CONCERNING CERTAIN PETRIFIED ZOOPHYTES, NOW GENERALLY SUPPOSED TO BE EXTINCT.
CONCERNING CERTAIN PETRIFIED ZOOPHYTES, NOW GENERALLY SUPPOSED TO BE EXTINCT.
The petrifaction of an animal form or structure has always appeared to me a most singular process in Nature. The change of such substances as cellular tissue, or fish-bone, or cartilage, or a light, leathery skin, into minerals such as silex and agate, seems at first like magic. Scott, when describing the “foliaged tracery” in the east oriel of Melrose Abbey, tells his reader:
“Thou wouldst have thought some fairy’s hand’Twixt poplars straight the osier wandIn many a freakish knot had twined,Then framed a spell when the work was done,And changed the willow wreaths to stone.”
“Thou wouldst have thought some fairy’s hand’Twixt poplars straight the osier wandIn many a freakish knot had twined,Then framed a spell when the work was done,And changed the willow wreaths to stone.”
“Thou wouldst have thought some fairy’s hand
’Twixt poplars straight the osier wand
In many a freakish knot had twined,
Then framed a spell when the work was done,
And changed the willow wreaths to stone.”
But there is no magic in Nature; and when we meetwith undoubted phenomena, however strange they may appear, in any department of her realm, we must behave ourselves like matter-of-fact persons and set about accounting for them logically. In a genuine petrifaction there are two ways of doing this, or, in other words, there are two different modes in which Nature may have acted so as to produce the result which we are considering. One of these is that of a simplesubstitution; the particles of one substance being gradually removed, and those of another taking their place. This must have been the process which obtained in many well-known instances: as, for example, when the thin, leathery shell or husk of an echinus is found perfectly rendered, both as to its general outline and minute markings, in solid flint or limestone. We feel quite sure that the original husk has perished; but here is its second self.
The other mode is that of actualtransmutation, wherein no part of the original substance is destroyed or removed, but its physical conditions undergo a total change, by means of either infiltration, or crystallization, or perhaps both of them combined. This process has obtained in such cases as a petrified shark’s tooth, or a fossil trilobite from the Wenlock.
The tooth, which was once bone, is now a kind of metallic stone: the trilobite once, as we suppose, shell and cartilage, is now a something between limestone and cast-iron. And this change is very wonderful; but, as was said above, there is no magic in it, no more than in the hardening of an infant’s skull, or the solidifying of the arm and leg-bones by the absorption of phosphate of lime. Besides, the stone and metal now present are still something different from what we ordinarily mean by those terms: the petrified tooth is not like a flint-stone, neither could you cut horse-shoe nails out of the trilobite.
In fact, everyrealprocess has a character of its own: a something which distinguishes it from any other, despite of general resemblances up to a certain point.
Petrifaction, then, being assumed, as an operation which has really taken place after one way or another, it falls next to be considered, what was the original nature of these fossils? I mean the objects which we find thus preserved in our seaside pebbles. What was the department in Creation to which they belonged? Was itanimalorvegetablebefore it thus became altogethermineral?
For myself, I will at once say that I have no doubt it was animal; but not an animal of a very high order. The specimens which I now possess, and which are all of them chosen, some of themrare, I should assign to such creatures as the “zoophytes” or “polyps,” both radiated and globular. And I know of nothing, among many hundreds of specimens gathered from a dozen different beaches, which presents the evidence of having belonged to vegetable organization, with the exception of sundry varieties of petrified wood, which speak for themselves, and could not be mistaken by anybody.
I will now state two or three reasons, which to my own mind are conclusive, for the above decision.
In the first place, then, the structures here perpetuated in stone are of great delicacy, and they have been immersed in ancient seas, as is testified by the localities in which they are obtained. Now vegetable structure as fine as this, if immersed long enough for any such change to come in question, must have utterly perished by maceration, and then the petrifaction could not have taken place. I know that part of the stem (and I think fruit) of one species of “conifer” has been found in the Isle of Wight in the condition of a fossil; but this belongedto a hardy class of plants, and the lobes or plates which composed its bark and husk are themselves highly siliceous, to say nothing of the presence of iron in the rind of most of these stems. So that the process would be a long one, and the fibrous material of the tree would stand it well. But in these pebbles some of the threads or tubes run from the size of small twine to that of the rays in a spider’s web; and no vegetable substance with which I am acquainted, excepting the filaments of “asbestos” (which is a vegetatingmineral) in rock-crystal, could abide and retain its form, so as to allow of the changes by infiltration or otherwise which have passed upon the original structure.
If it be said in reply to this, that we have the exquisitely delicate “dendritic” markings, as of leaves and filaments of shrubs or sea-weed, in the heart of the white chalcedony “mocha-stones” from the East, the answer is evident: these are notreallyvegetable traces, but onlyresemblesuch in their configuration and colours. They are simply shoots and ramifications of a metal,—as iron or manganese. Those in the “weed-agate” of India, which exactly resemble sprays of fine sea-weed, are produced by “delessite.”
Indeed, it is both diverting and instructive to observe how Nature permits, and even seems to abound in, curious coincidences and striking resemblances between things of entirely diverse character. The dried polyp, called “encrinoid echinoderm,” bears a wonderful likeness to one species of Indian corn. (See the plate at p. 137 of Mr. Rymer Jones’s beautiful work on “The Animal Kingdom.”) And the other day, when I was enjoying a leisure hour in the British Museum, I suddenly remarked that the “carapace” (back-shell) of the splendid fossil specimen of the “Holoptychius nobilissimus” in one of the cases might serve for a sketch of the back of acapercailzie, where the grey and purple feathers overlap one another. Yet here is norealconnection whatever. Only Dame Nature had gone to play.
