Chapter VIII: Section III (2)

As another excellence of this theory, I may, perhaps, be allowed to remark, that it extends its consequences beyond those to which the author of it has himself adverted, and that it affords, which no geological theory has yet done, a satisfactory explanation of the spheroidal figure of the earth.[40]

[Footnote 40: NOTE XXV.]

133. Yet, with all these circumstances of originality, grandeur, and simplicity in its favour, with the addition of evidence as demonstrative as the nature of the subject will admit, this theory has probably many obstacles to overcome, before it meet the general approbation. The greatness of the objects which it sets before us, alarms the imagination; the powers which it supposes to be lodged in the subterraneous regions; a heat which has subdued the most refractory rocks, and has melted beds of marble and quartz; an expansive force, which has folded up, or broken the strata, and raised whole continents from the bottom of the sea; these are things with which, however certainly they may be proved, the mind cannot soon be familiarized. The change and movement also, which this theory ascribes to all that the senses declare to be most unalterable, raise up against it the same prejudices which formerly opposed the belief in the true system of the world; and it affords a curious proof, how little such prejudices are subject to vary, that as Aristarchus, an ancient follower of that system, was charged with impiety for moving the everlasting Vesta from her place, so Dr Hutton, nearly on the same ground, has been subjected to the very same accusation. Even the length of time which this theory regards as necessary to the revolutions of the globe, is looked on as belonging to the marvellous; and man, who finds himself constrained by the want of time, or of space, in almost all his undertakings, forgets, that in these, if in any thing, the riches of nature reject all limitation.[41]

[Footnote 41: NOTE XXVI.]

The evidence which must be opposed to all these causes of incredulity, cannot be fully understood without much study and attention. It requires not only a careful examination of particular instances, but comprehensive views of the whole phenomena of geology; the comparison of things very remote with one another; the interpretation of the _obscure_ by the _luminous_, and of the _doubtful_ by the _decisive_ appearances. The geologist must not content himself with examining the insulated specimens of his cabinet, or with pursuing the nice subtleties of mineralogical arrangement; he must study the relations of fossils, as they actually exist; he must follow nature into her wildest and most inaccessible abodes; and must select, for the places of his observations, those points, from which the variety and gradation of her works can be most extensively and accurately explored. Without such an exact and comprehensive survey, his mind will hardly be prepared to relish the true theory of the earth. "_Naturæ enim vis atque majestas omnibus momentis fide caret, si quis modo partes atque non totam complectatur animo_".[42]

[Footnote 42: PLIN. Hist. Nat. lib. vii. Cap. i.]

134. If indeed this theory of the earth is as well founded as we suppose it to be, the lapse of time must necessarily remove all objections to it, and the progress of science will only develope its evidence more fully. As it stands at present, though true, it must be still imperfect; and it cannot be doubted, that the great principles of it, though established on an immoveable basis, must yet undergo many modifications, requiring to be limited, in one place, or to be extended, in another. A work of such variety and extent cannot be carried to perfection by the efforts of an individual. Ages may be required to fill up the bold outline which Dr Hutton has traced with so masterly a hand; to detach the parts more completely from the general mass; to adjust the size and position of the subordinate members; and to give to the whole piece the exact proportion and true colouring of nature.

This, however, in length of time, may be expected from the advancement of science, and from the mutual assistance which parts of knowledge, seemingly the most remote, often afford to one another. Not only may the observations of the mineralogist, in tracts yet unexplored, complete the enumeration of geological facts; and the experiments of the chemist, on substances not yet subjected to his analysis, afford a more intimate acquaintance with the nature of fossils, and a measure of the power of those chemical agents to which this theory ascribes such vast effects: but also, from other sciences, less directly connected with the natural history of the earth, much information may be received. The accurate geographical maps and surveys which are now making; the foundings; the obsevations of currents; the barometrical measurements, may all combine to ascertain the reality, and to fix the quantity of those changes which terrestrial bodies continually undergo. Every new improvement in science affords the means of delineating more accurately the face of nature as it now exists, and of transmitting, to future ages, an account, which may be compared with the face of nature as it shall then exist. If, therefore, the science of the present times is destined to survive the physical revolutions of the globe, the HUTTONIAN THEORY may be confirmed by historical record; and the author of it will be remembered among the illustrious few, whose systems have been verified by the observations of succeeding ages, supported by facts unknown to themselves, and established by the decisions of a tribunal, slow, but infallible, in distinguishing between truth and falsehood.

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NOTES AND ADDITIONS.

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NOTES AND ADDITIONS.

NOTE I. § 2.

_Origin of calcareous rocks._

135. IT has been asserted, that Dr Hutton went farther than is stated at § 2, and maintained all calcareous matter to be _originally_ of animal formation. This position, however, is so far from being laid down by Dr Hutton, that it belongs to an inquiry which he carefully avoided to enter on, as being altogether beyond the limits of philosophical investigation.

He has indeed no where treated of the _first origin_ of any of the earths, or of any substance whatsoever, but only of the transformations which bodies have undergone since the present laws of nature were established. He considered this last as all that a science, built on experiment and observation, can possibly extend to; and willingly left, to more presumptuous inquirers, the task of carrying their reasonings beyond the boundaries of nature, and of unfolding the properties of the chaotic fluid, with as much minuteness of detail, as if they were describing the circumstances of a chemical process which they had actually witnessed.

