated and rigid than in that to which the strollack belongs, consisting, instead of one, of numerous plates, and in form somewhat resembling a flat shallop with its cargo rising over the gunwale, or one of the valves of a pearl mussel occupied by the animal. Is my description of this curious creature too lengthy? The young geologist who sets himself to study the fossils of the Oolitic and
Cretaceous systems would be all the better for knowing a great deal more regarding it than I have told him here. He will discover that at least one-half the molluscous remains of these deposits, their belemnites, ammonites, nautili, nummulites, baculites, hamites, lituites, turrilites, and scaphites, belonged to the great natural class — singularly rich in its extinct orders and genera, though comparatively poor in its existing ones — which we find represented by the cuttle-fish.
AMONG its many extinct congeners, the order of the Belemnites was one of not the least curious. It has been remarked, that in the cuttle-fish, as we now find it, a greater number of distinct portions of the organization of creatures belonging to widely-separated divisions of the animal kingdom are to be seen united than in any other animal. Cut off its head immediately below the arms, and we have in the dissevered portion, with its ring of nerve, its central mouth, and its suckers, the true analogue of a star-fish. The radiated zoophyte lies before us. Some of its genera have their plated and jointed antennae placed above and below the eyes. The creature, so far as these organs give it a character, is no longer a zoophyte, but an insect or crustacean. But then there is the soft sac, with its fin-like appendages, the internal shell, and the yellow transparent blood. These are unequivocal characteristics of the molluse. Yes; but then there is a horny beak, and there a muscular gizzard. It must have laid the bird tinder contribution for these. There is, besides, a true tongue, and an organ for hearing; and, though one of the chambers be wanting, a singularly large and efficient eye. These organs are all borrowed from the vertebrata. And — as if to secure its claim to originality, not only in its combinations, but in its
parts — there are its three hearts, and its well-stored ink-bag, chattels that it could scarce have borrowed anywhere. It occupies, according to Cuvier, a sort of central place in the animal kingdom, where roads from all the various divisions converge, and the three hearts and the ink-bag mark, as it were, the point at which they meet. Extensive and wonderful, however, as its combination of parts may seem, its extinct congener the Belemnite added to the number at least one part more. Like that curious gelatinous zoophyte, the Dutch man-of-war (Physalia), it was furnished with a sailing apparatus. Not only could it swim tail foremost, and walk head downwards, like our existing cuttle-fish; but it could also raise itself to the surface of the water, and there, spreading out its sail of thin membrane, speed gaily away before the wind. Several of the existing congeners of the creature, such as the Argonauta Argo, are sailors still; but, unlike the Belemnite, or its analogue the cuttle-fish, they are furnished with external shells. They are sailors each in its own little boat, whereas the Belemnite was a sailor without a boat, — such a sailor as Franklin was, when, laying him self at full length in the water, he laid hold of the string of an elevated kite during a smart breeze, and, without effort on his own part, was drawn across a small lake by the impulsion of the wind above.
I have full in my view where I write, a shelf occupied with ranges of our
Scotch Belemnites of the Lias placed on end, and leaning against the wall,
like muskets in an armoury. A second shelf exhibits ranges of our Scotch
Belemnites of the Oolite. Ere adverting, however, to their specific differences,
— differences which their mode of arrangement renders apparent at a glance,
let me select for description an average specimen, as a type of the order.
Here, then, is the Belemnite elongatus, from the Upper Lias of Eathie.
The architect gives the proportions of his columns by a scale of diameters.