Secondly.The preservation of these “polyp” forms, in the manner in which theyhavebeen preserved, seems to me to be due to a feature or circumstance which is strictly animal and not vegetable. I refer to the fact of the creature, while it was alive,inhabiting a house, a house built by himself, or emanating from his own substance. For, just as we could know but little of the existence or habits of “shell-fish,” were it not for theirshells, so I think we may assume that thechoanitemust, when alive, have dwelt in a tough, horny “coperculum,” answering to the shape of his body and the number of his “polyps” (if he was acompoundcreature), because otherwise he would have been like a jelly-fish or naked slug, and his “polypary” could not have been preserved in a stony fossil. Of course, whatever was merely flesh, or adipose matter, has long since perished; but thehouseor shell in which it whilome dwelt remains. Thus, the “echinus” built himself adome, such a residence as ahedgehogwould require to live comfortably in, and through the various orifices of which his spines could be protruded at pleasure. The “ammonite,” being shaped like asnake, preferred living in a shell of that form, where the creature when coiled up was safe. The “alcyonite” had a more exquisite taste in house-building, answering, we may be sure, to the complex and beautiful structure with which the great Creator had endowed him. His home was a palace, containing long galleries and secret doors and wheel-windows; and here some of the delicate tubes are fringed at their extremities like the petals of a flower.
The antiquity of these formations may be very great,we can scarcely tell how far removed from our own era. For, while the zoophyte itself is of a perishable nature, we are acquainted with no substance more durable (if we except the gems) than that calcareous matter of which these tubes and plates were formed, when once it has been subjected to processes of infiltration by crystallizing mineral and metallic oxides.
Now, I think this argument a very strong one; in fact, although simple, almost unanswerable. For noplantdwells thus in a house. We have the plant itself, but nothing more; and if this be not capable, and I hold it to be incapable, of sustaining the most vehement mineralizing process in the crucible of Nature, its history must be a brief one, and excepting in the dark “lithographs” of the coal-measures, its memory must pass away. I have already allowed an exceptionable case in favour of theconifers, which, be it observed, nowise resemble anything portrayed in siliceous pebbles, and it is remarkable how much this class of plants predominates in the COAL.
I have always been suspicious of what are called “vegetable petrifactions.” I examined those at Tivoli, near Rome, in the year 1845, and I made up my mindthat they are simpleincrustations. In like manner, many of the buildings at Pæstum are constructed with a kind of “travertine” taken from the bed of a neighbouring river, and which rapidly incrusts any solid objects submitted to the action of its waters. But the truth is, the vegetable pipe or “straw” remains for a while, owing to the silex which entered into its composition while the plant was growing. After some years thestrawdecays, and there is a hole or depression in that part of the pillar or pediment. On the other hand, a calcareous “menstruum,” imbibing silex and iron, hardens into a substance which, like the best mortar or cement used in building, will sometimes outlast even the blocks of limestone or oolite which it was put to bind together.
Thirdly.Animal organization, such even as these polyps possessed, renders the phenomena much more intelligible. Our best authorities in such matters tell us that “insectshave neither lungs nor branchiæ; but in them the air passes intoa system of tubes, whose structure resembles that of an elastic webbing.” And again, “Theannelidspossess anuninterrupted circulation.” And again, “In the ‘Nymphon’ and ‘Pycnogonum’molluscs, which are crustaceans having considerable resemblance to certain of our field spiders, the intestinepenetrates to the very extremitiesof the feet and claws.”—Animal Kingdom.Now here are cited some of the very desiderata which I should have named, had I been asked what conditions were neededà priorifor such petrifactions to occur. I will only add, under this head, that a fineannelidoccurs in the blue agate off Eastbourne; that a “myriapod,” which is among the chromo plates of this volume, has all the characteristics ofinsectlife and motion; and that aspideris the nearest thing I know of, in some respects, to what the “choanite” must have been when that mollusc condensed himself from a cylinder to a sphere. Perhaps, however, the strongest clause in this part of the argument may be drawn from the “sponges.” Here the creature itself, wonderful to relate, is aviscous fluid, and the intricate mansion which he inhabits is a globose, horny skeleton, perforated with endless small tubes opening into wider galleries. There was, however, in the perfect animal, I am assured, one main central cavity, which gave strength and unity to the entire fabric by the plan of its walls, and, perhaps, by a main valve. Throughoutthe whole of this hydraulic system the sea-water, on the circulation of which the zoophyte depended for life and health, could be pumped to and fro at pleasure. And, evidently, when the “habitat” of such a creature was suddenly invaded by a siliceous crystalline solution, extinction of the animal and a petrifying investment of his abode would be simultaneous.
Lastly.If the objects here petrified had been vegetable in their extraction, should we not, with the aid of the microscope, be able to identify them? But this I have never yet succeeded in doing; yet all the petrified “woods” are well known. I have myself obtained slabs of the “acacia” from the coast of South Devon; of the “beech,” in Sussex; of coniferous wood almost everywhere. And, what is more to the purpose, though the petrifaction in such cases is deep and perfect, no one looking upon it could doubt for a moment that the original structure had been that of wood from a forest-tree. Agatized as it is, and penetrated here and there by metallic colours, and shot with rays of jasper, the lines in its fabric revealthe texture of wood.
I may mention here, that every one who walks our beaches, with a view to the collection of fossil specimens,will do well to carry in his or her pocket a good lens, of large external diameter; mine measures about two inches across, and I may truly say it has saved me a world of trouble, besides affording me much satisfaction at odd moments in the scrutiny of pebbles of different kinds and textures.
Before closing this chapter I may be permitted to draw the reader’s attention to a theory held by the late Dr. Mantell. I cannot, at this moment, lay my hand upon the volume in which it occurs, but I am pretty sure it will be found in his “Geology of the Isle of Wight:” a book which, for elegance of composition, and sound information, can hardly be too much commended; though a resident lapidary in Sandowndidonce say to me, while thumbing the pages of a well-worn copy, “Ah, sir! if the Doctor had comehereand stayed a week instead of listening only to what those fellows told him in Ryde, I could have shown him something which he doesn’t seem to know, as to how the bit of coast runs hereabouts.” Dr. Mantell’s idea was this: he held that when a mollusc was subjected to the first stage in the petrifying process, there was, in the dying of the creature, some effusion of blood (orquasi-blood), and that this, being the verypith and strength of the animal’s system, would, in many cases, tinge the future stone indelibly. He carried this notion so far as to assign some dark blotches, apparent in the masonry of a wall, to such a source as being their most probable cause; and he gave to the thing itself the graphic title ofMolluskite. In this view I will only add that I am inclined to agree with him; and in my “myriapod,” already referred to, there is a blood-red spot which pierces through the stone, appearing on both sides, and which I at first supposed to be a piece of “shell-lac,” but I now rather regard it as the trace left of himself by some marauding “pholas,” who, after drilling a hole through the solid pebble, found his own grave there.