The idea of calcareous matter which really belongs to the Huttonian Theory, is, that in all the changes which the terraqueous globe has undergone in past ages, this matter existed, as it does now, either in the form of limestone and marble, or in the composition of other stones, or in the state of corals, shells, and bones of animals. It may be true, that there is no particle of calcareous matter, at present existing on the surface of the earth, that has not, at some time, made a part of an animal body; but of this we can have no certainty, nor is it of any importance that we should. It is enough to know, that the rocks of marble and limestone contain in general marks of having been formed from materials collected at the bottom of the sea; and of this a single cockle-shell, or piece of coral, found included in a rock, is a sufficient proof with respect to the whole mass of which it makes a part.

The principal object which Dr Hutton had in view when he spoke of the masses of marble and limestone, as composed of the calcareous matter of marine bodies,[43] was to prove, that they had been all formed at the bottom of the sea, and from materials there deposited. His general conclusion is, "That all the strata of the earth, not only those consisting of such calcareous masses, but others superincumbent upon these, have had their origin at the bottom of the sea, by the collection of sand and gravel, of shells, of coralline and crustaceous bodies, and of earths and clays variously mixed, or separated and accumulated. This is a general conclusion, well authenticated by the appearances of nature, and highly important in the natural history of the earth."[44]

[Footnote 43: Theory of the Earth, vol. i. p. 23, 24.]

[Footnote 44: Theory of the Earth, vol. i. p. 26.]

136. In his Geological Essays, Mr Kirwan says, that "some geologists, as Buffon, and of late Dr Hutton, have excluded calcareous earth from the number of the primeval, asserting the masses of it we at present behold to proceed from shell-fish. But, in addition to the unfounded supposition, that shell-fish, or any animals, possess the power of producing any simple earth, these philosophers should have considered, that, before the existence of any fish, the stony masses that inclose the bason of the sea, must have existed; and, among these, there is none in which calcareous earth is not found. Dr Hutton endeavours to _evade_ this argument, by supposing the world we now inhabit to have arisen from the ruins and fragments of an anterior, without pointing at any original. If we are thus to proceed _in infinitum_, I shall not pretend to follow him; but, if he stops any where, he will find the same argument equally to occur."[45]

[Footnote 45: Geol. Essays, p. 13.]

The argument here employed would certainly be conclusive against any one, who, in disputing about the _first origin_ of things, should deny that the calcareous is as ancient as any other of the simple earths. But this has nothing to do with Dr Hutton's speculations, which, as has been just said, never extended to the _first origin_ of substances, but were confined entirely to their changes; so that what he asserts concerning the calcareous rocks, is no more than that those which we now see have been formed from loose materials, deposited at the bottom of the sea. It was not therefore in order to _evade_ Mr Kirwan's argument, as the preceding passage would lead us to believe, that he supposed the world which we now inhabit to have arisen from the ruin and waste of an anterior world; but it was because this seemed to him a conclusion which necessarily followed from the phenomena of geology, and it was a conclusion that he had deduced long before he heard of Mr Kirwan's objections to his system. Instead of an _evasion_, therefore, any one who considers the subject fairly, will see, in Dr Hutton's reasoning, nothing but the caution of a philosopher, who wisely confines his theory within the same limits by which nature has confined his experience and observation.

It is nevertheless true, that Dr Hutton has sometimes expressed himself as if he thought that the present calcareous rocks are all composed of animal remains.[46] This conclusion, however, is more general than the facts warrant; and, from some incorrectness or ambiguity of language, is certainly more general than he intended. The idea of calcareous rocks, on which he argues throughout his whole theory, is precisely that which is stated in the preceding article.

[Footnote 46: Theory of the Earth, vol. i. p. 23.]

NOTE II. § 6.

_Origin of coal._

137. The vegetable origin of coal seems to be sufficiently proved by the reasoning in § 5. and 6.; and that reasoning will appear still more satisfactory, from what is said at § 28. and 29., concerning the consolidation of this fossil. Dr Hutton has treated both of the matter of coal and of its consolidation. Part. I. Chap. 8., of his Theory of the Earth [47].

[Footnote 47: Vol. i. p. 558, &c.]

The notion, however, that coal is of vegetable origin, is not peculiar to this theory, but has been for some time the prevailing opinion. Buffon supposes this mineral to be formed from vegetable and animal substances, the oil and fat of which have been converted into bitumen by the action of acids.[48] A fundamental mistake, however, is committed by this author, and by M. GENSANNE, (author of the natural history of Languedoc,) on whose observations he greatly relies, in considering coal as consisting of bitumen united to earth, thus omitting the only ingredient essential to coal, namely the carbon or charcoal. This may truly be considered as the essential part, because coal may exist without bitumen, as in the instance of blind coal, but not without charcoal.

[Footnote 48: Hist. Nat. des Mineraux. tom. i. p. 429, 4to edit.]

Another theory of coal, very analogous to Dr Hutton's, is that of ARDUINO, professor of mineralogy at Venice, in which he supposes it formed from vegetable and animal remains from the land and sea, but chiefly from the latter.[49] This theory of coal is contained in Dr Hutton's, in which the animal and vegetable remains must be supposed to come both from the earth and the sea. It seems to be without any good reason that Arduino considers the sea as the chief source of these materials. His remarks, however, are very ingenious, and deserving of attention.

[Footnote 49: Saggio Fisico-mineralogico del Sig. Giov. Arduino; Atti di Siena, tom. v. p. 228, 281, &c.]