The height of the Tuscan column is equal to
seven, that of the Doric to eight, that of the Ionic to nine, and that of the Corinthian to ten diameters. In describing the proportions of the Belemnite, I shall borrow a hint from the architect, by making my scale one of diameters also; fixing my callipers, not at the base of the shaft, but one-fourth of its entire length higher up. Let the reader imagine a small cylindrical column of brown polished stone, diminishing from the base upwards for three-fourths of its height, much in the same proportions as one of the Grecian columns diminishes, and then in the remaining fourth suddenly sweeping to a point. Its length — eight inches in the present instance — is equal, like that of a Corinthian shaft, to ten of its diameters. Within this solid column we find an internal cone rising from the common base, the whole of which it occupies, and terminating in the apex, at about one-third the height of the whole. It is different in colour and structure from the brown pointed shaft at which it is included. The shaft or column shows as if it had been formed, like a dipped candle, by repeated accessions to its outer surface; whereas the internal cone shows that it has been formed by accessions to its base. The shaft seems to have grown as a tree grows, and exhibits its internal concentric rings crossed by lines radiating from the centre, just as the yearly rings of the tree are crossed by the medullary rays: the internal cone, on the contrary, was reared course after course, as a pyramid is built of ashlar, — with this difference, however, that it was the terminal course of the apex that was laid first, and that every succeeding course was added to the base. The entire Belemnite was originally of greater length than the specimen before us indicates; for the cone extended very considerably beyond the base of the column, and beyond the cone there was a still further prolongation of a kind of horny sheath, composed of the internal shell of an extinct order of cuttle-fish, its substitute for a vertebrate column; just as the existing loligo
has its thin elastic pen, and the existing sepia its stiffer and more complex bundle of calcareous plates. There are English specimens, in which the characteristic ink-bag may still be found resting on the base of the internal cone, giving evidence at once of the class of animals to which the fossil belonged, and that the column and cone must have been internal, not external, shells. Nature, though liberal to all her creatures, is no spendthrift. We find that to her naked Cephalopoda, such as the strollach and the sepia, she gives in the ink-bag an ability of hiding themselves in sudden darkness; but that to the shelled creatures of their class, such as the nautilus, she gives no ink-bag. For them the protecting shell is sufficient. The ink-bag of the Belemnite at once shows that it was a cuttle-fish, and that it was naked. Here, in a specimen from the Whitby Lias, we may see the bag still charged with its ink; and so slight is the change induced by untold centuries, in the nature of the carbonaceous substance which composed the latter, that, after having scraped it down, and diluted it with water, we may still use it as a pigment. We find it stated by Buckland, that the tinting of a drawing made with fossil ink at his request by his friend Francis Chantrey was pronounced by a celebrated painter, unacquainted with the secret of its origin, as peculiarly agreeable and well-toned.
But the Belemnite, with its horny prolongation, was not merely a sort of
stiffener introduced into the body of the creature to give it rigidity, —
as the seamstress introduces, for a similar purpose, bits of wire and whalebone
into her pieces of dress, or as the pen exists in the strollach:
the stony column, and its internal cone, constituted, besides, the sailing
organs of the creature, — the cone forming its floating apparatus, and
the column its ballast. The cone, as I have said, consists of a number
of layers, ranged parallel to its base, like courses of ashlar in a pyramid.
We find each
layer, when detached, exactly resembling a thick patent watch-glass, concave on its under, convex on its upper, surface. Now, each of these formed, in its original state, not a solid mass, but a hollow, thinly partitioned chamber or storey; and, perforating the entire range of storeys from apex to base, there was a cylindrical pipe, just as the reader must have seen the cylindrical case of a turnpike stair passing upwards through the storeys of some ancient tower from bottom to top. And this pipe was the siphuncle or pump through which the creature regulated its specific gravity, and sank to the bottom or rose to the surface, just as it willed. Mr. J. S. Miller, well known for his labours among the Grinoidea, mentions, in his paper on Belemnites, an interesting experiment with regard to the cone. He extracted it carefully from one of his specimens, and then inserting in the hollow of the stony column which it had occupied, a cone of oiled paper filled with cotton, he placed the specimen in water, and found the buoyancy of the cone compensating so completely for the density of the column, that the whole floated. Now, to demonstrate the use of the ballasting column, let us imagine a sail raised over the cone, and the whole sent to sea in a high wind. Has the reader ever sailed, when a boy, his mimic ship, and does he remember how imperative it was that there should be lead on the keel? The stony column is the lead here; and from the form of the creature, as indicated in the entirer specimens, some such internal ballasting seems to have been as essential to preserve its upright position as the lead is to the boy's ship. There are, however, but few of our naturalists who believe, with Mr. J. S. Miller, that the column was originally the dense and solid body it is now. Lamarck held that, like the bone of the existing sepia, it was of 'a spongy and cellular texture;' Parkinson, that it was 'porous or cork-like;' and Buckland, that 'the idea of its having been heavy, solid, and stony, while it formed part of a
living and floating sepia, is contrary to all analogy.' With an eye to the question, I have succeeded in collecting a number of specimens, which, when in their recent state, had been crushed or broken; and I am disposed to hold, from the appearance of the fractures in every case, that, notwith standing the authorities arrayed against him, Miller's view is the right one. The stony column, though it must have been somewhat less brittle in its recent than in its fossil state, — for it contained its numerous thin plates of horn, tenacious, as is natural to the substance, in a considerable degree, — was yet brittle enough to break across at very low angles, and to exhibit on the side to which the force had been applied, its yawning cracks and fissures, though on the opposite side the wrinkled surface generally indicates a tag of adhesion. In the cases, too, in which the Belernnite had been broken into fragments, I have found every detached portion presenting its hard, sharp angles, and existing as a brittle calcareous body, however soft and chalky the condition of the more delicate shells of the deposit in which it occurred. Nor do I know that analogy is very directly opposed to the supposition that the column might have existed in the creature in its stony state. If two solid calcareous substances, quite as hard and dense as any fossil Belemnite, exist within the head of the recent cod and haddock, why might not one solid calcareous substance have existed within the body of an extinct order of cuttle fish?