ON THE LITORAL LABOURS OF THE OCEAN, AND ON SEASIDE SPORTS.
ON THE LITORAL LABOURS OF THE OCEAN, AND ON SEASIDE SPORTS.
The more I consider the various phenomena occurring from time to time on the dry land, and the more opportunity I have of observing for myself simple facts in geology, the more I am struck at once with the truthfulness and theunexpectedness—if I may use such a word—of the assertion which Moses makes in the 1st chapter of Genesis, that the appearance of the “dry land” was due to “the gathering together of the waters unto one place.”
The assertion has an unexpected (à priori) character; for continents and tracts of dry land do not, on the face of them, suggest the idea of any recent presence of incumbent masses of salt water—perhaps miles in depth. But it is eminently truthful, for it is a key to many anabstruse problem in Nature, and a confirmation of every sound and enlarged view of the past history of this globe.
The ocean has been busily at work—in old times, inland; in later times, coastwise; in all times subterraneously. This last point is proved by the volcanoes, and that in a twofold argument. Such volcanoes as are now extinct, are so because they have lost all communication with the sea; such of them as are active, are so because they draw supplies of salt-water from the nearest part of the ocean, and this they can only do subterraneously.
But in speaking of the labours of the ocean, I shall confine myself to the seashore, as the scope of this little volume does not go beyond that region. The point where sea and land meet is the critical point for all observers of Nature. Here the disciple of geology should serve his apprenticeship, and if he cannot accumulate facts, and glean a kind of inspiration here, he cannot do so anywhere. Moreover here, better, we think, than in any inland scenery, Man can muse and meditate. That ever-varying curved line of moisture on the shore depicts the fluctuating changes which momentarily visit his “little day;” the tide running in is the flood of his early life; the tide running out is the ebb of his decliningyears; the vast sweep of the coast, backed by the upland ranges and everlasting hills, and itself only lost to sight in the far horizon, tells of a steadfast future, an immutable eternity.
Above all, those who desire to note epochs in the flight of Time, and to set up way-marks in the Earth’s chronology, must study the line of the sea-coast, the ancient and the modern, for here, if anywhere, the dial-plate is uncovered, and the shadow of the gnomon may be traced through some seconds of the enormous day which has witnessed the existence of the heavens and the earth.
I have already, in my opening chapter, remarked how the sea brings down, in the course of ages, many a pebbly beach from cliff and causeway. But I am far from assuming, therefore, thatallthe pebbles of a beach come from the land. The usual bottom of the sea is, indeed, no pebbly shore; but there are many submerged rocks of sandstone and oolite, out of whose ribs and crevices, from time to time, fossils may be washed, just as our own chalk-cliffs, the main resort of the siliceous pebbles, were themselves laid down in deep seas. And the salt water, which is always acting gradually to dissolvecertain rocks, when it removes portions of these from the edges and promontories, will occasionally bring their contents to shore. But these results, although interesting to those who maybe searching after pebbles (and a deep-sea pebble is a prize), were not what I pointed at when I spoke of the labours of the ocean.
I have frequently walked the shore, and observed the colour of the waves, after what is termed a “ground swell,” which had lasted, perhaps, for thirty or forty hours. The cerulean hue is then gone, and to it has succeeded, in certain localities, an opaque chalky tinge, showing that the water is now heavily charged with lime. Also fragments of shells rolled together are united with heavy masses of sand, and sometimes of broken pumice-stone, and a kind of rough marl is rapidly formed, and left on the beach. After a gale, and succeeding “swell,” I have met with these imperfect boulders, varying in size from that of a man’s fist to some larger than his head. At the same time, any low ranges of littoral rocks become crusted over with the superabundant lime, being more than the waves will long hold in solution; and a coating is thus given to such rocks which is sometimesas hard as is the native limestone itself, a few weeks’ exposure to the sun and air sufficing to effect this.
Some fourteen years ago, I had an opportunity, when in Sicily, of examining a portion of the coast between Messina and Catania, and I regret that I did not avail myself of it more heartily. But I have seen M. Quatrefage’s book on this subject, and his observations, most carefully and laboriously conducted, may almost be said to close that part of the subject, as far as any prospect of eliciting fresh information is concerned. I think he measured some of the long reefs, and the evident increaseby incrustationextended for many miles of the coast-line, and was of considerable thickness. I have observed the same “masonic” phenomenon off the coast of St. Andrews, in Fifeshire, when swimming out among the weedy rocks, and afterwards climbing to the shore. I then thought it was the work of marine insects, as I had heard of molluscs building causeways of tubes of limestone, but I incline now to think it was the sea doing it, as they say, atfirst-hand. The sea, however, does a great deal in the same line at second-hand, by means, chiefly, of two species of zoanthoid polyps. Of theselittle creatures, one kind constructs the bases of coral islands, and another the summits (at the least) of the madrepore reefs. It is impossible to doubt that by labours so patiently carried on, and so widely diffused, some beneficent purpose is aimed at and attained by Providence. Perhaps they operate, finally, to warn the shipping of adventurous merchants from entering certain dangerous bays and straits; and if the humble madrepore has got a bad name through this, as though he had made the danger, he certainly suffers unjustly, for what real difference, as to ultimate and assured safety, can a few inches more of water in such places make? Far better to raise an impassable bar across the way at once, and proclaim, “no thoroughfare!”