These accounts of the origin of coal are all nearly the same; it is in what relates to the distinction between the common coal, in which there is no ligneous structure, and those varieties of it in which that structure is apparent, and again in explaining the consolidation of both, that the theory laid down here is peculiar.

138. Some other mineralogists refer one of the ingredients of coal to the vegetable kingdom, but not the other. Unable to resist the conviction which arises from the fibrous structure of parts of strata, and even entire strata of coal, they have supposed, that wood, which had been somehow buried in the earth, or perhaps deposited at the bottom of the sea, had become impregnated with bitumen, which last, however, they consider as of mineral origin. This appears to be the opinion of Lehman; and also of some very late writers. There seems, however, to be hardly less reason for referring the origin of one part of coal to the vegetable or animal kingdom than another. The two last are certainly capable of furnishing both the carbonic and bituminous parts; and therefore, to derive these from different sources, is at least a very unnecessary complication of hypotheses.

139. Another explanation of coal, very different from any of the preceding, has lately been advanced and set up in opposition to the Huttonian Theory. Mr Kirwan,[50] the only mineralogist, I believe, who has attempted to derive both the carbonic and bituminous matter of coal from the mineral kingdom, distinguishes between wood coal and mineral coal, and gives a theory entirely new of the formation of the latter. Wood coal is that in which the ligneous structure is so apparent, as to leave no doubt of its vegetable origin; mineral coal is that in which no such structure can be discovered, and is the same which Dr Hutton derives from the vegetable juices, and other remains, comminuted, dispersed, carried into the sea, and there precipitated, so as to unite with different proportions of earth, and to become afterwards mineralized.

[Footnote 50: Geol. Essays, essay vii. p. 290.]

These two species of coal, which the Huttonian theory considers as gradations of the same substance, Mr Kirwan regards as perfectly distinct, constituting two minerals, of an origin and formation entirely different. He therefore endeavours to ascertain the distinguishing characters of each, considered geologically.

140. But here the leading distinction, implied in all the rest, that the two kinds of coal are never found in the same bed, but always in different situations, and with different laws of stratification, is expressly contradicted by matter of fact. Coal, as is said above, with its ligneous texture quite apparent, and coal with no such structure visible, are often found in the same seam, are brought up from the same mine, and united in the same specimen. I have a specimen from a bed of coal, in the Isle of Sky, found under a basaltic rock, consisting of a ligneous part, which graduates into one in which there is no vestige of a fibrous texture, and in which the surface is smooth and glossy, with a fracture almost vitreous. The upper part of the specimen is therefore perfect wood coal, and the under part perfect mineral-coal, in the language of Mr Kirwan; at the same time that the transition from the one to the other is made by insensible degrees. This specimen, were it perfectly solitary, is sufficient to prove the identity of the two species of coal we are now speaking of, and to show, that the difference between them is accidental, not essential. The specimen, however, is far from being solitary; the number of similar appearances is so great, as hardly to have escaped the observation of any mineralogist. Mr Kirwan admits, that wood coal is often found under basaltes;[51] but what is essential to be remarked is, that, in this instance, we have both the wood coal and the common mineral-coal, lying under that rock, and the one passing gradually into the other It appears, indeed, that many of the facts which Mr Kirwan produces, in treating of what he calls _carboniferous_ soils, are quite inconsistent with the distinction he would make between wood-coal and mineral coal.[52]

[Footnote 51: Geol. Essays, p. 310.]

[Footnote 52: _Ibid._ p. 311.]

141. It is, however, true, that there are instances in which the wood coal, or fossil wood, as it is usually called, forms entire beds, quite unconnected with the ordinary coal, and stratified in some respects differently. Such is the Bovey coal in Devonshire, the wood-coal in the north of Ireland, and perhaps the Surturbrandt of Iceland. With respect to the Bovey coal, it does by no means answer to one of Mr Kirwan's remarks, viz. that late observations have ascertained, that no such parallelism of the beds, as in mineral coal, nor even any distinct number of strata is found. In the Bovey coal, the number of strata is very well defined, by beds of clay regularly interposed; but as to the extent of these beds, the coal having been worked only at one place, and by an open pit, without any extensive subterraneous excavation, nothing is known with certainty.

In the Bovey coal too, I must observe, though its beds have the ligneous structure very distinct, the clay interposed between these beds, which is but little indurated, contains a great deal of coaly matter, in the form of thin flakes, interspersed through it. So far as I know, there are no mineral reins nor shifts, nor any bed of indurated stone, that accompany this coal; so that, though one can not doubt of its vegetable origin, some doubt may be entertained concerning the nature of the mineralizing operations, to which it has been subjected The consideration of these, however, does not belong to the present argument; and the peculiarities of this semi-mineralized coal, as it may be called, have nothing to do with the general question, whether wood coal and mineral coal are the same substance; about which question, if the gradations are properly considered, I think, no reasonable doubt can remain.

142. One of Mr Kirwan's objections to the vegetable origin of coal, is founded on this fact, that there is, in the museum at Florence, a cellular sandstone, the cells of which are filled with genuine mineral coal. "Could this (adds he) have been originally wood?"[53] The answer to the interrogatory proposed here as a _reductio ad absurdum_, is, that most undoubtedly it may have been wood. Sandstone with charred wood, that is, with wood coal in it, is not an uncommon phenomenon in coal countries. I have seen a specimen of this kind from the Hales Quarry, near Edinburgh, consisting of a piece of charred wood, imbedded in sandstone; the wood was much altered, but the remains of its fibrous structure were distinctly visible. This affords a perfect commentary on the specimen in the Florence cabinet.

