those alpine strata. But then it is also necessary to include in this character a general hardness and solidity in those vertical strata, otherwise they would not have been properly alpine, or have resisted the wearing and washing powers of the globe, so as to have remained higher than the others; for, the vertical position, or great inclination of those strata, should rather have disposed them the more to dissolution and decay. Let us now see how far we shall be justified in that general conclusion, by the examination of those bodies.
The fact is certain, that those alpine bodies are much harder, or less subject to dissolution and decay, than the horizontal strata. But this must be taken in the general, and will by no means apply to particular cases which might be compared. Nothing, for example, more solid than the lime-stones, or marbles, and iron-stones; nothing more hard or solid than the chirt or flint; and all these are found among the horizontal strata. But, while some strata among those horizontal beds are thus perfectly solid, others are found with so slight degrees of consolidation, that we should not be able to ascribe it to the proper cause, without that gradation of the effect, which leads us to impute the slightest degree of consolidation to the same operations that have produced the complete solidity. While, therefore, the most perfect solidity is found in certain strata, or occasionally among the horizontal bodies, this forms no part of their character in general, or cannot be considered as a distinctive mark, as it truly is with regard to the alpine strata. These last have a general character of consolidation and indissolubility, which is in a manner universal. We are, therefore, now to inquire into the cause of this distinction, and to form some hypothesis that may be tried by the actual state of things, in being compared with natural appearances.
As the general cause of consolidation among mineral bodies, formed originally of loose materials, has been found to consist in certain degrees of fusion or cementation of those materials by means of heat; and as, in the examination of the horizontal strata we actually find very different degrees of consolidation in the several strata, independent of their positions in relation to height or depth, we have reason to believe that the heat, or consolidating operation, has not been equally employed in relation to them all.
We are not now inquiring how an inferior stratum should have been heated in a lesser degree, or not consolidated, while a superior stratum had been consolidated in the most perfect manner; we are to reason upon a fact, which is, that the horizontal strata in general appear not to have been equally or universally consolidated; and this we must attribute to an insufficient exertion of the consolidating cause. But, so far as the erecting cause is considered as the same with that by which the elevated bodies were consolidated, and so far as the vertical situation is a proof of the great exertion of that subterraneous power, the strata which are most erected, should in general be found most consolidated.
Nothing more certain than that there have been several repeated operations of the mineralising power exerted upon the strata in particular places; and all those mineral operations tend to consolidation: Therefore, the more the operations have been repeated in any place, the more we should find the strata consolidated, or changed from their natural state. Vertical strata have every appearance from whence we should be led to conclude, that much of the mineral power had been exerted upon them, in changing their original constitution or appearance. But the question now to be considered is this, How far it may appear that these masses of matter, which now seem to be so different from the ordinary strata of the globe, had been twice subjected to the mineral operations, in having been first consolidated and erected into the place of land, and afterwards sunk below the bottom of the sea, in order a second time to undergo the process of subterraneous heat, and again be elevated into the place where they now are found.
It must be evident, here is a question that may not be easy to decide. It is not to the degree of any change to which bodies may be subject, that we are to appeal, in order to clear up the point in question, but to a regular course of operations, which must appear to have been successively transacted, and by which the different circumstances or situations of those masses are to be discovered in their present state. Now, though it does not concern the present theory that this question be decided, as it is nothing but a repetition of the same operations that we look for; nevertheless, it would be an interesting fact in the natural history of this earth; and it would add great lustre to a theory by which so great, so many operations were to be explained. I am far from being sanguine in my expectations of giving all the satisfaction in relation to this subject that I could wish; but it will be proper to state what I have lately learned with regard to so curious a question, that others, who shall have the opportunity, may be led to inquire, and that thus the natural history of the earth may be enlarged, by a proper investigation of its mineral operations.
With this view I have often considered our schistus mountains, both in the north and south; but I never found any satisfactory appearance from whence conclusions could be formed, whether for the question or against it. The places I examined were those between the alpine countries and the horizontal strata; here, indeed, I have frequently found a confused mass, formed of the fragments of those alpine strata mixed with the materials of the horizontal bodies; but not having seen the proper shape and connection of those several deposits, I always suspended my judgment with regard to the particular operations which might have been employed in producing those appearances.
I had long looked for the immediate junction of the secondary or low country strata with the alpine schistus, without finding it; the first place in which I observed it was at the north end of the island of Arran, at the mouth of Loch Ranza; it was upon the shore, where the inclined strata appeared bare, being; washed by the sea. It was but a very small part that I could see; but what appeared was most distinct. Here the schistus and the sandstone strata both rise inclined at an angle of about 45 deg.; but these primary and secondary strata were inclined in almost opposite directions; and thus they met together like the two sides of a _lambda_, or the rigging of a house, being a little in disorder at the angle of their junction. From this situation of those two different masses of strata, it is evidently impossible that either of them could have been formed originally in that position; therefore, I could not here learn in what state the schistus strata had been in when those of the sand-stone, &c, had been superinduced.
Such was the state of my mind, in relation to that subject:, when at Jedburgh upon a visit to a friend, after I had returned from Arran, and wrote the history of that journey; I there considered myself as among the horizontal strata which had first appeared after passing the Tweed, and before arriving at the Tiviot. The strata there, as in Berwickshire, which is their continuation to the east, are remarkably horizontal for Scotland; and they consist of alternated beds of sand-stone and marl, or argillaceous and micaceous strata. These horizontal strata are traversed in places with small veins of whin-stone, as well as greater masses forming rocks and hills of that material; but, except it be these, (of which there are some curious examples), I thought there could be nothing more of an interesting nature to observe. Chance, however, discovered to me what I could not have expected or foreseen.
The river Tweed, below Melrose, discovers in its bed the vertical strata of the schistus mountains, and though here these indurated bodies are not veined with quartz as in many places of the mountains, I did not hesitate to consider them as the same species, that is to say, the marly materials indurated and consolidated in those operations by which they had been so much changed in their place and natural position. Afterwards in travelling south, and seeing the horizontal softer strata, I concluded that I had got out of the alpine country, and supposed that no more of the vertical strata were to be observed.
The river Tiviot has made a wide valley as might have been expected, in running over thole horizontal strata of marly or decaying substances; and the banks of this river declining gradually are covered with gravel and soil, and show little of the solid strata of the country. This, however, is not the case with the Jed, which is to the southward of the Tiviot; that river, in many places, runs upon the horizontal strata, and undermines steep banks, which falling shows high and beautiful sections of the regular horizontal strata. The little rivulets also which fall into the Jed have hollowed out deep gullies in the land, and show the uniformity of the horizontal strata.
In this manner I was disposed to look for nothing more than what I had seen among those mineral bodies, when one day, walking in the beautiful valley above the town of Jedburgh, I was surprised with the appearance of vertical strata in the bed of the river, where I was certain that the banks were composed of horizontal strata. I was soon satisfied with regard to this phenomenon, and rejoiced at my good fortune in stumbling upon an object so interesting to the natural history of the earth, and which I had been long looking for in vain.
Here the vertical strata, similar to those that are in the bed of the Tweed, appear; and above those vertical strata, are placed the horizontal beds, which extend along the whole country.
The question which we would wish to have solved is this; if the vertical strata had been broken and erected under the superincumbent horizontal strata; or if, after the vertical strata had been broken and erected, the horizontal strata had been deposited upon the vertical strata, then forming the bottom of the sea. That strata, which are regular and horizontal in one place, should be found bended, broken, or disordered at another, is not uncommon; it is always found more or less in all our horizontal strata. Now, to what length this disordering operation might have been carried, among strata under others, without disturbing the order and continuity of those above, may perhaps be difficult to determine; but here, in this present case, is the greatest disturbance of the under strata, and a very great regularity among those above. Here at least is the most difficult case of this kind to conceive, if we are to suppose that the upper strata had been deposited before those below had been broken and erected.
Let us now suppose that the under strata had been disordered at the bottom of the sea, before the superincumbent bodies were deposited; it is not to be well conceived, that the vertical strata should in that case appear to be cut off abruptly, and present their regular edges immediately under the uniformly deposited substances above. But, in the case now under consideration, there appears the most uniform section of the vertical strata, their ends go up regularly to the horizontal deposited bodies. Now, in whatever state the vertical strata had been in at the time of this event, we can hardly suppose that they could have been so perfectly cut off, without any relict being left to trace that operation. It is much more probable to suppose, that the sea had washed away the relics of the broken and disordered strata, before those that are now superincumbent had been begun to be deposited. But we cannot suppose two such contrary operations in the same place, as that of carrying away the relics of those broken strata, and the depositing of sand and subtile earth in such a regular order. We are therefore led to conclude, that the bottom of the sea, or surface of those erected strata, had been in very different situations at those two periods, when the relics of the disordered strata had been carried away, and when the new materials had been deposited.
If this shall be admitted as a just view of the subject, it will be fair to suppose, that the disordered strata had been raised more or less above the surface of the ocean; that, by the effects of either rivers, winds, or tides, the surface of the vertical strata had been washed bare; and that this surface had been afterwards sunk below the influence of those destructive operations, and thus placed in a situation proper for the opposite effect, the accumulation of matter prepared and put in motion by the destroying causes.
I will not pretend to say that this has all the evidence that should be required, in order to constitute a physical truth, or principle from whence we were to reason farther in our theory; but, as a simple fact, there is more probability for the thing having happened in that manner than in any other; and perhaps this is all that may be attained, though not all that were to be wished on the occasion. Let us now see how far any confirmation may be obtained from the examination of all the attending circumstances in those operations.
I have already mentioned, that I had long observed great masses of _debris_, or an extremely coarse species of pudding-stone, situated on the south as well as north sides of those schistus mountains, where the alpine strata terminate in our view, and where I had been looking for the connection of those with the softer strata of the low country. It has surely been such appearances as these which have often led naturalists to see the formation of secondary and tertiary strata formed by the simple congestion of _debris_ from the mountains, and to suppose those masses consolidated by the operation of that very element by which they had been torn off from one place and deposited in another. I never before had data from whence to reason with regard to the natural history of those masses of gravel and sand which always appeared to me in an irregular shape, and not attended with such circumstances as might give light into their natural history; but now I have found what I think sufficient to explain those obscure appearances, and which at the same time will in some respect illustrate or confirm the conjecture which has now been formed with regard to the operations of the globe in those regions.
In describing the vertical and horizontal strata of the Jed, no mention has been made of a certain pudding-stone, which is interposed between the two, lying immediately upon the one and under the other. This puddingstone corresponds entirely to that which I had found along the skirt of the schistus mountains upon the south side, in different places, almost from one end to the other. It is a confused mass of stones, gravel, and sand, with red marly earth; these are consolidated or cemented in a considerable degree, and thus form a stratum extremely unlike any thing which is to be found either above or below.
When we examine the stones and gravel of which it is composed, these appear to have belonged to the vertical strata or schistus mountains. They are in general the hard and solid parts of those indurated strata, worn and rounded by attrition; particularly sand or marl-stone consolidated and veined with quartz, and many fragments of quartz, all rounded by attrition. In this pudding-stone of the Jed, I find also rounded lumps of porphyry, but have not perceived any of granite.[32] This however is not the case in the pudding-stone of the schistus mountains, for, where there is granite in the neighbourhood, there is also granite in the pudding-stone.
[Note 32: A view of this object is seen in plate 3d. It is from a drawing taken by Mr Clerk of Eldin.]
From this it will appear, that the schistus mountains or the vertical strata of indurated bodies had been formed, and had been wasted and worn in the natural operations of the globe, before the horizontal strata were begun to be deposited in those places; the gravel formed of those indurated broken bodies worn round by attrition evince that fact. But it also appears that the mineral operations of the globe, melting and consolidating bodies, had been exerted upon those deposited strata above the vertical bodies.
This appears evidently from the examination of our pudding-stone. The vertical strata under it are much broken and injected with ferruginous spar; and this same spar has greatly penetrated the pudding-stone above, in which are found the various mineral appearances of that spar and iron ore.