Then the ocean supplies a great market, much the greatest in the world. I do not know the proportion of persons in Central Europe who live on fish to those who live on meat, but I think, in both Northern and Southern Europe, the former exceed the latter. In Connemara, on the western coast of Ireland, and in the Scotch highlands of Argyle and Inverness, fish is decidedly the staple article of diet, as far as animal food is concerned. I believe the same is true of Cornwall and part of Devon.The herring, the pilchard, the haddock, the cod, and the salmon—to say nothing of the sole and other flat-fish—feed millions of persons, and, with the help of oatmeal, barley-cakes, and (in a good year) potatoes, feed them well. Shell-fish are also no mean item, and are sometimes the most refreshing of all dishes, especially at the supper-table. Now the sea, it must be remembered, does all this for man without harrowing, ploughing, or sowing. The fisherman’s net may be said toreap, that is all.
Again, if jewels be of any real value, what is the value (among such) of a collar of faultless pearls? what is there among minerals, so pure, so exquisitely beautiful, whether we regard their tint or their form? These are the spontaneous production of a humble shell-fish; some say, an offering from the creature when he has been wounded. If so, men may here learn a lesson in kind, and return good for evil to those who persecute them.
Again, the ocean isourdefence: long may it prove so!
“Britannia needs no bulwark,No towers along the steep,Her march is o’er the mountain wave,Her home is on the deep.”
“Britannia needs no bulwark,No towers along the steep,Her march is o’er the mountain wave,Her home is on the deep.”
“Britannia needs no bulwark,
No towers along the steep,
Her march is o’er the mountain wave,
Her home is on the deep.”
No doubt, since man is a creature wholivesupon thedry land, the land is on the whole the most valuable; but what would the land be without the sea? Nay, to go no further, how could we exist in summer and autumn, if deprived of the sea-breezes? For myself, though naturally fond of field-sports, and delighting in botanical and entomological pursuits, I know of no treat equal to that of a seaside ramble in the month, say, of September or October.
Now let us consider how very little mischief the ocean does us. Much fewer people die of what are called “casualties” by sea, than of those by land. The truth is, we always hear of such as are lost at sea, because of the loss ofthe ship, which involves a question of insurance-money; but of deaths inland, especially in far countries, and if belonging to strange peoples or savage tribes, we perchance scarce hear at all. YEH, the Chinese Commissioner, killed, it was said, 70,000 persons in the course of his brief career, forpoliticalreasons. How long would it take for 70,000 persons to perish by storms or accidents at sea, in the usual course of things, in one small part of the globe?
A wreck, it must be allowed, is a terrible thing; but so is a house on fire, or a flood up the country.
The sea, moreover, labours to help the land in other ways, some of them singular enough. Many thousands of poor unproductive acres have, in these last ten years, been rendered rich and fertile by supplies of GUANO. And whence did we get the guano? why, from thesea-fowl, and from a barren rock in the bosom of the seas! This is no trifling benefit to reap from the “desert sea.”
What a beautiful thing isglass, and how indispensable it has become to us! Perhaps no other material can be insured to beperfectlyclean and pure for drinking out of. For many years our glass-works depended mainly upon a constant supply ofkelpfrom the Orkneys, and even now they cannot dispense with the sea-sand.
The porcelain mills in Staffordshire and elsewhere are very glad to obtain a cartload of pebbles from the beach. These go to the “crushing” department; and if among them there are, as there are pretty sure to be, a dozen lumps of chalcedony, the material of the next batch of teacups will be unusually fine, provided some one who understands thempicksthe stones first. Indeed, if I had no preferable occupation in this world, I have often thought I would collect the rough agates and chalcedonies from sundry localities I wot of, and fabricate abiscuitof my own, as the king of Saxony does at Meissen. But though I have not the leisure for this, others may have; and so I mention it here.
Especially I incline to think that a splendid kind of “Wedgewood” ware would result from the crushing of certain jaspers, for I suppose their colours would not fade in the furnace.
Then, the seaside visit, I must not omit to mention, can be enlivened by sundry local pursuits and amusements. Besides the pleasures of a sailing-boat, and a run with the “dredge” and the “dipping-net,” there is the exciting march of the Shrimper, knee-deep in the wave, pushing the hoop-net before him, and every now and then halting to fill his front pocket with the silvery jumpers. If there are rocks near at hand, there will belobster-potsto visit; and the habits and deportment of a live lobster are among the most curious in creation. In agility and cunning he surpasses even a salmon. Also, for the benefit of those who at all regard what they eat—and he who disregards it is a goose—I may just venture to hint that areallobster-salad (London confectioners have a way of sellingshamones,) is a dish worthy theirserious attention: Barclay’s stout being not a bad accompaniment.
But the above will sound to some persons too “Epicurean.” O gentle reader, do you love moonlight? and if you have ever admired the reflection of that planet in a lake or river, what will you say to it when you contemplate it in Sandown Bay? Culver on one side, looking as if it were of green glass, and the cliffs of Shanklin on the other resembling walls and pillars of porphyry! Or is your taste for the sterner beauty of storms and angry seas? Then visit Blackgang Chine late in winter, and you may “sup full of horrors.” The appearance of the waves below, as they come in over that fatal “race,” and the aspect of the earth and the heavens above, when the lightning darts from “St. Catherine’s head” and sweeps like a destroying Angel down the chasm of the Chine, yield together perhaps the grandest picture of desolation and terror that English scenery ever shows.
There are persons still living who are unwillingto speakof the fearful tempest they witnessed on that coast when the Clarendon was lost.
Lastly, to return to our “pebbles,” the sea is an indefatigable agent in the partly mechanical, partly chemical, work of infiltration; a process to which both the fine texture and varied colours of these agatized fossils are mainly due.
But of this I must treat in the chapter which follows.
Enough, for the present, of the ocean itself—of its labours and its sports. But, as some readers lovea comparison, and hold that every theme grows dull without this, I will quote from the lips of a great traveller, whom it was once my luck to meet, his opinion of the rival claims of the Desert, to that admiration which we islanders lavish on the heaving Ocean and the winding Shore. I cannot pretend to remember his very words; but he was eloquent as the son of Laertes, and he made me long to visit the East. He said that the Desert was “another world,” more marvellous than this of our land and sea: it was a home and a domain, like the former; yet was it waste and boundless as the latter. I asked about thesands. “Vast, beyond computation.” “And the material?” “Powdered quartz, all of it. Quartz mountains, crushed, and pulverized, and sifted!” The reddish hue is from the peroxide of iron. No particleof anything like organized matter has ever been detected in its composition. The caravan-camels which drop and die daily on their hot march, as they have done for centuries, leave their skeletons, after the vulture’s inquest is over, to bleach upon the surface; and, in the course of a season or two, these bones must turn to an impalpable powder: but that does not mix with the sand, or phosphate of lime would at once be found on analyzing it.