[Footnote 53: Geol. Essays, p. 321.]

143. If then it be granted, as I think it must, that the two kinds of coal we have been speaking of are of the same origin, it is not very necessary to enter on a refutation of Mr Kirwan's theory with respect to either of them. His account of the formation of mineral coal, however, is so singular, that it cannot be passed over without remark.

Mr Kirwan supposes, 1mo, That natural carbon was originally contained in many mountains of the granite and porphyritic order, and also in siliceous schistus; and might, by disintegration and decomposition, be separated from the stony particles. 2do, That both petrol and carbon are often contained in trap, since hornblende, which has lately been found to contain carbon, very frequently enters into its composition.

"My opinion (adds he) is, that coal mines, or strata of coal, as well as the mountains in which they are found, owe their origin to the disintegration of primeval mountains, either now totally destroyed, or whose height and bulk, in consequence of such disintegration, are considerably lessened; and that these rocks, anciently destroyed, contained most probably a far larger proportion of carbon and petrol than those of the same denomination now contain, since their disintegration took place at so early a period.[54]

[Footnote 54: Geol. Essays, p. 328, &c.]

"By the decomposition of these mountains, the feldspar and hornblende were converted into clay; the bituminous particles, thus set free, reunited, and were absorbed, partly by the argil, but chiefly by the carbonaceous matter, with which they have the greatest affinity. The carbonic and bituminous particles, thus united, being difficultly miscible with water, and specifically heavier, sunk through the moist, pulpy, incoherent argillaceous masses, and formed the lowest stratum," &c.

Such is Mr Kirwan's theory of the formation of coal, and nobody I think will dispute the originality of it.

144. To enter on a formal refutation of an opinion so loaded with objections, would be a task as irksome as unnecessary. A few observations will suffice.

The notion of the great degradation of mountains, involved in this hypothesis, is the part of it to which I am least disposed to object. But I cannot help reminding Mr Kirwan, that the effects of waste are not supposed less in this, than in Dr Hutton's theory; and that he has assumed the very principle, of which that theory makes so much use, though he has reserved to himself, as it should seem, the right of denying it, when it does not accord with his system. It is indeed worth while to compare what is said concerning the degradation of mountains, in the above quotations, and still more fully in the book itself, with what is advanced concerning their indestructibility, in another passage of the same volume:[55]

[Footnote 55: Page 436.]

"All mountains are not subject to decay; for instance, scarce any of those that consist of red granite. The stone of which the Runic rocks are formed, have withstood decomposition for two thousand years, as their characters evince," &c.

"Basaltic pillars, in general, bid defiance to decay," &c. He goes on to deny every step of the degradation of land, by which it is wasted, carried into the sea, and spread out over its bottom, though all these are necessary _postulata_ in his theory of the formation of coal. One can be at no loss about estimating the value of a system, in which such gross inconsistencies make a necessary part.

145. The quantity of hornblende and siliceous schistus, necessary to be decomposed, in order to produce the coal strata presently existing, is enormous, and would lead to an estimate of what is worn away from the primeval mountains, far exceeding any thing that Dr Hutton has supposed. It is true, that Mr Kirwan, never at all embarrassed about preserving a similitude between nature as she is now, and as she was heretofore, lays it down, that the part of the primeval mountains which is worn away, contained much more carbon than the part which is left behind. This, however, is an arbitrary supposition; and since, in this system, such suppositions are so easily admitted, why may we not conceive, in the primeval mountains, a more copious source of carbonic matter than hornblende or siliceous schistus? We have but to imagine, that the _diamond_ existed among these mountains in such abundance, as to constitute large rocks. This stone being made up of pure, or highly concentrated carbon, the adamantine summits of a single ridge, by their decomposition, might afford a carbonic basis, sufficient for the coal beds of all the surrounding plains.

146. We may also object to Mr Kirwan, that the siliceous part of the mountains has not been chemically dissolved; it has been only abraded and worn away. Mechanical action has reduced the quartz to gravel and sand, but has not produced on it any chemical change. The carbon, therefore, could not be let loose. Experiment, indeed, might be employed, to determine whether the siliceous matter of the secondary, and of the primary strata contains this substance in the same proportion.

Again, a more fatal symptom can hardly be imagined in any theory, than that, when the circumstances of the phenomena to be explained are _a little_ changed, the theory is under the necessity of changing _a great deal_. Now, this is what happens to Mr Kirwan's theory, in the attempt made to explain by it the stratum of coal described in the _Annales de Chimie_,[56] as cutting a mountain of argillaceous strata in two, at about three-fourths of its height. This stratum, Mr Kirwan says, must have been formed by _transudation_ from the superior part of the mountain,[57] Besides that this is a gratuitous supposition of a thing, without example, it involves in it an absurdity, which becomes evident the moment the question is asked, What occupied the place of the coal-bed before the transudation from the upper part of the mountain? Has the _liquid coal_, as it percolated through the upper strata, expelled any substance from the place it now occupies? or has it been powerful enough to raise up, or to float, as it were, the upper part of the mountain?

[Footnote 56: Tom. xi. p. 272.]