But those injecting operations reach no farther up among the marl strata in this place; and then would appear to have been confined to the pudding-stone. But in another place, about half a mile farther up the river, where a very deep section of the strata is discovered, there are two injections from below; the one is a thin vein of whin-stone or basaltes, full of round particles of steatites impregnated with copper; it is but a few inches wide, and proceeds in a kind of zigzag. The other appears to have been calcareous spar, but the greatest part of it is now dissolved out. The strata here descend to the bottom of the river, which is above the place of the pudding-stone and vertical strata. Neither are these last discoverable below the town of Jedburgh, at least so far as I have seen; and the line of division, or plane of junction of the vertical and horizontal strata, appears to decline more than the bed of the river.
But it may be asked, how the horizontal strata above, among which are many very strong beds, have been consolidated. The answer to this question is plain. Those strata have been indurated or consolidated in no other manner than the general strata of the earth; these being actually the common strata of the globe; while the vertical or schistus strata are the ordinary strata still farther manufactured, (if we may be allowed the expression) in the vicissitude of things, and by the mineral operations of the globe. That those operations have been performed by subterraneous heat has been already proved; but I would now mention some particular appearances which are common or general to those strata, and which can only be explained upon that principle.
The red marly earth is prevalent among those strata; and it is with this red ferruginous substance that many of the sand-stone strata are tinged. It is plain that there had been an uniform, deposits of that sand and tinging earth; and that, however different matter might be successively deposited, yet that each individual stratum should be nearly of the same colour or appearance, so far as it had been formed uniformly of the same subsiding matter. But, in the most uniform strata of red sand-stone, the fracture of the stone presents us with circular spots of a white or bluish colour; those little spheres are in all respects the same with the rest of the stone, they only want the tinging matter; and now it may be inquired how this has come about.
To say that sphericles of white sand should have been formed by subsiding along with the red sand and earth which composed the uniform stratum whether of sand-stone or marl, (for it happens equally in both,) is plainly impossible, according to our notion of that operation in which there is nothing mysterious. Those foliated strata, which are of the most uniform nature, must have been gradually accumulated from the subsiding sand and earth; and the white or colourless places must have had their colour destroyed in the subsequent cementing operations. It is often apparent, that the discharging operation had proceeded from a centre, as some small matter may be perceived in that place. I know not what species of substance this has been, whether saline or phlogistic, but it must have had the power of either volatilising or changing the ferruginous or red tinging substance so as to make it lose its colour.
I have only mentioned spherical spots for distinctness sake; but this discharging operation is found diversifying those strata in various ways, but always referable to the same or similar causes. Thus, in many of the veins or natural cracks of those strata, we find the colour discharged for a certain space within the strata; and we often see several of those spots united, each of them having proceeded from its own centre, and uniting where they approached. In the two veins above mentioned, of whin-stone and spar traversing the strata, the colour of the strata is, discharged more or less in the places contiguous with the veins.
I am now to mention another appearance of a different kind. Those strata of marl are in general not much consolidated; but among, them there are sometimes found thin calcareous strata extremely consolidated, consequently much divided by veins. It is in the solid parts of those strata, perfectly disconnected from the veins, that there are frequent cavities curiously lined with crystals of different sorts, generally calcareous, sometimes containing also those that are siliceous, and often accompanied with pyrites. I am persuaded that the origin of those cavities may have been some hollow shells, such as _echini_ or some marine object; but that calcareous body has been so changed, that it is not now distinguishable; therefore, at present, I hold this opinion only as conjecture.
Having, in my return to Edinburgh, traveled up the Tiviot, with a view to investigate this subject of primary and secondary operations of the earth, I found the vertical strata, or alpine schistus, in the bed of the river about two miles below Hawick. This was the third time I had seen those vertical bodies after leaving the mountains of Lauderdale. The first place was the bed of the river Tweed, at the new bridge below Melrose; but here no other covering is to be seen above those vertical strata besides the soil or traveled earth which conceals every thing except the rock in the bed of the river. The second place was Jedburgh, where I found the vertical strata covered with the horizontal sandstone and marl, as has been now described. The third place was the Tiviot, and this is that which now remains to be considered.
Seeing the vertical strata in the bed of the river, I was desirous to know if those were immediately covered with the horizontal strata. This could not be discovered in the bed of the river where the rock was covered upon the banks with travelled earth. I therefore left the river, and followed the course of a brook which comes from the south side. I had not gone far up the bank, or former boundary of the Tiviot, when I had the satisfaction to find the vertical strata covered with the pudding-stone and marly beds as in the valley of the Jed.
It will now be reasonable to suppose that all the schistus which we perceive, whether in the mountains or in the valleys, exposed to our view had been once covered with those horizontal strata which are observed in Berwickshire and Tiviotdale; and that, below all those horizontal strata in the level country, there is at present a body or basis of vertical or inclined schistus, on which the horizontal strata of a secondary order had been deposited. This is the conclusion that I had formed at Jedburgh, before I had seen the confirmation of it in the Tiviot; it is the only one that can be formed according to this view of things; and it must remain in the present state until more evidence be found by which the probability may be either increased or diminished.
Since writing this, I have read, in the Esprit de Journaux, an abstract of a memoir of M. Voigt, upon the same subject, which I shall now transcribe.
“La mer a commence par miner les montagnes primitives dont les debris se sont precipites au fond. Ces debris forment la premiere couche qui est posee immediatement sur les montagnes primitives. D’apres l’ancien langage de mineurs, nous avons jusqu’aujourd’hui appelle cette couche _le sol mort rouge_, parce qu’il y a beaucoup de rouge dans son melange, qu’elle forme le sol ou la base d’autres couches, et peut-etre de toutes, qu’elle est entierement inutile et, en quelque facon, morte pour l’exploitation des mines. Plusieurs se sont efforces de lui donner un nom harmonieux; mais ils ne l’ont pu sans occasionner des equivoques. Les mots _Breche Puddinstone Conglomerations_, &_c_. designent toujours des substances autres que cette espece de pierre.
“Il est tres agreable de l’examiner dans les endroits ou elle forme des montagnes entieres. Cette couche est composee d’une quantite prodigieuse de pierres arrondies, agglutinees ensemble par une substance argileuse rouge et meme grise, et le toute a acquis assez de durete. On ne trouve dans sa composition aucune espece de pierre qui, a en juger par les meilleures observations, puisse avoir ete formee plus tard qu’elle; on n’y voit par-tout que des parties et des produit des montagnes primitives principalement de celles qui abondent le plus dans ces contrees. Le sol mort, par exemple, qui compose les montagnes des environs de Walbourg, pres d’Eisenach, contient une quantite de gros morceaux de granit et de schiste micace; c’est vraisemblablement parce que les montagnes primitives les plus voisines de Rhula, etc. sont, pour la plus part, formees de ces deux especes de pierres. Pres de Goldlauter, le sol mort consiste presque tout en porphyre, substance dont sont formees les montagnes primitives qui y dominent; et le Kiffauserberg dans la Thuringe a probablement recu ces morceaux arrondis de schiste argileux des montagnes voisine du Hartz. Vous trouverez ici que le schiste argileux existoit deja lorsque la mer a jette les premiers fondemens de nos montagnes stratifiees. Je serois fort etonne que quelqu’un me montrat un sol mort qui contint un morceaux de gypse, de marne, de pierre puante et autres. Quoiqu’il en soit il n’est pas aise d’expliquer pourquoi on ne trouve point de corps marins petrifies dans cette espece de pierre. C’est peut-etre que, par l’immense quantite de pierres dures roulees dans le fond de la mer, ils ont ete brises avant qu’ils aient commence de s’agglutiner ensemble. Mais on rencontre sur-tout au Kiffhauserberg des troncs d’arbres entiers petrifies; preuve qu’il y avoit deja ou de la vegetation avant que l’ocean destructeur se fut empare de ces cantons, ou du moins que quelques isles avoient existe au-dessus de la surface.”
Here we find the same observations in the mountains of Germany that I have been making with regard to those of Scotland. I have formerly observed masses of the same kind in the west of England, to the east of the Severn; but I could not discover any proper connection of that mass with the regular strata. I have also long observed it in many parts of Scotland, without being able to attain a sufficiently satisfactory idea with regard to those particulars by which the alternation of land and water, of the superficial and internal mineral operations of the globe, might be investigated.
It will be very remarkable if similar appearances are always found upon the junction of the alpine with the level countries. Such an appearance, I am inclined to think, may be found in the Val d’Aoste, near Yvree. M. de Saussure describes such a stone as having been employed in building the triumphal arch erected in honour of Augustus. “Cet arc qui etoit anciennement revetu de marbre, est construit de grands quartiers d’une espece assez singuliere de poudingue ou de gres a gros grains. C’est une assemblage de fragmens, presque touts angulaires, de toutes sortes de roches primitives feuilletees, quartzeuses, micacees; les plus gros de ces fragmens n’atteignent pas le volume, d’une noisette. La plupart des edifices antiques de la cite l’Aoste et de ses environs, sont construits de cette matiere; et les gens du pays sont persuades que c’est une composition; mais j’en ai trouve des rochers en place dans les montagnes au nord et au-dessus de la route d’Yvree.”
We may now come to this general conclusion, that, in this example of horizontal and posterior strata placed upon the vertical _schisti_ which are prior in relation to the former, we obtain a further view into the natural history of this earth, more than what appears in the simple succession of one stratum above another. We know, in general, that all the solid parts of this earth, which come to our view, have either been formed originally by subsidence at the bottom of the sea, or been transfused in a melted state from the mineral regions among those solid bodies; but here we further learn, that the indurated and erected strata, after being broken and washed by the moving waters, had again been sunk below the sea, and had served as a bottom or basis on which to form a new structure of strata; and also, that those new or posterior strata had been indurated or cemented by the consolidating operations of the mineral region, and elevated from the bottom of the sea into the place of land, or considerably above the general surface of the waters. It is thus that we may investigate particular operations in the general progress of nature, which has for object to renovate the surface of the earth necessarily wasted in the operation of a world sustaining plants and animals.
It is necessary to compare together every thing of this kind which occurs; it is first necessary to ascertain the fact of their being a prior and posterior formation of strata, with the mineral operations for consolidating those bodies formed by collection of the moveable materials; and, secondly, it is interesting to acquire all the data we can in order to form a distinct judgment of that progress of nature in which the solid body of our land is alternately removed from the bottom of the sea into the atmosphere, and sunk again at the bottom of the sea.
I shall now transcribe what M. Schreiber has wrote in relation to this subject. It is in a memoir concerning the gold mine of Gardette, published in the Journal de Physique.
“Avant de quitter la montagne de la Gardette qu’il me soit permis de rapporter une observation qui peut-etre n’est pas denuee de tout interet pour les naturalistes; je l’ai faite dans une galerie a environ cinquante-trois toises a l’ouest du principal puit laquelle a ete poussee sur la ligne de reunion de la pierre calcaire, et du granit feuillete ou gneiss pour fonder le filon dans cet endroit. Ce filon a six pouces d’epaisseur, et consiste en quartz entre-mele d’ochre martiale, de pyrite cuivreuse et galene. Cette derniere est souvent recouverte de chaux de plomb grise, et de petits cristaux de mine de plomb jaune donnant dans l’analyse un indice d’or. Ce filon finit a la reunion de la pierre calcaire au gneiss. Cette reunion se fait ici dans la direction d’une heure 6/8 de la boussole de raineur, et sous un inclinaison, occidentale de 26 degres.
“Mais ce qu’il y a de remarquable, c’est que le gneis ne participe en rien de la pierre calcaire quoiqu’il n’en soit separe que par une couche d’une pouce d’epaisseur de terre argileuse et calcaire, tandis que le rocher calcaire renferme beaucoup de fragmens de granit et de gneis, dans le voisinage de cette reunion.
“Cette observation prouve incontestablement que le granit et le gneis avoient deja acquis une durete capable de resister aux infiltration des parties calcaire, et qu’ils existoient a-peu-pres tels qu’ils sont aujourd’hui lorsque la pierre calcaire commenca a se former; autrement elle n’auroit pu saisir et envelopper des morceaux detaches de ces rochers auxquels on donne avec raison l’epithete de primitif ou de premiere formation.”