Then he spoke of the sunrise, and the glowing sunset; and of the delicious hours of night; and of tent-life in the Desert; and of wandering Arabs, who revere the grave and silent man; and of the charms of an encampment in some green “oasis;” and then, strongest commendation of all, he said, “I am going back, among the children of the Desert!”
CONCERNING CERTAIN NATURAL PHENOMENA.—ORIGIN OF THE DIAMOND.—FORMATION AND COLOURING OF GEMS.—INFILTRATION OF PEBBLES.—CAUSE OF TRANSPARENCY.—INTEGRITY OF THE FOSSIL-NODULES.—THEORY OF THE SHATTERED FLINTS.—CONCLUDING OBSERVATIONS.
CONCERNING CERTAIN NATURAL PHENOMENA.—ORIGIN OF THE DIAMOND.—FORMATION AND COLOURING OF GEMS.—INFILTRATION OF PEBBLES.—CAUSE OF TRANSPARENCY.—INTEGRITY OF THE FOSSIL-NODULES.—THEORY OF THE SHATTERED FLINTS.—CONCLUDING OBSERVATIONS.
The charm which wins and rivets our attention in such pursuits as those of Geology or Mineralogy, is not that the phenomena which we meet with are capable of being classified, and of forming a scientific system. All this is, no doubt, one day instructive and interesting; but it was an afterthought, the result of experiment. The first charm lay in that silent mystery which broods over every part of creation, a veil as yet unpenetrated by Science: it lay in our instinctive consciousness that Nature, in what are, perhaps, her simplest movements, still transcends all the master-pieces of Art.
Take, for instance, the crystalline gems. These are the most remarkable substances with which we are acquainted; they are also among the most simple. Chemically speaking, the metals and gases may claim to be regarded as simpler bodies; but then it must be remembered that we do not meet with them in nature thus unmixed. Gases vary, both in volume and character, every instant; and ordinary metallic ores are penetrated and disguised by foreign matter; whereas faultless crystals, once perfected, appear to be unalterable.
Some of these, as the DIAMOND, would almost seem to be an elementary substance; and yet this can hardly be the actual case. The philosophical account of a crystal, as “some substance, all the particles of which, being free to move, have been operated upon in the way of a chemical, perhaps an electrical change,” certainly makes against it; for, according to this definition, such “substance” is a first desideratum, without which we cannot have the “crystal.” Thus, oxygen and hydrogen, blended together in certain definite proportions, yield the fluid substance, WATER; and the “crystal” of water is ICE. In like manner, common white carbonate oflime, and the fluor spars, whose ingredients we know, are in daily process of formation.
The philosophical idea, so accurately expressed in the above definition, is, doubtless, correct, if once we assume a past history for some substance, and take the crystal before us as its result. But, whether all bodies which we now meet with under the form of crystalshave, in point of fact, had such a history, is quite another question.
The diamond is universally held to be pure CARBON crystallized. Its high refraction indicated this to Newton long ago; and the proof has since been given twofold: for the diamond scales off and evaporates under intense heat, and its dust hascarbonizediron-filings, turning them into steel.
Further, this carbon is supposed to be of vegetable origin; and, if so, it would seem to follow that there must have been plants, and perhaps coal-strata, before there could be any diamonds.
Butwhat was the processactually carried out in nature? No one has hitherto succeeded in obtaining this gem, answering to the conditions of a “brilliant” in water, lustre, and weight, by any attempted method,from the base of carbon. The French chemists have now, for some years past, been experimenting uponboron, by means of the voltaic battery; and they have, it seems, taken out of the crucible sundry small, pale crystals, which are found to be nearly as hard as adamantine spar (a variety ofcorundum); but they cannot show, as the fruit of their labours, a diamond weighing one carat, and worth, according to the tariff, eight pounds sterling in the market of Europe. Indeed, if this boron be a mineral intermediate between carbon and silex, their gems will assuredly partake of the character of rock-crystal, a stone which has no affinity with the diamond whatever.
The process of Nature, therefore, being unknown, if indeed it ever took place, the question fairly arises—whether diamond be a derived crystal, or itself an original type of created matter. Or it might be put thus: “If diamond be the purest form of carbon known, what is carbon then but diamond debased?”
Neither does this exhaust the argument. The ruby owns a matrix: the pearl grows in the mother-of-pearl. What is the nature of the diamond-rock? Is it a dark conglomerate? or is it diaphanous?
We know how diamonds are obtained: how they are picked out of the crevices of certain rocks, and washed out of the sands of certain rivers—in the Carnatic, and Brazil, and Borneo; but we do not seem to be much nearer to the history of their parentage.
Again,what istheir “crust” or coating with which they are always found enveloped? Is it an integral part of the stone, or is it adventitious? In the best diamonds this crust is of a greenish hue.
Some say that while the gem itself haspositiveelectricity, its crust showsnegative. If this be so, the last question is answered—the crust in that case cannot be an integral part of the stone. The only absolute reason I know of for concluding the diamond to be aderivedsubstance is, that it is laminar. The Eastern lapidaries, as it is well known, will sometimesdividea stone by striking it a sharp blow in the cleavage.
After all, the most extraordinary property of the diamond, as pure carbon, is its weight. It is fifty times the weight of refined charcoal. How was the element of carbon condensed and inspissated thus? Was it by the action of LIGHT? This is the vegetable analogy; aswe see in the case of all growing plants: did it hold here?
If we were to inquire how oriental sapphires, including the ruby, the blue sapphire, the emerald, and the amethyst, are formed from CLAY, that clay which exists in the granite rocks, the difficulty would be nearly as great. We do not know at all.