[Footnote 57: Geol. Essays, p. 338.]

The situation of this bed of coal is not singular, and its formation is easily explained on Dr Hutton's theory. It is part of a stratum of coal, which has been deposited, like all others, at the bottom of the sea; from whence certain causes, of very general operation, have raised it up, together with the attending strata: these strata have since been all cut down, and worn away by the operations of the surface; and the mountain, with the coal stratum in the middle of it, is a part of them which has been left behind. There is no wonder, that a coal stratum should be found alternating with others, in a mountain, any more than in the bowels of the earth, and no more need of a separate explanation.[58]

[Footnote 58: This stratum of coal, which is described by HASSENFRATZ, is remarkable for being in a mountain which rests immediately on primary schistus and granite.]

147. After all, it may be asked, for what purpose is it that so many incongruous and ill supported hypotheses are thus piled on one another? is it only to avoid ascribing the carbonic and bituminous matter of coal to a substance in which we know with certainty that such matter resides in great abundance, in order to derive it from other substances, in which a subtle analysis has shown, that it exists in a very small proportion? Such reasoning is so great a trespass on every principle of common sense, not to say of sound philosophy, that, to bestow any time on the refutation of it, is, in some degree, to fall under the same censure.

NOTE III. § 7.

_Primitive mountains._

148. The enumeration of the different kinds of primary schistus, at § 7, is not proposed as at all complete. It will be less defective, however, if we add to it _talcose schistus_, and _lapis ollaris_ or _potstone_.[59]

[Footnote 59: Kirwan's Mineralogy, vol. i. p. 155.]

149. The rocks called here by the name of primary, were first distinguished, as forming the basis of all the great chains of mountains, and as constituting a separate division of the mineral kingdom, by J. G. LEHMAN, director of the Prussian mines. See his work, intituled, _Essai d'une Histoire Naturelle des Couches de la Terre_.[60] These rocks were regarded by Lehman as parts of the original nucleus of the globe, which had undergone no alteration, but remained now such as they were at first created; and, agreeably to this supposition, he bestowed on them, and on the mountains composed of them, the name of primitive. He remarks, nevertheless, their distribution into beds, either perpendicular to the horizon, or highly inclined, and the super-position of the secondary and horizontal strata. However mineralogists may now differ in their theories from Lehman, they must consider this distinction as a great step in the science of geology, and very material to the right arrangement of the natural history of the earth.

[Footnote 60: Tom. iii. p. 239, &c. The French translation is in 1759, but the original preface is dated at Berlin, 1756.]

150. Several mineralogists have agreed with him in the supposition, that these rocks are a part of the original structure of the globe, and prior to all organized matter. Of this number is PALLAS;[61] and also DE LUC, who applies the term _primordial_ to the rocks in question, and considers them as neither stratified nor formed by water.[62] In his subsequent writings, however, he admits their formation from aqueous deposition, as the Neptunists do in general, but holds them to be more ancient than organized bodies.

[Footnote 61: Observations sur la Formation des Montagnes.]

[Footnote 62: Lettres Phys. Sur l'Histoire de la Terre, tom. ii. p. 206.]

151. PINI, professor of natural history at Milan, has denied the stratification of primitive mountains, in a memoir on the mineralogy of St Gothard, and in another on the revolutions of the globe.[63] His reasonings are opposed by SAUSSURE,[64] and are certainly, in many respects, very open to attack. They proceed on a comparison between the division of rocks, by what is called the planes of their stratification, and their division by transverse fissures: two things, which he thinks so much alike, that they ought not to be referred to different causes; and, as the one cannot be regarded as the effect of aqueous deposition, so neither should the other. This is a very fallacious argument, because it confounds two things that are essentially different; and, instead of inquiring about a matter of fact, inquires about its cause. The truth is, that the dispute has arisen from not distinguishing the granite from the schistus mountains, and from involving both under the name of primitive. M. Pini seems to be in the right, when he holds the granite of St Gothard to be unstratified; but it is without any good reason, that he would extend the same conclusion to the schistus of that mountain. CHARPENTIER, and Saussure, in his last two volumes, contend even for the stratification of granite.[65]

[Footnote 63: Memoria sulle Rivoluzioni del Globo Terrestre; Memorie della Societa Italiana, tom. v. p. 222, &c.]

[Footnote 64: Voyages aux Alpes, tom. iv. § 1881.]

[Footnote 65: See NOTE XV. on Granite.]

As the consent, if not universal, is very general for the stratification of the primary schistus, and the fact itself abundantly obvious, in almost all the instances I have ever met with, I have not considered it as necessary to enter here into any argument on this subject.

NOTE IV. § 8.

_Primary strata not primitive._

152. An account of the facts referred to § 8, may be found in Hutton's Theory, vol. i. p. 332, &c. To what is there said, of the shells contained in the primary limestone of Cumberland, I must add, that I have since had an opportunity of verifying the conjecture, that the limestone rock, in which the shells were found, near the head of _Coniston_ Lake, is part of the same body of strata, where shells were found, in a quarry between Ambleside and Low-wood. The limestone of that quarry contains several marine objects; it is in strata declining about 10° from the perpendicular, toward the S. E., and forms a belt, stretching across the country from N. E. to S. W.