M. Schreiber continues his reasoning upon those mineral appearances, in adducing another argument, which I do not think equally conclusive. He says, “Le filon de la Gardette devoit pareillement exister avant la montagne calcaire, car s’il s’etoit forme apres, je ne voit pas la raison pour laquelle il s’y seroit arrete court, et pourquoi il ne se seroit pas prolonge dans cette espece de rocher.” It is not necessary, in the formation of a vein, that it should proceed in traversing all the strata which then are superincumbent; it is reasonable to suppose, and consistent with observation to find them stop short in proceeding from one stratum to another. Had M. Schreiber found any pieces of the vein contained in the calcareous rock, he would have had good reason for that assertion; but, to conclude that fact from grounds which do not necessarily imply it, is not to be permitted in sound reasoning, if certainty is the object, and not mere probability.
SECT. II.–The Theory confirmed from Observations made on purpose to elucidate the subject.
Having got a distinct view of the primary and secondary mineral bodies or strata of the globe, and having thus acquired a particular object to inquire after, with a view to investigate or illustrate this piece of natural history, I was considering where we might most probably succeed in finding the junction of the low country strata and alpine schistus. I inquired of Mr Hall of Whitehall, who had frequent opportunities of traversing those mountains which lie between his house in the Merse and Edinburgh; and I particularly entreated him to examine the bed of the Whittater, which he executed to my satisfaction.
Mr Hall having had occasion to examine the Pease and Tour burns, in planning and superintending the great improvement of the post road upon Sir James Hall’s estate while Sir James was abroad, he informed me that the junction of the schistus and sand-stone strata was to be found in the Tour burn. Professor Playfair and I had been intending a visit to Sir James Hall at Dunglass; and this was a motive, not so much to hasten our visit, as to chose the most proper time for a mineral expedition both upon the hills and along the sea shore.
It was late in the spring 1788 when Sir James left town, and Mr Playfair and I went to Dunglass about the beginning of June. We had exceeding favourable weather during the most part of our expedition; and I now propose to give an account of the result of our observations.
Dunglass burn is the boundary between the counties of East Lothian and Berwickshire; and it is almost the boundary between the vertical and horizontal strata. To the north-west of this burn and beautiful dean are situated the coal, lime-stone, marl, and sand-stone strata; they are found stretching away along the shore in a very horizontal direction for some time, but become more and more inclined as they approach the schistus of which the hills of Lammermuir to the south are composed.
Though the boundary between the two things here in question be easily perceivable from the nature of the country at the first inspection, by the rising of the hills, yet this does not lead one precisely to the junction; and in the extensive common boundary of those two things, the junction itself is only to be perceived in few places, where the rock is washed bare by the rivers or the sea, and where this junction is exposed naked to our view. The sea is here wearing away the coast; and the bank, about 200 feet high, is gradually falling down, making in some places a steep declivity, in others a perpendicular cliff. St Abb’s Head and Fast Castle are head lands projecting into the sea, and are the bulwarks of this shore, which is embayed to the westward, where the sea preys upon the horizontal strata. The solid strata are every where exposed either in the cliff or on the shore; we were therefore certain of meeting with the junction in going from Dunglass to Fast Castle, which is upon the schistus. But this journey can only be made by sea; and we first set out to examine the junction in the Tour and Pease burns, where we had been informed it was to be found.
In the bottom of those rivulets the sand-stone and marly strata appear pretty much inclined, rising towards the schistus country. The two burns unite before they come to the shore; and it is about midway between this junction and the bridges which are thrown over those two hollows, that the junction is to be found.
The schistus strata here approach towards vertical; and the sand-stone strata are greatly inclined. But this inclination of those two different strata are in opposite directions; neither does the horizontal section of those two different strata run parallel to the junction; that is to say, the intersection of those two different strata is a line inclined to the horizon.
At Jedburgh the schistus was vertical, and the strata horizontal; and there was interposed a compound bed of pudding-stone, formed of various water-worn bodies, the gravel of the schistus strata, and porphyries. Here again, though we have not a regular pudding-stone, we have that which corresponds to it, as having been the effect of similar circumstances. These are the fracture and detritus of the schistus, while the strata were deposited upon the broken ends of the schistus at the bottom of the sea. Most of the fragments of the schistus have their angles sharp; consequently, they had not travelled far, or been much worn by attrition. But more or less does not alter the nature of an operation; and the pudding-stone, which at Jedburgh is interposed between the vertical schistus and horizontal strata, is here properly represented by the included fragments of schistus in the inclined strata.
The line of this junction running, on the one hand, towards Fast Castle eastward, and, on the other, towards the head of Dunglass burn westward, our business was to pursue this object in those two different directions. But it was chiefly in the sea coast that was placed our expectations, having recollection of the great banks of gravel under which the strata are buried about Oldhamstocks, near which, from all appearances, the junction was to be expected.
Having taken boat at Dunglass burn, we set out to explore the coast; and, we observed the horizontal sand-stone turn up near the Pease burn, lifting towards the schistus. We found the junction of that schistus with the red sand-stone and marly strata on the shore and sea bank, at St. Helens, corresponding in general with what we had observed in the burns to the westward. But, at Siccar Point, we found a beautiful picture of this junction washed bare by the sea. The sand-stone strata are partly washed away, and partly remaining upon the ends of the vertical schistus; and, in many places, points of the schistus strata are seen standing up through among the sand-stone, the greatest part of which is worn away. Behind this again we have a natural section of those sand-stone strata, containing fragments of the schistus.
After this nothing appears but the schistus rocks, until sand-stone and marl again are found at Red-heugh above the vertical strata. From that bay to Fast Castle we had nothing to observe but the schistus, which is continued without interruption to St Abb’s Head. Beyond this, indeed, there appears to be something above the schistus; and great blocks of a red whin-stone or basaltes come down from the height and lie upon the shore; but we could not perceive distinctly how the upper mass is connected with the vertical schistus which is continued below.
Our attention was now directed to what we could observe with respect to the schisti, of which we had most beautiful views and most perfect sections. Here are two objects to be held in view, in making those observations; the original formation or stratification of the schisti, and the posterior operations by which the present state of things has been procured. We had remarkable examples for the illustration of both those subjects.
With regard to the first, we have every where among the rocks many surfaces of the erected strata laid bare, in being separated. Here we found the most distinct marks of strata of sand modified by moving water. It is no other than that which we every day observe upon the sands of our own shore, when the sea has ebbed and left them in a waved figure, which cannot be mistaken. Such figures as these are extremely common in our sand-stone strata; but this is an object which I never had distinctly observed in the alpine schisti; although, considering that the original of those schisti was strata of sand, and formed in water, there was no reason to doubt of such a thing being found. But here the examples are so many and so distinct, that it could not fail to give us great satisfaction.
We were no less gratified in our views with respect to the other object, the mineral operations by which soft strata, regularly formed in horizontal planes at the bottom of the sea, had been hardened and displaced. Fig. 4. represents one of those examples; it was drawn by Sir James Hall from a perfect section in the perpendicular cliff at Lumesden burn. Here is not only a fine example of the bendings of the strata, but also of a horizontal shift or hitch of those erected strata.
St Abb’s Head is a promontory which, at a distance, one would naturally conclude to be composed of the schisti, as is all the shore to that place; but, as we approached it, there was some difference to be perceived in the external appearance, it having a more rounded and irregular aspect. Accordingly, upon our arrival, we found this head-land composed of a different substance. It is a great mass of red whin-stone, of a very irregular structure and composition. Some of it is full of small pebbles of calcareous spar, surrounded with a coat of a coloured substance, different both from the whin-stone ground and the inclosed pebble. Here ended our expedition by water.
Having thus found the junction of the sand-stone with the schistus or alpine strata to run in a line directed from Fast Castle to Oldhamstocks, or the heads of Dunglass burn, we set out to trace this burn, not only with a view to observe the junction, if it should there appear, but particularly to discover the source of many blocks of whin-stone, of all sizes, with which the bed of this burn abounds.
The sand-stone and coal strata, which are nearly horizontal at the mouth of this burn, or on the coast, become inclined as we go up the course of the rivulet; and of this we have fine sections in the bank. The Dean of Dunglass is formed of precipitous and perpendicular rocks, through which the running water has worn its way more than a hundred feet deep; above this Dean the banks are steep and very high, but covered with soil, which here is a deep gravel. The burn runs all the way up to Oldhamstocks upon the sand-stone strata; but there, these are traversed by a high whin-stone dyke, which crosses the burn obliquely, as we found it on both banks though not in the bed of the burn; it is in the south bank below the village, and on the north above it. Here is the source of the whin-stone which we were looking for; it is the common blue basaltes, of the same nature with the Giant’s Causeway, but with no regular columner appearance.
Above Oldhamstocks we again found the sand-stone in the bank, but it soon disappeared under a deep cover of gravel, and the burn then divided into several rivulets which come from the hills. We traced the one which led most directly up to the mountains, in expectation of meeting with the schistus, at least, if not the junction of it with the sandstone. But in this we were disappointed. We did not however lose our labour; for, though the junction which we pursued be not here visible, we met with what made it sufficiently evident, and was at the same time an object far more interesting in our eyes.
I have already quoted Mr Voigt’s description of the _sol mort rouge_; he says, that in places it forms entire mountains; here we have a perfect example of the same thing; and the moment we saw it, we said, here is the _sol mort rouge_. We ascended to the top of the mountain through a gully of solid pudding-stone going into decay, and furnishing the country below with that great covering of gravel, soil, and water worn stones. We were now well acquainted with the pudding-stone, which is interposed between the horizontal and alpine strata; but from what we had seen to the eastward, we never should have dreamed of meeting with what we now perceived. What we had hitherto seen of this pudding-stone was but a few fragments of the schistus in the lower beds of sand-stone; here a mountain of water-worn schisti, imbedded in a red earth and consolidated, presented itself to our view. It was evident that the schisti mountains, from whence those fragments had come, had been prior to this secondary mass; but here is a secondary mountain equal in height to the primary, or schisti mountains, at the basis of which we had seen the strata superinduced on the shore. Still, however, every thing here is formed upon the same principle, and nothing here is altered except the scale on which the operation had been performed.
Upon the coast, we have but a specimen of the pudding-stone; most of the fragments had their angles entire; and few of them are rounded by attrition. Here, on the contrary, the mountain is one pudding-stone; and most of the fragments are stones much rounded by attrition. But the difference is only in degree, and not in kind; the stones are the same, and the nature of the composition similar. Had we seen the mass of which this mountain is only a relict, (having been degraded by the hands of time), we should have found this pudding-stone at the bottom of our sand-stone strata; could we have penetrated below this mass of pudding-stone, we should have found our schistus which we left on the shore at St. Helens and in the Tour burn. In Tiviotdale the vertical schisti are covered with a bed of pudding-stone, the gravel of which had been much worn by attrition, but the thickness of that bed is small; here again the wearing operation has been great, and the quantity of those materials even more than in proportion to those operations. We returned perfectly satisfied; and Sir James Hall is to pursue this subject farther when he shall be in those mountains shooting muir game.
We had now only one object more to pursue; this was to examine the south side of those mountains of Lammermuir upon the sea shore, in order to see the junction of the primary schistus with the coal strata of Berwickshire. Mr Hall was to meet us at the Press, and we were afterwards to go with him to Whitehall. We met accordingly; but the weather was rainy; and we went directly to Whitehall. I had often seen the pudding-stone in great masse; in the banks of the Whiteader, as it comes out of the mountains, but then I had not seen its connection neither, on the one hand, with the schisti, nor, on the other, with the sand-stone strata. We knew that at Lammerton upon the sea coast there was coal, and consequently the sand-stone strata; and reasoning upon those data we were sure that our proper course of investigation was to trace the river Ey to the shore, and then go south the coast in search of the junction of the schistus with the horizontal strata. This we executed as well as the weather would permit; but had it to regret, that the rainy season was not so favourable for our views, as it was agreeable to the country which had been suffering with the drought.
It is needless now to enlarge upon this subject. I shall only mention that we found the red marly strata above the pudding-stone in the bed of the Ey and its branches; we then traced the schistus down the Ey, and found a mass of the most consolidated pudding-stone upon the coast to the north of the harbour of Eymouth. But this mass did not rest on the schistus; it is immediately upon a mass of whin-stone; and the schistus is in the harbour, so that this whin-stone mass seems to be here interposed between the pudding-stone and schistus. We then pursued the coast southwards until we found the junction of the schistus and sand-stone strata about two miles from Eymouth; but here the junction was not attended with any pudding-stone that we could perceive.