But there is some satisfaction in having undoubted proof of the nature of their “base.” And the obvious evidence upon this point is very simple, and prior to that of chemical analysis. My own attention was first drawn to it many years ago, in a casual remark made by a friend. We were handling some crystals of thewhitesapphire, a stone of little value. “These look very like glass,” said I. “Yes, but you may always tell them from glass by theircoldness. Touch one with your tongue.” Then followed the inquiry. “And why is it so much colder than glass is?” “Because the ‘base’ of the sapphire is CLAY, and clay is a very cold substance.”
Let us now pass on to consider the question ofCOLOUR. In the existing varieties of gems, we have all the colours of thespectrumperpetuated and vivid.
What is the source of these colours? And how are they blended with the solid crystal?
There seems to be no reason for doubting that the immediate source or cause of colour is the presence of some oxidized metal. All the colours which Nature has impressed appear, as far as we can trace them, to be due to such a presence. Opaline tints, and those of the “cat’s eye,” are an exception; being the perceptible result of a peculiar texture and configuration; so also are the iridescent hues on asoap-bubble, which are probably caused by polarized light. But it isa metalwhich makes the bark of certain trees and shrubs to glisten; aided, in the case of the birch and wheat-stubble, by particles of silex. It is a metal, absorbed from juices of the soil, which gives their tints to flowers, and their deep tinge to fruits. It is a metal which dyes the plumes of the king-fisher; and the gleaming scales of the dragon-fly and diamond-beetle owe their brilliancy to metallic lustre. Why should this all-pervading law vary in the crystals?
We know that metals proper affect crystalline forms,assuming them spontaneously; and we know that the gems have come in contact with metals.Iron, whose rust is of a reddish hue, enters into many of them; and in theredstones it is said to be abundant.
Probably, the finer permanent tints are due togold, in infinitesimal proportions. Professor Faraday has said that the ruby-tinted glass called “Bohemian” derives its colour from gold in a pure form, finely attenuated, and not from any chemical combination of that substance.
A white diamond has far more lustre than one which is yellow or violet-tinted. But in all the sapphires, the deeper the hue, the more brilliant and valuable the stone. Hence the technical term for the colour of a diamond is itswater. In all these gems the hues (whatever their origin) are homogeneously united with the crystal; and themodus operandiof Nature is a profound secret.
When we descend in the mineralogical scale, and come to such stones as agates and jaspers, the process which has been followed seems quite capable of being traced—for its antiquity is not so great. The colours which we now find in pebbles more or less opaque, though occasionallylively, exist under very different conditions from those by which they reside in the crystalline gems. It is necessary, however, to consider first, the origin and nature ofpebblesas distinguished from casual fragments of stone.
This was long held to be one of Nature’s riddles; but as soon as it was experimentally dealt with, it met with a solution in some of its most difficult points.
It was early decided that pebbles aredistinct formations, complete in themselves, except in so far as they have been worn away by gradual attrition. The first difficulty was, how to account for the great hardness of many of our seaside specimens. Although for the most part inclosing an “organism,” which must have been that of some zoophyte, they show no traces, in their present compact texture, of the soft and yielding consistency they must at that time have possessed. The matrix in which they lie, and from which they drop as the ripe nuts fall from a hazel-bush, is seldom or never of so hard a substance as are the pebbles themselves; in many cases the difference is as great as between the teeth and gums of a living mammal.
But the evidence of the inclosed organism is conclusiveas to a past history; and in all mixed pebbles—and ninety-nine out of a hundred of ours are mixed—it is quite certain that animpregnation, or an actualinfiltration, has taken place.
Either a fluid menstruum, usually siliceous, must have enveloped and saturated the animal form, or there was actual injection of chalcedony and limestone, in a soft state, into the tubes and cells of the skeleton first, and afterwards into the pores and crevices of the new stone. Frequently both processes have obtained. The only alternative, viz. that which suggests that composite pebbles, revealing in their structure distinct traces of animal or vegetable organization,may have beenformed thus at first, like the coloured prints in a book, I consider to be untenable. One might as readily credit a spontaneous growth of almond-cakes or oyster-patties by some sudden spasmodic effort of our present sea and land.
Impregnation has, no doubt, been always going on.
A Frenchsavant, M. Reaumur, above a century ago, wrote as follows:—“By a coarse operation emery is reduced to powder and suspended in water for several days; but nature may go much further than this, for the particles which water detaches from hard stones, by simpleattrition, are of an almost inconceivable degree of fineness. Water thus impregnated contributes to the formation of pebbles by petrifying the stone, as it were, a second time. Stones already formed, but having as yet a spongy texture, acquire a flinty hardness by impregnation with this crystalline fluid.”[3]
From such a source, as he supposes, has arisen the close texture of Egyptian pebbles, coloured jaspers, and even agates. If he means to include thehomogeneousagates, which are alike free from sparry crystals, metallic scum, and all traces of organized matter, I do not agree with him. But in the case ofmixedchalcedonic pebbles, among which may be classed our pretty Isle of Wight specimens, no doubt such impregnation took place, and was followed by a further process of infiltration. For when the flint-nodules,impregnatedas above, were still soft—soft enough we know they were to take delicate impressions of the spines of the echinus—chalcedony, in a semi-fluid or viscous state, would pass through the pores of the flint, because the former is the finer substance of the two. And after such infiltration, the entire lumpwould harden, resisting, for the most part, further change. And this would be the pebble as we now find it.
In the “Geological Museum,” now open in Jermyn Street, there is a case (on the first floor) where the nature of infiltration is well shown in some jasper-agates. It will readily be seen here that each internal layer has been formed in successionfrom without, the centre of the pebble filling up last. In another case (labelled “Silica”), on the opposite side of this room, are some “choanites” and “sponges” presented by the author.
Those latter will be found worthy of ten minutes’ inspection, even as seen through the plate of glass which serves to protect them. They are selected, not as being the finest specimens in his cabinet, but as illustrating, each of them, a particular animal, or a peculiarpositionof one in the fossil state. They are, however, very good specimens, much above the average; and if any one became missing, it could never be exactly replaced, though you should search the world over. Nature does not stamp the same “medal”twice. Any person who, after examining these, likes to start a theory of his own to account for their forms and colours, has my full permission to do so. But one word I would say infriendly warning, seeing that theories do abound. The Chinese, that ancient and wise people, have a theory that “asbestos” cloth may have been manufactured “of the hair of certain rats that lived in the flames of certain volcanoes.” It were monstrous to doubt it.