In a quarry where the argillaceous schistus, on the south side of this limestone belt, is worked for pavement, are impressions of what I think may safely be accounted marine objects; they have the form of shells, are much indurated, and full of pyrites. They seem to be of the same kind with the impressions said to be found in a slate quarry, near the village of Mat in Switzerland.[66]

[Footnote 66: Hutton's Theory, vol. i. p. 327.]

Another spot, affording instances of shells in primary limestone, is in Devonshire. On the sea shore on the east side of Plymouth Dock, opposite to Stonehouse, I found a specimen of schistose micaceous limestone, containing a shell of the bivalve kind: it was struck off from the solid rock, and cannot possibly be considered as an adventitious fossil.

Now, no rocks can be more decided primary than those about Plymouth. They consist of calcareous strata, in the form either of marble or micaceous limestone, alternating with varieties of the same schistus, which prevails through Cornwall to the west, and extends eastward into Dartmoor, and on the sea-coast, as far as the Berry-head. These all intersect the horizontal plane, in a line from east to west nearly; they are very erect, those at Plymouth being elevated to the north.

Though, therefore, the remains of marine animals are not frequent among the primary rocks, they are not excluded from them; and hence the existence of shell-fish and zoophytes, is clearly proved to be anterior to the formation even of those parts of the present land which are justly accounted the most ancient.

153. The rocks which contain sand or gravel, which are of a granulated texture, must also be considered as carrying in themselves a testimony of the most unequivocal kind, of their being derived from the _detritus_ and waste of former rocks. Now, the fact stated in the text, concerning sand found in schistus, most justly accounted primary, might be exemplified by actual reference to many spots on the earth's surface. A few such will be sufficient in this place.

St Gothard is a central point, in one of the greatest tracts of primary mountains on the face of the earth, yet arenaceous strata are found in its vicinity. Between Ayrolo and the Hospice of St Gothard, Saussure found a rock, composed of an arenaceous or granular paste, including in it hornblende and garnets. He is somewhat unwilling to give the name _gres_ to this stone, which M. Besson had done; but he nevertheless describes it as having a granulated structure.[67]

[Footnote 67: Voyages aux Alpes, tom. iv. § 1822.]

Among the most indurated rocks that compose the mountains of this island, many are arenaceous. Thus, on the western coast of Scotland, the great body of high and rugged mountains on the shores of Arafaig, &c. from Ardnamurchan to Glenelg, consists, in a great measure, of a granitic sandstone, in vertical beds. This stone sometimes occupies great tracts; at other times it is alternated with the micaceous, or other varieties of primary schistus; it occurs, likewise, in several of the islands, and is a fossil which we hardly find described or named by the writers on mineralogy. Much, also, of a highly indurated, but granulated quartz, is found in several places in Scotland, in beds or strata, alternated with the common schistus of the mountains. Remarkable instances of this may be seen on the north side of the ferry of Balachulish, and again on the sea-shore at Cullen. At the latter, the strata are remarkably regular, alternating with different species of schistus. At the former, the quartz is so pure, that the stone has been mistaken for marble.

These examples are perhaps sufficient; but I must add, that in the micaceous and talcose schisti themselves, thin layers of sand are often found, interposed between the layers of mica or talc. I have a specimen, from the summit of one of the highest of the Grampian mountains, where the thin plates, of a talcky or asbestine substance, are separated by layers of a very fine quartzy sand, not much consolidated.

The mountain from which it was brought, consists of vertical strata, much intersected by quartz veins. It is impossible to doubt, in this instance, that the thin plates of the one substance, and the small grains of the other, were deposited together at the bottom of the sea, and that they were alike produced from the degradation of rocks, more ancient than any which now exist.

154. In the Neptunian system, as improved by WERNER, an attempt is made to take off the force of such instances as are produced in § 8, 9, and 152, &c. by distinguishing rocks, as to their formation, into three different orders, the primitive, the intermediate, and the secondary, or, to speak more properly, into primary, secondary, and tertiary. The same mineralogist distinguishes, among the materials of these rocks, between what he terms chemical and mechanical deposits. By mechanical deposits, are understood sand, gravel, and whatever bears the mark of fracture and attrition; by chemical deposits, those which are regularly crystallized, or which have a tendency to crystallization, and in which the action of mechanical causes cannot be traced. This distinction is founded in nature, and proceeds on real and palpable differences; but the application made of it to the three kinds of strata just enumerated, seems by no means entitled to the same praise.

The primitive rocks contain, it is said, none but chemical deposits, and are entirely composed of them: the intermediate contain a mixture of both, and also some vestiges of organized bodies: the secondary consist almost entirely of the mechanical, or of the remains of such bodies, with little of the chemical. The first of these, then, are held to contain no mark or vestige whatsoever of any thing more ancient than themselves, and are, in the strictest sense, primeval, or formed of the first materials, deposited by the immense ocean which originally encompassed the globe.

After them were formed the intermediate, mostly consisting of chemical deposits, but containing also some animal remains, and some spoils from the land, subjected to the various kinds of destruction, which even then made a part of the order of nature. These rocks, it is alleged, are chiefly argillaceous, are less indurated than the primary, and not intersected by veins of quartz.

The secondary were formed from the remains of the other two, and contain more mechanical deposits than any other.

This sketch of what I understand to be Werner's opinion concerning the different formation of the strata, is chiefly taken from a view of his system, in the _Journal de Physique_ for 1800.