Having found the same or similar appearances from the one end to the other, and on both sides of that range of mountains which run from sea to sea in the south of Scotland, we may now extend our view of this mineral operation in comprehending every thing of the same kind which we meet with in our island or any other distant country.
Thus perhaps the pudding-stone of the south of England will be considered in the same light as having been formed of the _debri_ and _detritus_ of the flinty bodies.
In the island of Arran, there is also a pudding-stone, even in some of the summits of the island, exactly upon the border of the schistus district, as will be described in the natural history of that island. This pudding-stone is composed of gravel formed of the hardest parts of the schistus and granite or porphyry mountains. That compound parasitical stone has been also again cemented by heat and fusion; I have a specimen in which there is a clear demonstration of that fact. One of the water-worn stones which had been rounded by attrition, has in this pudding-stone been broken and shifted, the one half slipping over the other, three quarters of an inch, besides other smaller slips in the same stone. But the two pieces are again cemented; or they had been shifted when the stone was in that soft state, by which the two pieces are made perfectly to cohere. Those shifts and veins, in this species of stone, are extremely instructive, illustrating the mineral operations of the globe.
In like manner to the north of the Grampians, along the south side of Loch Ness, there are mountains formed of the debris of schistus and granite mountains, first manufactured into sand and gravel, and then consolidated into a pudding-stone, which is always formed upon the same principle. The same is also found upon the south side of those mountains in the shire of Angus.
I may also give for example the African _Brechia_, which is a pudding-stone of the same nature. This stone is composed of granites or porphyries, serpentines and schisti, extremely indurated and perfectly consolidated. It is also demonstrable from the appearance in this stone that it has been in a softened state, from the shape and application of its constituent parts; and in a specimen of it which I have in my cabinet, there is also a demonstration of calcareous spar flowing among the gravel of the consolidated rock.
This fact therefore of pudding-stone mountains, is a general fact, so far as it is founded upon observations that are made in Africa, Germany, and Britain. We may now reason upon this general fact, in order to see how far it countenances the idea of primitive mountains, on the one hand, or on the other supports the present theory, which admits of nothing primitive in the visible or examinable parts of the earth.
To a person who examines accurately the composition of our mountains, which occupy the south of Scotland, no argument needs be used to persuade him that the bodies in question are not primitive; the thing is evident from inspection, as much as would be the ruins of an ancient city, although there were no record of its history. The visible materials, which compose for the most part the strata of our south alpine schisti, are so distinctly the _debris_ and _detritus_ of a former earth, and so similar in their nature with those which for the most part compose the strata on all hands acknowledged as secondary, that there can remain no question upon that head. The consolidation, again, of those strata, and the erection of them from their original position, and from the place in which they had been formed, is another question.
But the acknowledging strata, which had been formed in the sea of loose materials, to be consolidated and raised into the place of land, is plainly giving up the idea of primitive mountains. The only question, therefore, which remains to be solved, must respect the order of things, in comparing the alpine schisti with the secondary strata; and this indeed forms a curious subject of investigation.
It is plain that the schisti had been indurated, elevated, broken, and worn by attrition in water, before the secondary strata, which form the most fertile parts of our earth, had existed. It is also certain that the tops of our schistus mountains had been in the bottom of the sea at the time when our secondary strata had begun to be formed; for the pudding-stone on the top of our Lammermuir mountains, as well as the secondary strata upon the vertical schisti of the Alps and German mountains, affords the most irrefragable evidence of that fact.
It is further to be affirmed, that this whole mass of water-formed materials, as well as the basis on which it rested, had been subjected to the mineral operations of the globe, operations by which the loose and incoherent materials are consolidated, and that which was the bottom of the sea made to occupy the station of land, and serve the purpose for which it is destined in the world. This also will appear evident, when it is considered that it has been from the appearances in this very land, independent of those of the alpine schisti, that the present theory has been established.
By thus admitting a primary and secondary in the formation of our land, the present theory will be confirmed in all its parts. For, nothing but those vicissitudes, in which the old is worn and destroyed, and new land formed to supply its place, can explain that order which is to be perceived in all the works of nature; or give us any satisfactory idea with regard to that apparent disorder and confusion, which would disgrace an agent possessed of wisdom and working with design.
CHAP. VII.
Opinions examined with regard to Petrifaction, or Mineral Concretion.
The ideas of naturalists with regard to petrifaction are so vague and indistinct, that no proper answer can be given to them. They in general suppose water to be the solvent of bodies, and the vehicle of petrifying substances; but they neither say whether water be an universal menstruum, nor do they show in what manner a solid body has been formed in the bowels of the earth, from that solution. It may now be proper to examine this subject, not with a view to explain all those petrifactions of bodies which is performed in the mineral regions of the earth, those regions that are inaccessible to man, but to show that what has been wrote by naturalists, upon this subject, has only a tendency to corrupt science, by admitting the grossest supposition in place of just principle or truth, and to darken natural history by introducing an ill conceived theory in place of matter of fact.
M. le Comte de Buffon has attempted to explain the crystallization of bodies, or production of mineral forms, by the accretion or juxtaposition of elementary bodies, which have only form in two dimensions, length and breadth; that is to say, that mineral concretions are composed of surfaces alone, and not of bodies. This however is only an attempt to explain, what we do not understand, by a proposition which is either evidently contradictory, or plainly inconceivable. It is true that this eloquent and ingenious author endeavours to correct the palpable absurdity of the proposition, by representing the constituent parts of the mineral bodies as “_de lames infiniment minces_;” but who is it does not see, that these infinitely thin plates are no other than bodies of three dimensions, contrary to the supposition; for, infinitely thin, means a certain thickness; but the smallest possible or assignable thickness differs as much from a perfect superficies as the greatest.
M. de Luc has given us his ideas of petrifaction with sufficient precision of term and clearness of expression; his opinion, therefore, deserves to be examined; and, as his theory of petrifaction is equally applicable to every species of substance, it is necessary again to examine this subject, notwithstanding of what has been already said, in the first part of this work, concerning consolidation and mineral concretion from the fluid state of fusion.
This author has perhaps properly exposed Woodward’s Theory of Petrification in saying[33], “Son erreur a cet egard vient de ce qu’il n’a point reflechi sur la maniere dont se fait la _petrifaction_. Il ramollit d’abord les _pierres_ pour y faire entrer les coquilles, sans bien connoitre l’agent qu’il y employe; et il les duroit ensuite, sans reflechir au comment.” To avoid this error or defect, M. de Luc, in his Theory of Petrifaction, sets out with the acknowledged principle of cohesion; and, in order to consolidate strata of a porous texture, he supposes water carrying minute bodies of all shapes and sizes, and depositing them in such close contact as to produce solidity and concretion. Now, if Dr Woodward softened stones without a proper cause, M. de Luc, in employing the specious principle of cohesion, has consolidated them upon no better grounds; for, the application of this principle is as foreign to his purpose, as is that of magnetism. Bodies, it is true, cohere when their surfaces are closely applied to each other; But how apply this principle to consolidation?–only by supposing all the separate bodies, of which the solid is to be composed, to be in perfect contact in all their surfaces. But this, in other words, is supposing the body to be solid; and, to suppose the agent, water, capable of thus making hard bodies solid, is no other than having recourse to the fortuitous concourse of atoms to make a world; a thought which this author would surely hold in great contempt.
[Note 33: Lettres Physiques et Morales.]
He then illustrates this operation of nature by those of art, in building walls which certainly become hard, and which, as our author seems to think, become solid. But this is only an imperfect or erroneous representation of this subject; for, mortar does not become hard upon the principle of petrification adopted by our author. Mortar, made of clay, instead of lime, will not acquire a stony hardness, nor ever, by means of water, will it be more indurated than by simply drying; neither will the most subtile powder of chalk, with water and sand, form any solid body, or a proper mortar. The induration of mortar arises from the solution of a stony substance, and the subsequent concretion of that dissolved matter, operations purely chemical. Now, if this philosopher, in his Theory of Petrifaction, means only to explain a chemical operation upon mechanical principles, why have recourse, for an example in this subject, to mineral bodies, the origin of which is questioned? Why does he not rather explain, upon this principle, the known concretion of some body, from a fluid state, or, conversely, the known solution of some concreted body? If again he means to explain petrifaction in the usual way, by a chemical operation, in that case, the application of his polished surfaces, so as to cohere, cannot take place until the dissolved body be separated from the fluid, by means of which it is transported from place to place in the mineral regions. But it is in this preliminary step that lies all the difficulty; for, could we see how every different substance might be dissolved, and every dissolved substance separated from its solvent at our pleasure, we should find no difficulty in admitting the cohesion of hard bodies, whether by means of this doctrine of polished surfaces, or by the principle of general attraction, a principle which surely comprehends this particular, termed a cohesive power.
It must not be alleged, that seeing we know not how water dissolves saline bodies, therefore, this fluid, for any thing that we know, may also dissolve crystal; and, if water thus dissolves a mineral substance in a manner unknown to us, it may in like manner deposit it, although we may not be able to imagine how. This kind of reasoning is only calculated to keep us in ignorance; at the same time, the reasoning of philosophers, concerning petrifaction, does not in general appear to be founded on any principle that is more sound. That water dissolves salt is a fact. That water dissolves crystal is not a fact; therefore, those two propositions, with regard to the power of water, are infinitely removed, and cannot be assimilated in sound physical reasoning. It is no more a truth that water is able to dissolve salt, than that we never have been able to detect the smallest disposition in water to dissolve crystal, flint, quartz, or metals. Therefore, to allege the possibility of water being capable of dissolving those bodies in the mineral regions, and of thus changing the substance of one body into another, as naturalists have supposed, contrary to their knowledge, or in order to explain appearances, is so far from tending to increase our science, that it is abandoning the human intellect to be bewildered in an error; it is the vain attempt of lulling to sleep the scientific conscience, and making the soul of man insensible to the natural distress of conscious ignorance.
But besides that negative argument concerning the insolubility of crystal, by which the erroneous suppositions of naturalists are to be rejected, crystal in general is found regularly concreted in the cavities of the most solid rock, in the heart of the closest agate, and in the midst of granite mountains. But these masses of granite were formed by fusion; I hope that I shall give the most satisfactory proof of that truth: Consequently, here at least there is no occasion for the action of water in dissolving siliceous substances in one place, in order to concrete and crystallise it in another.
In these cavities of the solid granite rock, where crystal is found regularly shooting from a basis which is the internal surface of the cavity, we find the other constituent substances of the granite also crystallised. I have those small cavities, in this rock, from the island of Arran, containing crystal, felt-spar, and mica, all crystallised in the same cavity[34]. But this is nothing to the _druzen_ or crystalline concretions, which are found in a similar manner among metallic and mineral substances in the veins and mines; there, every species of mineral and metallic substance, with every variety of mixture and composition, are found both concreted and crystallised together in every imaginable shape and situation.
[Note 34: The Chevalier Dolomieu makes the following observation. Journal de Physique, Juillet 1791.
“J’ai ete etonne de trouver au centre d’un enorme massif de granit, que l’on avoit ouvert avec la poudre pour pratiquer un chemin, des morceaux, gros comme le poing et au dessous, de spath calcaire blanc, tres-effervescent, en grandes ecailles, ou lames entrecroisees. Il n’occupoit point des cavites particulieres, il n’y paroissoit le produit d’une infiltration qui auroit rempli des cavites, mais il etoit incorpore avec les feld-spath, le mica, et le quartz, faissoit masse avec eux, et ne pouvoit se rompre sans les entrainer avec lui.”
This great naturalist is convinced that the spar had not been here introduced by infiltration, although that is the very method which he employs to form concretions, not only of spar but of crystal, zeolite, and pyrites, in the closest cavities of the most solid rocks of basaltes. These four substances in this stone were so mixed together that nothing but the fusion of the whole mass could explain the state in which they appeared; but, thinking that such a supposition could not be allowed, this naturalist, like a man of science when his data fail, leaves the matter without any interpretation of his own. This however is what he has not done in the case of basaltes, or that which he mistakes for proper lavas, as I shall have occasion to show.]