In my beach-rambles I have often picked up and examined globes of sandstone which were partially chalcedonized, and that by evident infiltration. The lapidaries call these “sand-agates,” and reject them as unfit for the wheel; and so they are at present, but it would be instructive to meet with some of them twenty years hence, after they had undergone a more confirmed treatment at the hands of Dame Nature.
The well-known specimens of “petrified wood,” common on our coasts, and occurring in some beautiful varieties of beech and acacia in the bays of South Devon, are a further example of infiltration; but the process here must have been somewhat different.
The presence of metallic particles, what lapidaries term the “moss,” in many of our agates, argues an impregnating fluid, thoroughly charged with mineral matter. In most cases this fluid was a ferruginous stream, such as may often be seen issuing from some hidden reservoir,and trickling down the face of a cliff of gault or greensand. This tinges everything that lies in its path with an indelible red stain; it then oozes on through the shingle, and reaches the verge of the sand. The nearest pool becomes saturated between tides, and the suspended crystals of salt, which are of a penetrating character (as the state of your beaching-boots will soon inform you), enter into chemical combination with the metallic rust, and help to conduct its particles into the heart of many a limestone pebble.
Dark inland pebbles, on the other hand, will discharge much of the oxide which they have imbibed, and may be observed to brighten and improve their complexions after a few months’ sponging and tossing in the purer sea-water.
Some of our handsomer pebbles, when cut in two, reveal blotches of metal, which are glossy after polishing on the wheel. This metal is occasionally native iron. The darker varieties of “moss” contain a good deal of manganese, and some silver.
From what has been said about impregnation, we may readily conclude that thecoloursfound in our agate-pebbles have been chemically inwrought, and that thesymmetricalpatterns, over which these colours are disposed, are not due to a succession of “layers,” as in the ribbon-jaspers and Scotch pebbles, but must be referred to the organization of some extinct zoophyte, whose skeleton is preserved in the existing fossil.
The cause of translucency, or eventransparency, in some pebbles is, no doubt, to be sought in their finer and more even texture, but especially in the latter quality. Sir Isaac Newton was of opinion that the opacity of certain substances is simply a result of their cross-grained composition. He held that in a transparent body the particles must be regularly and evenly disposed at equal intervals, so that a ray of light entering such a substance would pass steadily on, according to the known laws of gravity and motion, meeting with no obstruction beyond that of the homogeneous density of the medium which it had to traverse. Whereas, in opaque bodies, he supposes these constituent particles to be unevenly disposed, and that the ray which enters at the surface is, as it were, pushed about and thrust aside, and at length lost to sight.
The purity of spring-water, when undisturbed, illustrates this beautiful theory of the great philosopher; and,among solid substances, good glass, especially plate-glass which, after fusing in the furnace, has been carefully run and settled in the frames. It may also be simply shown in the act of wetting or steeping certain dry substances. Thus, stout writing-paper, owing to its cross texture, is opaque when dry; but if we immerse a sheet of it in oil, and then hold it up to the light, we find it has become transparent. For the smooth medium thus imbibed has entered its pores, andequalizedthe general texture.
We find also a striking argument for the probable truth of Newton’s eagle-eyed conclusion in certain minerals which possess double refraction.
ICELAND SPAR, one of these, is perhaps the most perfectly transparent solid with which we are acquainted. Now, Iceland Spartransmitsboth the rays, as we see in the twofold image which is presented to us. But TOURMALINE is opaque, even the red specimens looking almost black; and we find that Tourmalineabsorbsone of the two rays of polarized light. This singular stone polarizes a beam of light if it enter in any direction but that of the longer axis.
No solid with which we are acquainted is absolutely transparent. And there is no perfectreflectorknown.The best-polished surfaceabsorbs nearly one-halfof that quantity of light which strikes upon it.
As to our seaside pebbles, the most compact of them are evenvisiblyporous. Cut through the hardest jasper, and polish one face till it shines like a steel mirror, and then hold it so as to reflect the light, you will at once discern numerous minute specks or flaws on this surface, as if the point of a needle or graving-tool had been busily at work upon it. These specks have always been there. They areair-holes, and in the case of a fossil-pebble were, some of them, doubtless, connected with the position which the animal occupied just before he died. These air-holes must have traversed this hard stone in every direction, for, cut the pebble how you will, you meet with them. Others again, incomparably more numerous, but which can scarcely be discerned without the aid of a powerful microscope, are the trueporesbelonging to this apparently impenetrable substance.
I have found that the action of daylight tells even upon polished agates after a time. Some of the spots and markings in the finest stones grow fainter in the course of many years. Others appear to deepen. This is, no doubt, a change resulting from the oxygen, containedin a beam of light, acting readily upon carbon, silex, and other substances. And it furnishes an independent argument for concluding that the visible beauty of these formations, in perpetuating a coloured pattern, has been due rather to mixedchemicalprocesses than to pure crystallography.
The fossil nodules, mostly siliceous, which we find upon a sea-beach, areintegralspecimens. It never but once happened to me to meet with what appeared to betwochoanites in the same pebble, and I incline now to believe that this was in factonechoanite who haddividedhimself after the manner of the Luidia. But even supposing that here were, indeed, a pair of perfect animals, when it is considered that this was one single instance, occurring among more than a thousand picked up by me, in which the choanites were always solitary, such an exception may be almost said to prove the rule.
The late lamented Hugh Miller has stated the like fact concerning his Morayshire and Cromarty icthyolites. At pp. 194, 195, of his “Cruise of the Betsy,” he remarks that “the limestone nodules take very generally theformof the fish which they inclose; they are stone coffins carefully moulded to express the outline ofthe corpses lying within.” Then, after observing that the shape of the stone conforms to the attitude of the fish in every instance, he goes on to state that “thesizeof the fish regulates that of the nodule. The coffin is generally as good a fit in size as in form; and the bulk of the nodule bears almost always a definite proportion to the amount of animal round which it had formed.”