155. The main objection to the distinction here made between the primary and the intermediate strata, is founded on the facts that have been just stated. The sandstone of St Gothard is from a country having every character of a primary one in the highest perfection. The instances I have mentioned from the Highlands of Scotland, are from mountains, less elevated indeed than the Alps, but where the rock is micaceous, talcose, or siliceous, in planes erect to the horizon, and intersected by veins' of quartz. The shells from Plymouth are from a rock, that Werner would, I think, admit to be truly primitive. Those from the lakes, also, are from the centre of a country, occupied by porphyry, schorl, hornstone-schistus, and many others, about the order of which there can be no dispute. It is true, that in this tract there are argillaceous strata, of the kind that might be accounted intermediate, were they not interposed among those that are certainly primary; and this very intermixture shows, how little foundation there is for the distinction attempted to be made between the formation of the one and of the other. If there is any principle in mineralogy, which may be considered as perfectly ascertained, it is, that rocks similarly stratified, and alternated with one another, are of the same formation.

Hence we conclude, that there is _no order of strata yet known_, that does not contain proofs of the existence of more ancient strata. We see nothing, in the strict sense, primitive. It must be understood, that what is here said has no reference to granite, which I do not consider as a stratified rock, and in which neither the remains of organized bodies, nor sand, have I believe been ever found; though some instances will be hereafter mentioned, where granite contains fragments of other stone, viz. of different kinds of primary schistus.

To the instances of sand involved in primary schistus, I might have added many from the rocks of that order on the coast of Berwickshire, of which mention is so often made in these Illustrations; but I wished to draw the evidence from those rocks that are most unequivocally primary, and to which the Wernerian distinction of _intermediate_ could not possibly be applied.

If any one assert, as M. De Luc has done, that sand is a chemical deposit, a certain mode of crystallization which quartz sometimes assumes, let him draw the line which separates sand from gravel; and let him explain why quartz, in the form of sand, is not found in mineral veins, in granite, nor in basaltes, that is, in none of the situations where the appearances of crystallization are most general and best ascertained.

NOTE V. § 10.

_Transportation of the
materials of the strata._

156. The great transportation or _travelling_ of the materials of the strata, supposed by Dr Hutton, has been treated as absurd by some of his opponents, particularly De Luc and Kirwan. These philosophers seem not to have observed, that their own system, and indeed every system which derives the secondary strata from the primary, involves a transportation of materials, hardly less than is supposed in the Huttonian theory, and a degradation of the primeval mountains, in many instances much greater. To form some notion of this degradation, it must be recollected, that the primeval mountains, which furnished the materials of the secondary strata in the plains, cannot have stood in the place now occupied by these plains. This is obvious; and therefore we must necessarily regard the secondary strata as derived from the primitive mountains which are the nearest to them, and of which a part still remains. This part is sufficient to define the base of the original mountains; and the quantity of the secondary strata which surround them may help us to make some estimate of their height. Let us take, for instance, the extensive tract of secondary country about Newcastle, where coal mines have been sunk through a succession of secondary strata, to the depth of more than a thousand feet. This secondary country may be considered as comprehending almost the whole of the counties of Northumberland and Durham, and probably as extending very far under the part of the German Ocean which washes their coasts; and the whole strata composing it must be derived, on the hypothesis we are now considering, from the Cheviot Hills, on one side, and from those in the high parts of Westmoreland and Cumberland on the other, comprehending the Alston-Moor Hills, and the large group of primary mountains, so well known from the sublime and romantic scenery of the _Lakes_. Now, the mountains which stood on this base, had not only to supply the materials for the tract already mentioned, on the east, but had also their contingent to furnish to the plains on the west and north; the Cheviots to Roxburghshire and Berwickshire; the Northumberland mountains to the coal strata about Whitehaven, and along the sea coast to Lancashire. On the whole, we shall not exceed the truth, if we suppose, that the secondary strata, at the feet of the above mountains, are six or seven times more extensive than the base of the mountainous tract. If then we take the medium depth of these secondary strata to be one thousand feet, it is evident, that the mass of stone which composes them, if it were placed on the same base with the primitive mountains, would reach to the height of six thousand feet. This is supposing the mass to preserve the breadth of its base uniformly to the summit; but if it be supposed to taper, as mountains usually do, we must multiply this six thousand by three, in order to have the height of these primeval mountains, which, therefore, were originally elevated not less than eighteen thousand feet; in height, therefore, they once rivalled the Cordilleras, and are now but poorly represented by the hills of Skidaw and Helvellyn. It were easy to show, that this estimate is still below the result that strictly follows from the Neptunian hypothesis; but it is unnecessary to proceed further, than to prove, that the principle of the degradation of mountains, is involved in that hypothesis to an excessive and improbable degree; and that the supporters of it, have either been guilty of the inconsistency of refusing to Dr Hutton the moderate use of a principle, which they themselves employ in its utmost extent, or of not having sufficiently adverted to the consequences of their own system.

157. The formation of secondary strata from the degradation of the contiguous mountains, on close examination, is subject to many other difficulties of the same kind. Mountains of secondary strata, and nearly horizontal, are found in this island of the height of three thousand feet. Such are Ingleborough, Wharnside, and perhaps some others on the west of Yorkshire. The whole chain, indeed, for secondary mountains, is of great elevation. The strata are of limestone, and of a very coarse-grained sandstone, alternating with it. No mountains can more clearly point out, that the strata of which they consist were once continued quite across the vallies which now separate them; and hence, if the materials of those strata were indeed furnished from any contiguous primitive mountains, the latter must have been, out of all proportion, higher than any mountains now in Britain.