Here is an infinite operation, but an operation which is easily performed by the natural arrangement of substances acting freely in a fluid state, and concreting together, each substance, whether more simple or more compound, directing itself by its internal principle of attraction, and affecting mechanically those that are concreting around it.
We see the very same thing happen under our eye, and precisely in the same manner. When a fluid mass of any mineral or metallic substance is made to congeal by sudden cooling on the outside, while the mass within is fluid, a cavity is thus sometimes formed by the contraction of the contained fluid; and in this cavity are found artificial _druzen_, as they may be called, being crystallizations similar to those which the mineral cavities exhibit in such beauty and perfection.
Petrification and consolidation, in some degree, may doubtless be performed, in certain circumstances, by means of the solution of calcareous earth; but the examples given by M. de Luc, of those bodies of lime-stone and agate petrified in the middle of strata of loose or sandy materials, are certainly inexplicable upon any other principle except the fusion of those substances with which the bodies are petrified[35].
[Note 35: Vid. Lettre 28 et Lettre 103. Lettres Physiques et Morales.]
This subject deserves the strictest attention; I propose it as a touchstone for every theory of petrification or perfect consolidation. First, There are found, among argillaceous strata, insulated bodies of iron-stone, perfectly consolidated; secondly, There are found, in strata of chalk and lime-stone, masses of insulated flints; thirdly, There are found, in strata of sea sand, masses of that sand cemented by a siliceous substance; fourthly, In the midst of blocks of sand-stone, there are found masses of loose or pure sand inclosed in crystallised cavities; and in this sand are found insulated masses of crystallised spar, including within them the sand, but without having the sparry or calcareous crystallization disturbed by it. There are also other globular masses of the same kind, where the sparry crystallization is either not to be observed, or appears only partially[36]: And now, lastly, In strata of shell-sand, there are found masses of consolidated lime-stone or marble. In all those cases, the consolidated bodies are perfectly insulated in the middle of strata, in which they must of necessity have been petrified or consolidated; the stratum around the bodies has not been affected by the petrifying substance, as there is not any vestige of it there; and here are examples of different substances, all conspiring to prove one uniform truth. Therefore, a general theory of petrification or consolidation of mineral bodies must explain this distinct fact, and not suffer it any longer to remain a _lusus naturae_.
[Note 36: Mem. de l’Academie Royale des Sciences, an. 1775.]
Let us now consider what it is that we have to explain, upon the supposition of those concretions being formed from a solution. We have, first, To understand what sort of a solution had been employed for the introducing of those various substances; secondly, How those concretions had been formed from such solutions within those bodies of strata; and, lastly, How such concretions could have been formed, without any vestige appearing of the same substance, or of the same operation, in the surrounding part of the stratum. Whatever may be the difficulty of explaining those particular appearances by means of fusion and mechanical force, it is plainly impossible to conceive those bodies formed in those places by infiltration, or any manner of concretion from a state of solution.
Naturalists, in explaining the formation of stones, often use a chemical language which either has no proper meaning, or which will not apply to the subject of mineral operations. We know the chemical process by which one or two stony concretions may be formed among bodies passing from one state to another. When, therefore, a change from a former state of things in mineral bodies is judged by naturalists to have happened, the present state is commonly explained, or the change is supposed to have been made by means of a similar process, without inquiring if this had truly been the case or not. Thus their knowledge of chemistry has led naturalists to reason erroneously, in explaining things upon false principles. It would be needless to give an example of any one particular author in this respect; for, so far as I have seen, it appears to be almost general, every one copying the language of another, and no one understanding that language which has been employed.
These naturalists suppose every thing done by means of solution in the mineral kingdom, and yet they are ignorant of those solvents. They conceive or they imagine concretions and crystallizations to be formed of every different substance, and in every place within the solid body of the earth, without considering how far the thing is possible which they suppose. They are constantly talking of operations which could only take place in the cavities of the earth above the level of the sea, and where the influence of the atmosphere were felt; and yet this is the very place which we have it in our power to examine, and where, besides the stalactite, and one or two more of the same kind, or formed on the same principle, they have never been able to discover one of the many which, according to their theory, ought always to be in action or effect. So far from knowing that general consolidating operation, which they suppose to be exerted in filling up the veins and cavities of the earth by means of the infiltrating water of the surface, they do not seem fully to understand the only operation of this kind which they see. The concretion of calcareous matter upon the surface of the earth is perhaps the only example upon which their theory is founded; and yet nothing can be more against it than the general history of this transaction.
Calcareous matter, the great _vinculum_ of many mineral bodies, is in a perpetual state of dissolution and decay, in every place where the influences of air and water may pervade. The general tendency of this is to dissolve calcareous matter out of the earth, and deliver that solution into the sea. Were it possible to deny that truth, the very formation of stalactite, that operation which has bewildered naturalists, would prove it; for it is upon the general solubility of calcareous matter exposed to water that those cavities are formed, in which may be found such collections of stalactical concretion; and the general tendency of those operations is to waste the calcareous bodies through which water percolates. But how is the general petrifaction or consolidation of strata, below the surface of the sea, to be explained by the general dissolution of that consolidating substance in the earth above that level? Instead of finding a general petrifying or consolidating operation in the part of the earth which we are able to examine, we find the contrary operation, so far at least as relates to calcareous spar, and many other mineral bodies which are decomposed and dissolved upon the surface of the earth.
Thus in the surface of the earth, above the level of the sea, no petrifying operation of a durable nature is found; and, were such an operation there found, it could not be general, as affecting every kind of substance. But, even suppose that such a general operation were found to take place in the earth above the level of the sea, where there might be a circulation of air and percolation of water, How could the strata of the earth below the level of the sea be petrified? This is a question that does not seem to have entered into the heads of our naturalists who attempt to explain petrifaction or mineral concretion from aqueous solutions. But the consolidation of loose and incoherent things, gathered together at the bottom of the sea, and afterwards raised into rocks of various sorts, forms by far the greatest example of petrification or mineral operation of this globe. It is this that must be explained in a mineral theory; and it is this great process of petrifaction to which the doctrine of infiltration, whether for the mechanical purpose of applying cohesive surfaces, or the chemical one of forming crystallizations and concretions, will not by any means apply.
Nothing shows more how little true science has been employed for the explanation of phenomena, than the language of modern naturalists, who attribute, to stalactical and stalagmical operations, every superficial or distant resemblance to those calcareous bodies, the origin of which we know so well. It is not a mere resemblance that should homologate different things; there should be a specific character in every thing that is to be generalised. It will be our business to show that, in the false stalactites, there is not the distinctive character of those water formed bodies to be found.
In the formation of stalactical concretions, besides the incrustation as well as crystallization of the stony substance from the aqueous vehicle by which it had been carried in the dissolved state, we have the other necessary accompanyments of the operation, or collateral circumstances of the case. Such, for example, is that tubular construction of the stalactite, first formed by the concretion of the calcareous substance upon the outside of the pendant gut of water exposed to the evaporation of the atmosphere; we then see the gradual filling up of that pervious tube through which the petrifying water had passed for a certain time; and, lastly, we see the continual accretion which this conducting body had received from the water running successively over every part of it. But among the infinite number of siliceous concretions and crystallizations, as well as those of an almost indefinite variety of other substances, all of which are attributed to solution, there is not the least vestige of any collateral operation, by which the nature of that concretion might be ascertained in the same manner. In all those cases, we see nothing but the concreted substances or their crystallizations; but, no mark of any solvent or incrusting process is to be perceived. On the contrary, almost all, or the greatest part of them, are so situated, and attended with such circumstances, as demonstrate the physical impossibility of that being the manner in which they had been concreted; for, they are situated within close cavities, through which nothing can pervade but heat, electricity, magnetism, etc.; and they fill those cavities more or less, from the thinnest incrustation of crystals to the full content of those cavities with various substances, all regularly concreted or crystallised according to an order which cannot apply to the concretion of any manner of solution.
That there is, in the mineral system, an operation of water which may with great propriety be termed _infiltration_, I make no doubt. But this operation of water, that may be employed in consolidating the strata in the mineral regions, is essentially different from that which is inconsiderately employed or supposed by mineralists when they talk of infiltration; these two operations have nothing in common except employing the water of the surface of the earth to percolate a porous body. Now, the percolation of water may increase the porousness of that body which it pervades, but never can thus change it from a porous to a perfect solid body. But even the percolation of water through the strata deposited at the bottom of the sea, necessarily required, according to the supposition of naturalists, must be refused; for, the interstices of those strata are, from the supposition of the case, already filled with water; consequently, without first removing that stagnant water, it is in vain to propose the infiltration of any fluid from the surface.
This is a difficulty which does not occur in our theory, where the strata, deposited at the bottom of the sea, are to be afterwards heated by the internal fires of the earth. The natural consequence of those heating operations may be considered as the converting of the water contained in the strata into steam, and the expulsion of steam or vapour, by raising it up against the power of gravity, to be delivered upon the surface of the earth and again condensed to the state of water.
Let us now conceive the strata, which had been deposited at the bottom of the sea, as exhausted of their water, and as communicating with the surface of the earth impregnated with water. Here again we have the power of gravity to operate in carrying down water to that place which had been before exhausted by the power of heat; and in this manner, by alternately employing those two great physical agents, we cannot doubt that nature may convey soluble substances from above, and deposit them below for the purpose of consolidating porous bodies, or of filling with saline and earthy matter those interstices which had been originally filled with water, when the strata were deposited at the bottom of the sea. How far any marks of this operation may be perceived, by carefully examining our mines and minerals, I know not; I can only say that, on the contrary, whenever those examined objects were clear and distinct, with the concomitant circumstances, so as to be understood, I have always found the most certain marks of the solid bodies having concreted from the fluid state of fusion. This, however, does not exclude the case of infiltration having been previously employed; and I would intreat mineralists, who have the opportunity of examining the solid parts of the earth, to attend particularly to this distinction. But do not let them suppose that infiltration can be made to fill either the pores or veins of strata without the operation of mineral heat, or some such process by which the aqueous vehicle may be discharged.
Not only are mineral philosophers so inconsiderate, in forming geological theories upon a mere supposition or false analogy, they have even proceeded, upon that erroneous theory, to form a geological supposition for explaining the appearances of strata and other stony masses in employing a particular physical operation, which is, that of _crystallization_[37]. Now crystallization may be considered as a species of elective concretion, by which every particular substance, in passing from a fluid to a solid state, may assume a certain peculiar external shape and internal arrangement of its parts, by which it is often distinguished. But, to suppose the solid mineral structure of the earth explained, like an enigma, by the word _crystallization_, is to misunderstand the science by which we would explain the subject of research; and, to form a general mineral theory thus upon that term, is an attempt to generalise without a reason. For, when it were even admitted that every solid body is crystallised, we thus know no more of the geology of this earth, or understand as little of the general theory of mineral concretion, as we did before;–we cannot, from that, say whether it be by the operation of solution or of fusion which had produced the perceived effect.
[Note 37: Journal de Physique; Avril 1753.]
M. de Carosi has wrote a treatise upon certain petrifactions[38]. In the doctrine of this treatise there is something new or extraordinary. It will therefore be proper to make some observations on it.
[Note 38: Sur la Generation du Silex et du Quartz en partie. Observations faites en Pologne 1783, a Cracovie.]
The object of this treatise is to describe the generation of silex and quartz, with their modifications or compositions, formed within mineral bodies of a different substance. The natural history contained in this little treatise is well described and sufficiently interesting. But It is chiefly in order to examine the means which, according to the theory of this treatise, are employed in petrifying bodies, that I consider it in this place.
The first section of this treatise has for title, _Generation du Caillou et du Quartz de la terre calcaire pure_. It may be worth while to compare the natural history of this part of the earth with the flint and chert found in our chalk and lime-stone countries. I shall therefore transcribe what is worth observing upon that subject (p. 5.).