He then gives, in his usual clear and graphic language, the following remarkable statement, the result of direct experiment.
“When a calcareous earth, mixed up with sand, clay, and other extraneous matters, was deposited on some of the commoner molluscs of our shores, it was universally found that the mass, incoherent everywhere else, had acquired a solidity wherever it had been penetrated by the animal matter of the molluscs. Each animal, in proportion to its size, was found to retain, as in the fossiliferous spindles of the Old Red Sandstone, its coherent nodule around it. Here the animal matter gave solidity to the lime in contact with it. But in thenaturalphenomenon of the icthyolite beds, there was yet a further point, for in these the animal matter must have possessed suchan affinityfor the mineral, as to form, in an argillaceouscompound, a centre of attraction powerful enough to draw together the lime diffused throughout the mass.”
Hugh Miller concludes the above passage by saying that “it still remains for the geologic chemist to discover on what principle masses of animal matter should form the attracting nuclei of limestone nodules.”
Upon which last remark, I would suggest that the principle of the “law of definite proportions,” established by Dalton, and fully borne out by all succeeding experiments in chemistry, appears to meet the case, geologically as well as chemically, in every respect. For such a law must of course obtain, whether the chemical ingredients be present in the forms of mineral, vegetable, or animal life; in fact, we have never known the law to vary. It holds for the compounded elements which we term AIR and WATER; it holds for the crystals; it holds for vascular and cellular tissues; why should it fail when the further instance of a mollusc or a zoophyte is in question?
I see no reason to doubt that the blood, muscle, membrane, or adipose matter of any animal have their due respective affinities for the different substances of the mineral creation.
No doubt, however, electricity, as an active cause, bears directly upon all such phenomena.
I remember many years since being greatly perplexed with thediscovery(as I then thought it) that in certain parts of the Isle of Wight, and along the Dorsetshire coast, the rows of dark flints imbedded in the upper chalk of the cliff-ranges were allbroken; brokensmall, so that if one were taken out of its chalk socket it crumbled in your hand. Often and often, I turned this fact over in my mind, and sought some apparent way to account for it. But I think I now see one way to account for it; and which may perhaps be judged worthy of acceptance, until a better solution is hit upon. In Dr. Hook’s experiment with that once common household implement, the “flint and steel,” he found that thesparkswhich “fly” upon collision taking place are minute spherules of metal. And further, that this metal was now notsteelany longer, but iron; the fragments struck offhaving lost their polarityin the moment of contact with the flint.
This experiment shows that silex possesses some remarkable affinity for the magnetic fluid, since in this case it had robbed the steel of it, for those spheruleswould not answer to the magnet. May not, therefore, the rows of flints in the cliff have attracted the lightning in severe thunderstorms, and been shivered by the blow? This would not necessarily hurl the chalk down.
The Arabs have a proverb which says, “Under the lamp it is dark.” Certainly, the chief mystery of every animated creature seems to residein its life, andLifeis like a burning lamp. Once the life extinct, we can anatomize and analyze, and arrive at many partial conclusions; but, meanwhile, the life has departed, and we do not know what that was. The nearest thing to its likeness isexpression; and animals rank high in the scale of being, according as they command and impart expression. A dog or horse have a great deal; a bird some; a reptile or insect, absolutely none to our eyes.
With these latter, however, theirhabits, while alive, take the place of any more intelligent expression; especially some of their more excited movements. We know by thesound, when a snake is angry; and as to motion, the attack of a provoked hornet is a startling thing to witness. Ordinarily speaking, however, all their habits tend to concealment; no doubt, for the sake of safety. I believeno one ever sees the Sphynx-moth, called a “Death’s-head” (Acherontia Atropos), on the wing. Yet we discern many others which, like it, fly in the hours of dusk. But this insect whirls through the air like a stone from a sling. It has never yet, in my experience as a naturalist, been my lot to meet with the burrowing insect called an Ant-lion. Only twice in my life have I encountered a slow-worm in the woods of Devon and the Isle of Wight. And to instance the case of a far commoner creature, how seldom does it happen to any one to take the large dragon-fly behind his green leaf!
And yet the problems of inanimate matter are perhaps the most difficult to solve. They have deeply exercised philosophers in every age of the world.
“All things considered,” says Newton, “I think it probable that God, in the beginning, formed matter in solid, hard, impenetrable, movable particles; of such sizes and figures, and with such other properties as most conduced to the end for which He formed them. And that these primitive particles, being solids, are incomparably harder than any of the sensible porous bodiescompounded of them; even so hard as never to wear, or break in pieces; no other power being able to divide what God made one in the first Creation. While these corpuscles remain entire, they may compose bodies of one and the same matter and texture in all ages; but should they wear away or break in pieces, the nature of things depending on them would be changed. Water and earth composed of old worn particles and fragments of particles, would not be of the same nature and texture now with water and earth composed of entire particles at the beginning. And therefore, that Nature may be lasting, the changes of corporeal things are to be placed only in the various separations and new associations of these permanent corpuscles.”
So wrote the man, “Qui genus humanum ingenio superavit,” who at the age of twenty-four had already invented the Fluxional Calculus, discovered the Decomposition of Light, and enunciated and proved, in a series of lemmas, the law of Universal Gravitation.
But soft! What is this which steals upon our senses through bobbing apple-blossoms at the open casement?It is the delicious, oystery smell of the Sea, as the afternoon tide runs in with a sound like that of fairy-bells upon the sand and rock and loose shingle.
That scent, and sight, and sound, are altogether irresistible. We throw aside Dr. Buckland and Hugh Miller, clap on a “wide-awake,” rush down at once by the zig-zag path, and madly catch up a bunch of dripping tangle, and kick a hole in the moist sand, and presently find that our “Balmorals” are ancle-deep in the brine of a nimble wave.
And now I descry a faint purplish hue upon the red beach which lies at the foot of Culver. To-morrow, we will breakfast early, and hunt up a score of pebbles before the day grows hot.