I have found considerable difficulty in classing, according to their species, the Belemnites of the Lias. I soon exhausted the species enumerated as peculiar to the formation by Miller, and found a great many others. They divide naturally into two well-marked families, — the specimens of a numerous family, that, like the Belemnite elongatus, are broadest at the base, and diminish as they approach the apex, — while the specimens of a family considerably less
numerous, like the Belemnite fusiformis, resemble spear heads, in
being broadest near the middle, and in diminishing toward both ends. In subdividing
these great families, various principles of classification have been adopted.
There are grooves, single in some species, double, and even triple, in others;
extending from the apex downwards in some, extending from the base upwards
in others ; and these have been regarded by Phillips, — the geologist who
has most thoroughly studied the subject, — as constituting valuable characteristics
not only of species, but of genera and formations. Miller took into account,
as principles of classification, not only the general form, but even the
comparative transparency or opacity, of the column, — marks selected in accordance
with the belief that the column was originally the solid substance it is
now. The order furnishes, doubtless, its various marks of specific arrangement.
I have even found the hint borrowed from the architect, of taking the proportions
of species by their diameters, not without its value. In measuring, for instance,
four well-preserved specimens of the Belemnite abbreviatus, one of
the bulkiest which occurs in our Scotch Lias, and whose average length is
six inches, I found that two of the four contained 5 1/2 diameters, one 5
1/4 diameters, and one 5 3/4 diameters; while another bulky Belemnite
of the Scotch Oolite, not yet named apparently, whose average length is 3
1/2 inches, contains only 3 1/2 diameters, and strikes at once as
specifically different from the others. Equally striking is the specific
difference of the Belemnite elongatus, which contains from nine to
ten diameters, — of another nameless species which contains from twelve to
thirteen diameters, — of another which contains from fifteen to sixteen diameters,
— of another, agreeing in its proportions with the Belemnite longissimus
of Miller, which contains from eighteen to twenty diameters, — of another
which contains from twenty three to twenty-four diameters, — and of yet another,
and slender as a heckle-pin, which contains from thirty to thirty-two diameters. My rule of classification must of course be regarded as merely a subsidiary one. There are species which it does not distinguish : it does not distinguish, for instance, the Belemnite sulcatus of our Scotch Lias, whose average length is six inches, from the Belemnite elongatus, whose average length is eight. Both agree in containing from nine to ten diameters, though in form and appearance they are strikingly different, — the adjuncatus being much more pointed at the apex than the other, much more finely polished on the surface, and furnished with a deeper groove. As a subsidiary rule, however, I have found the rule of the diameters a useful one. It has enabled me to form a 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 sprang 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.
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 sauruns. 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 neighbour 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; 'was
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 ena melled scales
of that curious fish the bony pike, so common, as you are aware, in our
South American rivers.'
THERE are appearances in connexion 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 dikes of what seems a greyish-coloured trap, extremely obstinate in yielding to the hammer, and which stand up among the softer shales like the walls of some ruined villa 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 enclose the shale in slim insulated strips, as a river encloses 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 indur ated and venous 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'Cul loch, in a trap rock
in Mull, which is traversed by a dike that, among its other miscellaneous
contents, encloses 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 con taming 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
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 dikes 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 fiagments 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 neighbourhood, 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, as
the precursor of the granitic range, — that the superincumbent Lias, already
existing in its present consolidated state, opened into yawning rents and
fissures over it, as the earth opened in Calabria during the great earthquake,
— and that the loose sand and calcareous matter which formed the sea-bottom
at the time, borne downwards by the rushing water, suddenly filled up these
rents, ere the yielding matrix had time to lose any of its steepness of
side or sharpness of edge, which it could not have failed to have done had
the process been a slow one. The sandstone dikes, apparently Oolitic, mark,
it is probable, the first operations of those upheaving agencies to which
we owe the elevation of the granitic wall, and which, ere they accomplished
their work, may have been active during occasional intervals for a series
of ages. I am not of opinion that the accompanying marks of alteration among
the shales and limestones of the beds are sufficiently unequivocal to render
imperative some more fiery theory.