“Nous rencontrons chez nous dans les parties le plus montagneuses, et les moins couvertes de terreau, ou tout-au plus de sable, entre de purs rochers calcaires une quantite incroyable de cailloux (silex) tant en boules, que veines, couches, et debris. Au premier coup d’oeil l’on s’imagine que ce font des debris de montagnes eloignees, qui y furent amenes par les eaux, mais, en examinant la chose de plus pres, on est convaincu, que ce sont tout au contraire, des parties detachees des montagnes de la contree. Car il y a sur presque toute l’etendue de nos montagnes calcaires une couche, ou pour mieux dire, un banc compose de plusieurs couches de base calcaire, mais qui ou sont parsemees irregulierement de boules, de rognons, de veines, et de petits filons de silex, ou qui contiennent cette pierre en filon, veines, et couches paralleles, et regulierement disposees. Les boules et rognons de silex y font depuis moins de la grandeur d’une petite noisette, jusqu’au diametre de plus de six pouces de notre mesure. La plupart de ces boules tant qu’elles sont dans l’interieur cache de la roche vive, et qu’elles n’ont rien souffert de l’impression de l’air, ont, pour l’ordinaire, une croute de spath calcaire, au moyen de la quelle elles sont accrues a la roche mere; ou pour mieux dire la croute spatheuse fait l’intermede entre le silex, et la roche calcaire, par ou se fait le passage de l’une a l’autre. Mais ceci ne vaut que de boules de silex entierement formees. C’est dont on peut meme se convaincre a la vue, par beaucoup de pierres dont le pave de la ville de Cracovie est compose. Mais la, ou le silex n’est pas encore entierement acheve, la croute spatheuse manque, en revanche on y voit evidemment le passage par degres successifs de la roche calcaire au silex qui y est contenu, et les nuances de ce passage sont souvent si peu marquees que meme les acides mineraux ne suffisent pas a les determiner, ce n’est que le briquet, qui nous aide a les decouvrir. On voit bien ou la pierre calcaire s’enfonce en couleur, l’on s’appercoit, ou sa durete, ses cassures changent, mais, comme elle y souffre encore quelque impression des acides, l’on ne sauroit determiner au juste le point, ou elle a deja plus de la nature du silex, que de celle de la chaux, qu’en la frappant du briquet.
“Tels sont les cailloux en boules et rognons avant leur etat de perfection, il y aura meme au milieu une partie de pierre calcaire non changee.
“Ceux au contraire, ou la nature a acheve son ouvrage, ont une croute de chaux endurcie, et sont purement du silex fini, mais de toutes couleurs, d’un grain et d’une texture plus ou moins fine, qui passe assez souvent par degres dans les differentes varietes du noble silex. Ils ont, pour l’ordinaire, dans leur interieur une cavite, mais pas toujours au centre, et qui vient apparemment de la consommation de cette partie calcaire qui y resta la derniere, et n’en fut changee ou dissolute et separee, que lorsque le reste du silex etoit deja entierement fini. Ces cavites sont toujours, ou enduites de calcedoine en couche concentriques recouverte de petits cristaux fort brillans et durs de quartz, ou bien seulement de ces derniers-ci. Par-fois il y a aussi du spath calcaire crystallise, mais cela est extremement rare. Quelque-fois enfin ces cavites sont remplies d’une noix de calcedoine. Je n’ai reussi qu’une seule fois en cassant un pareil silex en boule d’y trouver encore le reste de l’eau de crystallisation.”
The only remark that I would here make is this, that, if the crystallization of those close cavities in the _silex_ had at any time required water of solution, it must always have required it. But, if there had been water of solution contained in those close cavities, for the crystallization of the various things which are often found within them, How comes it that this water is almost never found? I have good reason to believe that water contained within a solid flint will not make its escape, as does that contained in the _anhydrites_ of Mount _Berico_, which are composed of a porous calcedony. But the siliceous crystallizations within close cavities is a curious subject, which we shall have occasion to examine more particularly in treating of agates. We now proceed to the next section, which is the generation of silex and quartz in marl, (p. 19.)
“Il y a des contrees, chez nous, qui out des etendus assez considerables en long et en large, de montagnes de pierre de marne calcaire, dans lesquelles on rencontre le meme phenomene que dans celles de chaux pure; c. a. d. nous y trouvons du silex de differentes varietes, et dans tous les degres successifs de leur formation, et de leur perfection. Outre cela, nous y voyons encore quelque chose, qui semble nous conduire a la decouverte des moyens, dont se sort la nature pour effecteur cette operation, et qui nous etoit cache dans les montagnes de chaux pure: ces bancs de pierre marnesilicieuse, contiennent une partie considerable de pyrites sulfureuses, qui non seulement y forment une grande quantite de petits sillons, mais toute la masse de la montagne est rempli de parcelles souvent presqu’imperceptibles de ce mineral. Ces pyrites sont evidemment des productions du phlogistique et de l’acide contenu dans la montagne.
“L’eau, qui s’y trouve ordinairement en assez grande abondance, en detacha, extraha d’un et l’autre, et les combina apres tous les deux ensemble. Cette meme eau les dissout derechef, et en fait de nouvelles combinaisons. C’est ce qu’on voit evidemment la, ou la nature, ayant commence ses operations, il n’y est reste de la pyrite, qu’une portion de la partie inflammable liee a une base terrestre. Dans ces endroits la marne n’est que fort peu sensible aux acides, et de blanche qu’elle etoit, sa couleur est devenue presque noire. C’est la qu’on observe les differens degres du changement de la marne en silex, contenant, meme encore, par fois, de parties pyriteiques non detruites dans son interieur. Et comme la nature forme ici, de meme, que dans la chaux pure les silex, la plupart en boules ou rognons; comme les different degres de metamorphoses de la marne en silex, sont ici beaucoup plus nombreuses que la, de sorte qu’il y a des bandes entieres, qui meriteroient plutot d’etre appelles bandes silicieuses, que marneuses; comme il y a, enfin, une grande quantite de pyrites, qu’ailleurs, il est tres probable qu’elle se serve la du meme moyen qu’ici pour operer la metamorphose en question.
“Ne nous precipitons, cependant, pas a en tirer plus de consequences; poursuivons plutot le fil de notre recit.
“Le silex, qui se trouve ici, est non seulement de differents degres de perfection, il est de plus d’une espece. Il y a de la pierre a feu, 2 de la calcedoine, 3 des agathes, et 4 differentes nuances et passages des especes ordinaires aux fines du silex.
“La pierre a feu, est, ordinairement dans son etat de perfection d’un grain assez fin, d’une couleur grise plus ou moins foncee, et meme donnant, dans le noiratre, plus ou moins diaphane; ses cassures sont concentriques ou coquillees, et sa masse est assez compacte. Outre sa conformation ordinaire en boules et rognons, elle fait presque toujours la noix de ursins marins, qui y font en grand nombre, et dont la coquille est le plus souvent, et presque toujours de spath calcaire, meme au milieu d’une boule de silex parfait.
“Les calcedoines et agathes de ces couches sont toujours (au moins, je ne les ai pas encore vues autrement) de coraux et autres corps marins petrifies. Donc, il faut que les couches de pierres roulees, d’ou j’ai tire ma collection citee plus haut, soyent des debris de montagne” detruites de cette espece. Il y en a qui sont tres parfaites comme celles qui composent ma collection, d’autres meritent plutot d’etre rangees parmi les passages du silex ordinaire, et ses especes plus fines; d’autres encore sont, en effet, de vraies agathes, mais qui renferment dans leur interieur plus ou moins de parties non parfaites presque calcaires, qui s’annoncent d’abord par leur couleur blanche, par leur gros grains relativement au reste, par leur opacite, par leur mollesse respective, et souvent meme par leur sensibilite pour les acides mineraux. Mais celles, qui sont finies, quoiqu’elles ayent, pour la plupart, une couleur presque noire, ne laissent, cependant, pas d’avoir aussi des teintes plus claires comme brunatres, verdatres, rougeatres, jaunatres, bleuatres, tachetees, veinees, etc. Leur clarte n’est pas moins variable, que leur couleur, il y en a de presqu’opaques, comme aussi de presque transparentes, sur tout la, ou la calcedoine predomine.
“Le quartz s’y trouve comme dans les pierres de la premiere section, c, a, d, crystallise, en groupes dans de petites cavites; quelquefois aussi en veines. La calcedoine y est de meme, ou bien en mamelons, ou bien en stalactites, lorsqu’elle a de la place pour s’y deposer.
“Un phenomene encore plus curieux que cela est cette belle pyrite sulphureuse jaune, comme de l’or, qui est quelquefois parsemee par tout la substance de petrifications agathisees, et qui apparemment y fut deposee apres la dite metamorphose a la faveur des petits pores, qui y etoient restes ouverts.”
I would beg that mineralists, who use such language as this, would consider if it contains a distinct idea of the operation which they would thereby describe, or if it does not contain either a contradiction or an inconceivable proposition. It supposes a calcareous body to be metamorphosed, somehow by means of the mountain acid, into a siliceous body. But, finding many bodies of pyrites contained within that solid flint, it is said, that, when the calcareous body was flintified, there were left in it cavities which were afterwards filled with pyrites. Let us reflect a moment upon this doctrine. These cavities were first open to the outside of the flinty body; but now the pyrites with which they had been filled is insulated in the solid flint. Here three things are required; first, The calcareous body is to be flintified, at the same time leaving the body full of small cavities open to the outside; secondly, These cavities are to be filled with pyrites; lastly, These mineral bodies are to be so inclosed within the flint, as to leave no vestige of the former processes. This marly mountain itself, which had been formed of loose materials gathered together at the bottom of the sea, was first to be filled with pyrites, in various shapes, by means of the phlogistic and the acid of the mountain. Here is proposed to us an operation which is totally unknown, or of which we have no kind of idea. But, let us suppose pyrites formed in this mountain, (of whatever chemical substances), by means of water; Why should water again undo that pyrites, in order to form other concretions? And, Why should the flint be formed first with cavities, and then made solid, after pyrites had been introduced into those cavities of the agate, and, as our author expresses it, _parsemee pour toute la substance?_ Here are suppositions which are not only perfectly gratuitous, but are also inconsistent with any thing that we understand. This is not explaining nature; it is only feigning causes[39].
[Note 39: The description of those insulated siliceous bodies, containing in their closed cavities all the usual concretions of calcedony and crystals, as well as full of small pyrites floating in the solid flint, are extremely interesting to a mineral system, or such a geological theory as should explain the present state of things in those strata that had been formed by deposits of known materials at the bottom of the sea; they are indeed such appearances as may be found, more or less, in all consolidated strata. But it is this author’s explanation of that petrifaction which is our present object to consider; and, as he is so particular in giving us his theory upon the subject, it is easy to detect the error of his reasoning. Were those naturalists who explain things only in general, by saying that water is the agent, and infiltration the means employed by nature;–were these naturalists, I say, to give us as particular a description of their process, it would appear as inconsistent with the nature of things as that which we have from this author, who examines nature very minutely, and who sees distinctly that the infiltrating theory is inapplicable for the explanation of those petrifactions.]
The third section has for title, “_Generation du Silex et Quartz de la Pierre Puante_.” Here we find an example worthy of being recorded, as contributing to throw great light upon those mineral operations; however, the opinion of our author and mine, upon this subject, differ widely. He proceeds thus:
“Cette pierre n’est, comme chacun le scait, qu’une pierre calcaire contenant du bitume.
“Nos montagnes n’en contiennent seulement pas de simples couches, mais il y en a meme de grandes bancs fort epais.
“Le caillou, ou silex qui s’y genere, forme, tantot de gros blocs informes, qui occupent des cavites dans l’interieure des montagnes, tantot, enfin, en forme de filons.
“J’ai remarque cette metamorphose sur trois endroits differens, dans chacun des quels la nature a autrement opere.
“Sur l’un, la pierre puante fait un banc horizontal dans une montagne de pierre calcaire crystalline, ou d’une espece de marbre, qui contient des couches et filons de metal. Ce banc de pierre puante y fait le toit d’une couche de galene de plomb et de pierre calaminaire, et dans ses cavites et fentes il y a non seulement des blocs de grandeur differente, mais aussi des veines et petites bandes courtes de silex, tant ordinaire, que noble c, a, d, de la pierre a feu, de calcedoine, d’agathes, et meme d’une espece de cornaline jaune et rouge pale. Je ne m’arreterai pas a en detailler les varietes, parce qu’elles sont trop accidentelles. Je ne les connois pas meme toutes, il s’en faut de beaucoup, parce qu’elles se trouvent dans des anciennes mines negligees, peut etre depuis plus d’un siecle, et par consequent peu accessibles. Je ne doute, cependant pas, que, si l’on pouvoit mieux sonder le terrain, on y trouveroit bien plus encore du peu que j’ai cite. Parmi ce silex, il y a aussi de petites groupes et de petites veines de quartz solide et crystallise.