158. Thus, a great degradation of the primitive mountains, and of course a great travelling of their materials, is proved to make a necessary part of the Neptunian theory. The extent of this travelling or transportation may be rendered more evident, if we apply a similar mode of reasoning to larger portions of the globe. The north-west of Europe furnishes us an instance of a very extensive tract of secondary country, comprehending the greater part of Britain, the whole of Flanders and Holland, part of Germany, the northern provinces of France, and probably the bed of the German Ocean, at least for a great extent. Within this circle almost all is secondary, and on the sides of it all round are placed ridges or groups of primitive mountains, namely the mountains of Auvergne, at least in part, and going round by the east, the Alps, the Vosges, the Hartz, the Highlands and Western Islands of Scotland, the hilly countries of Cumberland, Wales, and Cornwall. This zone of primitive mountains, on the supposition of the Neptunists, must have risen up in the form of islands in the great ocean, that originally covered the earth, forming a kind of circular Archipelago, including in its bosom a sea, which was from seven to five hundred miles in diameter. Over the whole of this extent, the _detritus_ of the above mountains must have been carried, in order to form the flat interjacent countries which are now exposed to our view. Such then, even on their own supposition, is the extent to which the Neptunists must admit that the materials of the primeval mountains were transported by the ocean.

159. This transportation of materials, may not be so great as that which is involved in Dr Hutton's theory, but is such as should make the enemies of his system consider, how nearly the principles they _must_ introduce, agree with those that they _would_ reject. This is one fact, out of many, which shows, that there is at present a much nearer agreement between the systems of geology, than between their authors.

160. To these facts, demonstrating the great transportation of fossils in some former conditions of the globe, we may add another, recognised by all mineralogists. The animal exuviæ contained in limestone and marble, are often known to belong to seas, extremely remote from the countries where they are now found. In the chalk-beds of England, in the limestones of France, a great proportion of the petrifactions belong to the tropical seas, and appear to have been brought from the vicinity of the equator. Buffon observes, that of the fossil shells found in France, it has been disputed, whether the foreign are not more numerous than the native; and, though he is himself of opinion that they are not, it is evident that they must bear a considerable proportion to the whole.[68] In the petrifactions of Monte Bolca, near Verona, where the impressions of fish are preserved between the laminæ of a calcareous schistus, one hundred and five different species have been enumerated, of which thirty-nine are from the Asiatic seas, three from the African, eighteen from those of South, and eleven from those of North America.[69] Similar observations have been made on the marine plants, and the impressions of vegetables, found in rocks, in different parts of Europe. At St Chaumont, near Lyons, is found an argillaceous schistus, covering a bed of coal, every lamina of which is marked with the impressions of the stem, leaf, or other part of some plant; and it happens, says M. FONTENELLE, by an unaccountable destination of nature, that not one of these plants is a native of France. They are all ferns of different species, peculiar to the East Indies, or the warmer climates of America. Here also was found the fruit of a tree, which grows only on the coasts of Malabar and Coromandel.[70]

[Footnote 68: Buffon, Théorie de la Terre, art. 8.]

[Footnote 69: Saussure, Voyages aux Alpes, tom. iii. § 1535.]

[Footnote 70: Mém. De l'Acad. Des Sciences, 1718, p. 3 and 287; and 1721, p. 89, &c.]

The same holds of the bodies of amphibious animals which now make a part of the fossil kingdom. The head and the bones of crocodiles have been found in the island of Shepey, at the mouth of the Thames; and the remains of an animal of the same species, but of a variety now peculiar to the Ganges, have been discovered in the alum rocks on the coast of Yorkshire.[71] These proofs of the transportation of materials by the sea, have the advantage of involving nothing hypothetical, and of being equally addressed to the geologists of every persuasion.

[Footnote 71: Phil. Trans. vol. l. p. 688. CAMPER denies that the remains here mentioned belong to the crocodile, or any amphibious animal, and refers them to the balænaæ. He passes the same judgment on those fossil bones from St Peter's Mount, near Maestricht, which have been supposed to belong to the crocodile; he looks on them as belonging to whales, though of an unknown species. In this Mount, so famous for its petrifactions, he finds many specimens of bones, which he thinks belong to the turtle. Phil. Trans. vol lxxvi. p. 443. The opinion of an author, so well skilled in comparative anatomy, must be regarded as of great weight: if it takes from our argument in one part, it adds to it in another, and the acquisition of the turtle makes up abundantly for the loss of the crocodile.]

On this subject I cannot help observing, that the accurate comparison of the animal exuviæ of the mineral kingdom, with their living archetypes, is not merely a curious inquiry, but is one that may lead to important consequences, concerning the nature and direction of the forces which have changed, and are continually changing, the surface of the earth.

161. These remarks I have thought it proper to add to the proofs of the composition of the present from former strata, in order to show, that the great transportation of materials involved in that supposition, is not only conformable to the hypothesis of the Neptunists concerning the secondary strata, but is also proved by the most direct evidence, independently of all hypothesis. All this reasoning regards the ancient state of the globe. Whether such a travelling of stony bodies makes a part of the system now actually carrying on, will be considered in another place.[72]

[Footnote 72: See NOTE XIX.]

NOTE VI. § 13.

_Mr Kirwan's notion of precipitation._