“Au second endroit la pierre puante fait un filon, ou si l’on veut, une couche ou bande verticale, qui partage la montagne en deux parties presqu’egales de l’epaisseur de trois aunes a peu pres. La montagne, ou cela se voit est aussi une ancienne mine de cuivre et de plomb, consistant en plusieurs varietes de marbre, different en couleur et en grain, deposees par couches les unes sur les autres. Le filon de silex est forme de feuilles alternatives de pierre puante et de silex, tous les deux de couleur brun de bois a peu pres; mais le silex est plus fonce que sa compagne. Ces feuilles alternatives, consistent d’autres bien plus minces encore, qui souvent n’ont pas l’epaisseur d’une ligne, mais ce qu’il y a de plus curieux, c’est que la meme feuille est d’un but de pierre porque, qui, vers le milieu, passe successivement en silex, qui, a son tour, vers l’autre but, qui etoit expose a l’air repasse par les memes gradations en une espece de tuffe calcaire. Ce qui nous fait voir evidemment la generation et la destruction du silex, meme avec une partie des moyens par lesquels elle s’opere. Comme l’endroit de cette decouverte n’est accessible qu’a la superficie, je ne saurois dire s’il y a d’autres varietes de silex outre la dite. Il l’est a supposer autant par analogie, que par quelques morceaux qui ont de petites veines transversales d’une espece de calcedoine, et qui sont, meme, sur leur fentes, garnis de petits cristaux de roche. Mais ce qu’il y a de sur c’est que ce filon, parvenu a une certaine profondeur, s’ennoblit et contient du metal, c. a. d. de la galene de plomb, et de la pyrite cuivreuse, j’y en ai trouves de morceaux, qui en font de preuves incontestables. Le caillou d’ici est un grain fin d’une texture forte, peu transparent, donne beaucoup d’etincelles au briquet, mais ses cassures sont ecailleuses.
“La montagne calcaire du troisieme lieu a une couche de pierre puante epaisse de plusieurs aunes, qui, derechef contient de petites couches irregulieres et des bandes transversales de silex, qui ont jusques a six pouces passes d’epaisseur. La pierre puante est d’une couleur gris-brune, d’un grain assez fin, et d’un tissu assez dur; ses cassures sont irregulieres, mais plus la pierre s’approche du silex, plus elles donnent dans le coquille. Le silex ordinaire est d’un brun de bois, d’un grain assez fin, et d’un tissu resistant, et ses cassures sont egales a la pierre porque. Ce n’est pas la la seule variete, il y a, aussi, de la calcedoine et des agathes de couleurs differentes. Meme la pierre a feu est assez souvent traversee de veines de calcedoine, de quartz crystallise, et de spath calcaire blanc en feuilles et en crystaux. Il arrive que la meme veine est composee de ces trois especes de pierres a la fois, de sorte que l’une semble passer dans l’autre, parce que les limites reciproques sont, souvent, assez indistinctes. Il est evident, que le silex est forme de la pierre puante, parce qu’on remarque ici les memes phenomenes dont j’ai parle plus haut, c. a. d. les passages successifs de l’une dans l’autre pierre, tant en montant qu’en descendant.”
There is nothing particular in the siliceous mixture in this species of lime-stone, except the vein of that substance. It is evident that this vein, traversing the mountain, had been introduced in the fluid state of fusion. I do not mean to say, that, in this particular case now described, the evidence of that truth peculiarly appears; but that, from the general nature of mineral veins breaking and traversing the solid strata of the globe, no other conclusion can be formed; and that in the particulars of this example there is nothing that could lead us to suppose any other origin to the petrifactions contained in this vein of stinking lime-stone. It is plain, that our author has imagined to himself an unknown manner of executing his mineral metamorphoses. He sees plainly that the common notion of infiltration will not at all explain the evident confusion of those calcareous and siliceous bodies which appear to him to be metamorphosing into each other. Nothing, indeed, can explain those phenomena but a general cause of fluidity; and there is no such general cause besides that of heat or fusion.
But to show how mineralists of great merit, gentlemen who have examined systematically and with some accuracy, may impose upon themselves in reasoning for the explanation of mineral appearances from limited notions of things, and from the supposition of these having been formed where they now are found, that is, upon the surface of the earth, I would beg leave to transcribe what this author has said upon this species of petrifaction. It is not that he is ignorant of what mineralists have already said upon the subject; it is because he sees the incompetency of their explanations in those particular cases; and that he would employ some other more effectual means. (p. 50.)
“Toute terre calcaire a changer dans une autre doit, avant toute chose, etre rendue refractaire ce qui ne peut se faire qu’en la saturant avec un acide. Mais une terre simplement, saturee d’un acide, est d’une reduction fort aisee, vu que l’acide n’y tient pas trop fort, d’ailleurs ce n’est qu’un sel neutre terreux fort facile a dissoudre dans une quantite suffisante d’eau. Or pour rendre cette union plus constante, il faut que la terre alcaline s’assimile intimement a l’acide, ce qui ne se sera jamais sans un intermedeliant, qui homogene les parties de ce nouveau corps, et pour que cela ce fasse il est indispensable, qu’il s’opere une dissolution fonciere des parties terrestres de la chaux, qui facilite l’ingress a l’acide, et a l’intermede pour qu’ils s’y lie bien fortement. Supposons qu’il se forme une liqueur savonneuse de l’acide et du phlogistique, que l’air fixe, mis en liberte, ouvre les interstices des parties qui constituent la terre alcaline, qu’apres cela cette liqueur savonneuse ayant l’entree libre s’assimile a la terre en proportion requise, que l’eau, qui servoit de vehicule dans cette operation, s’evapore successivement, et emporte le superflu des ingrediens, pour qu’il se puisse operer le rapprochement le plus exacte des parcelles ou molecules homogenees de nouveau corps qu’enfin les molecules les plus pures et les mieux affinees soyent reunies en forme liquide dans des cavites, et que par l’evaporation et separation de l’eau, ou elles nageoient, il s’en forme des crystaux n’aurons-nous pas une boule de silex, avec de crystaux de quartz dans ses creux interieurs.”
The supposed case is this; a calcareous body is to be metamorphosed into a siliceous nodule, having a cavity within it lined with quartz, crystals, etc. M. de Carosi means to inform us how this may be done. Now, as this process requires no other conditions than those that may be found upon the surface of this earth, the proper way to prove this hypothetical theory, would be to exhibit such a mineral body produced by those means. But, even supposing that such a process were to be exhibited, still it would remain to be explained, how this process, which requires conditions certainly not be found at the bottom of the sea, could be accomplished in that place, where the strata of the earth had been deposited, accumulated, consolidated, and metamorphosed.
This mineral process, which has been now described, will no doubt revolt the opinions of many of our chemists as well as naturalists; and I should not have thought of transcribing it, but as an example of that inconclusive reasoning which prevails in mineralogical writings upon this subject.
But this is not all. We have, upon this occasion, a most remarkable example of the fallaceous views that may be taken of things; and of the danger to science when men of sense and observation form suppositions for the explanation of appearances without that strict conformity with the principles of natural philosophy which is requited on all occasions. Both M. de Carosi, and also M. Macquart[40], to whom our author communicated his ideas and proper specimens, assert, that from their accurate experience, they find calcedony growing daily, not only in the solid body of gypsum, etc. while in the mine, but also in the solid stone when taktn out of the mine, and preserved in their cabinet.
[Note 40: Vid. Essais de Mineralogie par M. Macquart.]
What answer can be made to this positive testimony of these gentlemen, by a person who has not seen any such a thing, and who has not the opportunity of examining the cases in which those naturalists may have perhaps been led into some delusion? Were I however to conjecture upon a subject in which I have not any positive information, I should suppose that some part of the calcedony, like the _oculus mundi_ when dipped in water, may be so transparent, while containing some portion of humidity, that it is not easily distinguishable from the gypsum in which it is concreted; but that in having the humidity evaporated, by being taken out of the mine and exposed to the dry air, those portions of calcedony, which did not before appear, may be perceived by becoming more opaque[41].
[Note 41: From the description given in this treatise, and from the drawings both of M. de Carosi and M. Macquart, I find a very valuable inference to be made, so much the more interesting, as I have not found any example of the like before. This arises from the intimate connection which is here to be perceived between agate and gypsum. Now, upon this principle, that the agate-calcedony had been formed by fusion, a truth which, from the general testimony of minerals, I must presume, it is plain, that those nodules of gypsum had been in the fluid state of fusion among those marly strata, and that the gypseous bodies had been penetrated variously with the siliceous substance of the calcedony.
The description of those siliceous penetrations of gypsum is followed by this conclusion: “En voila assez, je crois pour faire voir que le silex ci-decrit est effectivement une emanation du gypse, et non pas une matiere heterogene amenee d’autre part et deposee, ou nous la voyons.” In this instance our author had convinced himself that the calcedony concretions had not been formed, as he and other mineralists had before supposed, by means of infiltration; he has not, however, substituted any thing more intelligible in its stead. I do not pretend that we understand mineral fusion; but only that such mineral fusion is a thing demonstrable upon a thousand occasions; and that thus is to be explained the petrification and consolidation of the porous and naturally incoherent strata of the earth.]
There is, however, a subject in which I can more freely accuse this author of being deceived. This naturalist says, that calcareous stones become silex by a certain chemical operation; and that those flinty bodies, in being exposed upon the surface of the earth, out of their natural bed, are again, by a contrary chemical operation, changed from flint to a calcareous substance. I will give it in his own words, (p. 56.)
“Cela dit, venons au fait. Tout silex progenere de chaux, detache de son lieu natal, et expose aux changemens de saisons, s’amollit, recoit de crevasses, perd sa transparence, devient, enfin, tout-a-fait opaque, le phlogistique s’en evapore, l’acide en est detache, lave, et de terre vitrescible, qu’il etoit, il redevient chaux, comme il etoit auparavant.”
Here is no question with regard to mere opinion, but to matter of fact; and, in this case, nothing is more evident, than that upon the surface of this earth, that is, in the examinable parts above the level of the sea, there is no transition either of calcareous bodies into flint, nor of flinty bodies into calcareous substance. Calcareous matter is constantly dissolved by water, when it is exposed to the washing of that fluid; and it is even dissolved out of the most perfect union or combination with siliceous substance, and the most solid composition of an insoluble body, as may be perceived in the decaying of feld-spar. A superficial view of flints, which have come out of a body of chalk, may have created such an opinion, which will not either bear the light of chemical or mineral investigation. The subject of these chalk flints will be minutely examined in its proper place.
Our author has carefully examined the subject of flintification; and the country where he makes his observations would seem to be well disposed for such a research. He has had great opportunity and inclination to examine the subject which he writes upon; and he has given a distinct account of what be has seen. His description of the flintification of sand-stone is extremely interesting. I will therefore transcribe it, both as a valuable portion of natural history, and also in order to contrast this author’s opinion, with regard to the means employed by nature in petrifying bodies, and that which I maintain to be the general consolidating operation of the globe. It is Section V. _Generation du Caillou du Silex du Gres, ou Pierre Sablonneuse_.
“Tout gres est susceptible de cette metamorphose quant au grain et quant a la couleur; depuis la breccia quartzeuse jusqu’a la pierre a rasoir; et depuis le gres blanc jusqu’au brun et presque noiratre, tient ou non tient, dur, ou presque friable, c’est indifferent, toutes ces varietes donnent du silex, et surtout de la calcedoine, de la cornaline, et des agathes. Quant au ciment je l’y ai toujours remarque calcaire et faisant effervescence avec les acides dans les endroits de la pierre qui n’etoient point encore changes; et jamais je n’ai vu ce changement dans du gres dont le ciment fut ou quartzeux ou argileux et refractaire. Ainsi le ciment entre pour quelque chose dans ce changement.
“Le commencement de cette metamorphose paroit (autant que j’ai pu l’observer dans mes debris roules) se faire par le ciment, qui dissout la, ou les agens eurent l’acces libre, rend les grains en quartz mobiles, les emporte, les mele avec sa masse dense-liquide, les dissout, meme en partie, et forme, dans cet etat, des veines et de masses calcedonieuse, carneoliques, ou d’une autre espece de silex, au milieu du gres peu, ou pas du tout, change. Car autant que je puis voir, ce n’est pas par couches ou veines qu’elle s’opere, mais par boules et masses rond-oblongues. Au commencement ces veines et taches sont fort minces, et le reste du gres n’est point du tout, ou a peine sensiblement change hormis qu’il gagne, plus de consistence, a proportion du changement souffert. Mais a mesure que le silex y augmente et se perfectionne, on y appercoit les degres par lesquels a passe cette operation. Les nuance du passage d’une pierre a l’autre deviennent plus visibles, les veines et masses de silex grandissent au point, meme, qu’il y a jusqu’aux trois quart du gres change en silex clair comme de l’eau n’ayant que fort peu de grains de sable nageants dans sa masse. Des morceaux de cette espece sont rares a la verite, mais j’en ai, cependant, trouve quelques uns. Ordinairement, dans les beaux morceaux, le silex fait la base, et le sable y est, comme nageant tantot en grains separes tantot en parties et flocons. Dans les pieces moins belles, le sable fait la base, et le silex sert a la fois de ciment, et forme aussi plus ou moins de veines, qui traversent la masse en maintes et maintes directions. Mais si c’est un gres a gros grains, ou de la breccia, alors le reste prend la nature silicieuse mele de sable fin, et les gros grains de quartz restent tels, qu’ils etoient, sans changer. J’ai deja remarque que cette metamorphose semble s’operer, comme celle des cailloux d’origine calcaire en forme approchans la spherique, il faut encore y a jouter, que j’ai lieu de croire, qu’elle se fasse aussi du dedans en dehors, tout, comme la decomposition se fait du dehors au dedans.
“Il arrive dans cette pierre, comme dans toute autre, qu’il se forme des crystallisations dans les cavites. Lorsqu’elles sont de silex, leur figure est toujours mamelonnee, mais leur eau ou purete, leur grandeur et leur couleur n’est pas par tout egale. Il y en a qui sont grands, et de la plus pure calcedoine, d’autres sont petits et chaque goutte ou mamelon contient un grain de sable, de facon que cela a l’air d’un gres crystallise en mamelons ou stalagmitique. D’autres encore sont, de calcedoine, mais recouverts d’une croute, tantot blanche qui fait effervescence avec l’acide mineral, et qui est, par consequent, de nature calcaire; tantot cette croute est bleue foncee nuancee de bleu-celeste; tantot, enfin, elle est noire, mais toutes les deux refractaires. Outre ces crystallisations silicieuses, il y en a, quoique rarement, de quartzeuses, qui ou forment de petites veines de crystal, ou bien des groupes de crystaux quartzeux, ou qui enfin, enduisent les mamelons de silex.”
Our author then makes a specification of the different varieties; after which he continues, p. 69.
“Apres tout ceci, l’on conviendra j’espere, que notre grais est une pierre bien singuliere, et surpassant, a bien des egards, le grais, faussement dit crystallise, de Fontainebleau. La raison de la figure du grais Francois est fort evidente, c’est le spath calcaire, qui lui sert de ciment, qui la lui fit prendre; mais qu’est-ce qui opere les metamorphoses racontees dans notre grais siliceux? Seroit-ce son ciment calcaire ou marneux par les memes raisons, qui font changer la marne en silex? La chose est tres-probable, et je n’en saurois pas meme, deviner d’autre. En ce cas la nature auroit un moyen d’operer par la voie humide, ce que nous faisons dans nos laboratoires en quelque facon, par la voie seche, c, a, d, de fondre et liquefier la terre vitrescible, au moyen des alcalis; secret que nous lui avons deja arrache en partie, en faisant la liqueur silicieuse.”
“Je n’ose, cependant, decider pas meme hypothetiquement, sur cette matiere, pour n’avoir pu observer la nature dans ses ateliers, et parce que je ne possede que des pieces, qui detachees de leur lieu natal, depuis un tres long-tems, furent exposees aux intemperies des saisons, ou elles peuvent avoir souffert bien de changemens.”
There cannot be a more fair exposition of facts; and it is only our author’s opinion of this mineral transmutation that I would controvert. I do not pretend to understand the manner of operating that our author here supposes nature to take. I only maintain, that here, as every where in general, the loose and incoherent strata of the globe have been petrified, that is, consolidated, by means of the fusion of their substances; and this I think is confirmed from the accurate description here given of the flintification of sand-stone. Here is described very distinctly an appearance which is very common or general on those occasions; this is the parts or particles of stone floating in the fluid siliceous substance, and there dissolving more or less.
M. de Carosi describes very systematically the generation of silex, calcedony, onyx, and quartz, in calcareous earth, marl, gypsum, sand-stone, and also what he terms _terre glaise, ou de l’Argile_. It is in this last that we find a perfect analogy with what is so frequent in this country of Scotland. These are the agates, calcedonies, calcareous and zeolite nodules, which are found produced in our whin-stone or subterraneous lavas, that is, the amygdaloides of Crondstedt. Naturalists explain the formation of those nodular bodies differently. The Chevalier de Dolomieu supposes these rocks to have been erupted lavas, originally containing cavities; and that these cavities in the solid rock had been afterwards filled and crystallised, by means of infiltration, with the different substances which are found variously concreted and crystallised within the solid rocks. Our author, on the contrary, supposes these formed by a species of chemical transmutation of calcareous and argillaceous earths, which, if not altogether incomprehensible, is at least not in any degree, so far as I know, a thing to be understood.
This is not the place where that subject of these particular rocks, which is extremely interesting, is to be examined. We shall afterwards have occasion to treat of that matter at large. It is sufficient here to observe, that our author finds occasion to generalise the formation of those petrifactions with the flintifications in calcareous and gypseous bodies. When, therefore, the formation of any of them shall be demonstrated, as having taken its origin in the fusion of those substances, this mode of operation, which is generalised in the consolidation of strata, will be properly inferred in all the rest.
Petrifaction is a subject in which mineralogists have perhaps wandered more widely from the truth than in any other part of natural history; and the reason is plain. The mineral operations of nature lie in a part of the globe which is necessarily inaccessible to man, and where the powers of nature act under very different conditions from those which we find take place in the only situation where we can live. Naturalists, therefore, finding in stalactical incrustation a cause for the formation of stone, in many respects analogous to what is found in the strata of the earth, and which had come from the mineral region in a consolidated state, have, without due consideration, attributed to this cause all the appearances of petrifaction or mineral concretion. It has been one of the objects of this work to show that this operation of incrustation, or petrifaction by means of solution, is altogether ineffectual for producing mineral concretions; and that, even were it capable of forming those mineral bodies, yet that, in the solid parts of this earth, formed by a deposit of travelled materials at the bottom of the sea, the conditions necessary to this incrustating process do not take place.
Those enlightened naturalists who have of late been employed in carefully examining the evidences of mineral operations, are often staggered in finding appearances inconsistent with the received doctrine of infiltration; they then have recourse to ingenious suppositions, in order to explain that enigma. In giving examples of this kind. I have in view both to represent the natural history these mineralists furnish us with, which is extremely interesting, and also to show the various shapes in which error will proceed, when ingenious men are obliged to reason without some necessary principle in their science. We have just now had an example in Europe; I will next present the reader with one from Asia.
M. Patrin, in his _Notice Mineralogique de la Daourie_, (Journal de Physique, Mars 1791) gives us a very distinct account of what he met with in that region. Describing the country of Doutchersk upon the river Argun, in Siberia, he proceeds thus:
“Ces colines sont formees d’un hornstein gris qui paroit se convertir en pierre calcaire par l’action des meteores; car tout celui qu’on prend hors du contact de l’air donne les plus vives etincelles, et ne fait pas la moindre effervescence avec les acides, meme apres avoir ete calcine; et l’on observe celui qui est a decouvert, passer, par nuances insensibles, jusqu’a l’etat de pierre calcaire parfaite de couleur blanchatre.”
Here M. Patrin has persuaded himself, probably from an imperfect examination of the subject, that there takes place a mineral metamorphosis, which certainly is not found in any other part of the earth, and for which he does not find any particular cause. The natural effect of the meteors, in other parts of the earth, is to dissolve the calcareous substance out of bodies exposed to those agents; and the gradation from the one of those two things to the other, which seems to be the data on which he had proceeded in forming his conclusion, is not sufficient to prove the metamorphosis, even were there not so strong a physical objection to it; for, it is by no means unusual for mineral bodies to graduate thus from one substance to another. However that be, this is not the principal object of the example[42].
[Note 42: Here we have well informed naturalists reasoning with all the light of our present mineralogy, and maintaining, on the one hand, that gypsum is transformed into calcedony, by the operation of the meteors, or some such cause; and, on the other, that a siliceous substance is by the same means converted into lime-stone. What should we now conclude from this?–That calcareous and siliceous substances were mutually convertible. But then this is only in certain districts of Poland and Siberia. Every where, indeed, we find strange mixtures of calcareous and siliceous bodies; but neither mineralists nor chemists have, from these examples, ventured to affirm a metamorphosis, which might have spared them much difficulty in explaining those appearances.
This is a subject that may be taken in very different lights. In one view, no doubt, there would appear to be absurdity in the doctrine of metamorphosis, as there is now a days acknowledged to be in that of _lusus naturae_; and those reasoning mineralists might thus, in the opinion of some philosophers, expose their theory to contempt and ridicule. This is not the light in which I view the subject. I give those gentlemen credit for diligently observing nature; and I applaud them for having the merit to reason for themselves, which would seem to be the case with few of the many naturalists who now speak and write upon the subject.
Let us now draw an inference, with regard to this, in judging of the different theories. Either the received system concerning mineral operations is just, in which case those gentlemen, who employ a secret metamorphosis, may be to blame in laying it aside; or it is erroneous and deficient; and, in that case, they have the merit of distinguishing the error or deficiency of the prevailing system. How far they have seen the system of nature, in those examples which they have described, is another question. In the mean time, I am to avail myself of the testimony of those gentlemen of observation, by which the insufficiency at least of the received mineral system is acknowledged.]
After speculating upon the effect of the ancient ocean upon the mountains of that country, he proceeds as follows:
“Je laisse ces conjectures pour remarquer un fait singulier: la colline, qui est au nord de l’eglise de la fonderie, a son arrete composee de ce hornstein qui se decompose en pierre calcaire; mais ici, les parties, qui sont ainsi decomposees, offrent une substance calcedonieuse disposees par zones concentriques, comme on l’observe dans les agates d’oberstein; mais ce ne sont point ici des corps parasites formes par infiltration dans des cavites pre-existantes comme les agates; on voit que ce sont les parties constituantes de la roche qui, _par un travail interne_, et par une sorte de crystallisation, out pris cette disposition reguliere (que ce mot de _crystallisation_ ne revolte point, j’appelle ainsi toute tendance a prendre une forme constante, polyedre ou non polyedre.) Les couches les plus voisine du centre sont nettes et distinctes; peu-a-peu elles le sont moins, et enfin elles s’evanouissent et se confondent avec le fond de la roche. Chaque assemblage de ces zones a une forme ronde ou ovale plus ou moins reguliere de sept a huit pouces de diametre.
“Cela ressemble en grand a ce qu’on observe dans les pierres oeillees, et la cause est vraisemblablement la meme. Je le repete, je regarde cette disposition reguliere comme une veritable cristallisation, qui peut s’operer et qui s’opere en effet dans l’interieur des corp les plus solide, tant qu’ils sont fournis a l’action des agens de la nature.
“Tous ceux qui visitent l’interieur de la terre savent que les roches memes le plus compactes y sont intimement penetrees d’humidite, et ce fluide n’est certainement pas l’eau pure; c’est l’agent qui opere toutes les agregations, toutes les cristallisations, tous les travaux de la nature dans le regne mineral. On peut donc aisement concevoir qu’a la faveur de ce fluide, il regne, dans les parties les plus intimes des