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Theory of the Earth, by James Hutton, [1788 and 1795], at


An Examination of Mr KIRWAN'S Objections to the Igneous Origin of Stony Substances.

A theory which is founded on a new principle, a theory which has to make its way in the public mind by overturning the opinions commonly received by philosophising men, and one which has nothing to recommend it but the truth of its principles, and the view of wisdom or design to which it leads, neither of which may perhaps be perceived by the generality of people, such a theory, I say, must meet with the strongest opposition from the prejudices of the learned, and from the superstition of those who judge not for themselves in forming their notions, but look up to men of science for authority. Such is the case with some part of the Theory of the Earth, which I have given, and which will probably give offence to naturalists who have espoused an opposite opinion. In order, then, to obtain the approbation of the public, it may not be enough to give a theory that should be true, or altogether unexceptionable it may be necessary to defend every point that shall be thought exceptionable by other theorists, and to show the fallacy of every learned objection that may be made against it. It is thus, in general, that truth and error are forced to struggle together, in the progress of science; and it is only in proportion as science removes erroneous conceptions, which are necessarily in the constitution of human knowledge, that truth will find itself established in natural philosophy.

Mr Kirwan has written a dissertation, entitled, Examination of the Supposed Igneous Origin of Stony Substances, which was read in the Royal Irish Academy. The object of that dissertation is to state certain objections, which have occurred to him, against the Theory of the Earth published in the Transactions of the Edinburgh Royal Society; and he has attacked that theory in all the points where it appears to him to be vulnerable. It is to these objections that I am now to give an answer. The authority given to this dissertation, by the Royal Irish Academy, as well as the reputation of the author, make it necessary for me to endeavour to put in their true light the facts alleged in that performance, and to analyse the arguments employed, in order to judge of the reasoning by which the theory of mineral fusion is refuted in this Examination.

A theory founded on truth, and formed according to the proper rules of science, can ever suffer from a strict examination, by which it would be but the more and more confirmed. But, where causes are to be traced through a chain of various complicated effects, an examination not properly conducted upon accurate analytical principles, instead of giving light upon a subject in which there had been obscurity and doubt, may only serve to perplex the understanding, and bring confusion into a subject which was before sufficiently distinct. To redress that evil, then, must require more labour and some address; and this is an inconveniency that may be looked for, more or less, in every controversial discussion.

I do not mean to enter any farther into the defence of my theory in this chapter, than what is necessary to answer a man of science and respectability, who has stated his objections. The observations which he has made appear to me to be founded on nothing more than common prejudice, and misconceived notions of the subject. I am therefore to point out that erroneous train of reasoning, into which a hasty superficial view of things, perhaps, has led the patron of an opposite opinion to see my theory in an unfavourable light. This, however, is not all; for, that train of inconsequential reasoning is so congenial with the crude and inconsiderate notion generally entertained, of solid mineral bodies having been formed by the infiltration of water into the earth, that no opportunity should be lost of exposing an erroneous manner of reasoning, which is employed in supporting a hypothesis founded upon certain operations of the surface of this earth that cannot be properly applied to the formation of mineral bodies. This object, therefore, so far as it may come in the way, will be attended to in this discussion, although I shall have another opportunity of farther enlarging upon that subject.

Our author begins by examining a geological operation, the very opposite to that of mineral consolidation, and which would seem to have little connection with the subject of this dissertation. In my theory, I advanced two propositions with regard to the economy of this world: First, That the solid masses of this earth, when exposed to the atmosphere, decay, and are resolved into loose materials, of which the vegetable soil upon the surface is in part composed; and, secondly, That these loose materials are washed away by the currents of water, and thus carried at last into the sea. Our author says "Here are two suppositions, neither of which is grounded on facts;" and yet he has but the moment before made the following confession: "That the soil, however, receives an increase from some species of stones that moulder by exposition to the air cannot be denied, but there is no proof that all soil has arisen from decomposition."—Surely all soil, that is made from the hard and compact body of the land, which is my proposition, must have arisen from decomposition; and I have no where said, that all the soil of this earth is made from the decomposition or detritus of those stony substances; for, masses of looser sand and softer substances contribute still more to the formation of vegetable soils.

With regard to the other proposition, our author says, "Soil is not constantly carried away by the water, even from mountains."—I have not said that it is constantly washed away; for, while it is soil in which plants grow, it is not travelling to the sea, although it be on the road, and must there arrive in time. I have said, that it is necessarily washed away, that is, occasionally. M. de Luc's authority is then referred to, as refuting this operation of water and time upon the soil. Now, I cannot help here observing, that our author seems to have as much misapprehended M. de Luc's argument as he has done mine. That philosopher, in his letters to the Queen, has described most accurately the decay of the rocks and solid mountains of the Alps and Jura, and the travelling of their materials by water, although he does not carry them to the sea. It is true, indeed, that this author, who supposes the present earth on which we dwell very young, is anxious to make an earth, in time, that shall not decay nor be washed away at all; but that time is not come yet; therefore the authority, here given against my theory, is the speculative supposition, or mere opinion, of a natural philosopher, with regard to an event which may never come to pass, and which I shall have occasion to consider fully in another place.

Our author had just now said, that I have advanced two suppositions, neither of which is grounded on facts: Now, with regard to the one, he has acknowledged, that the mouldering of stones takes place, which is the fact on which that proposition is grounded; and with regard to the other, the only authority given against it is founded expressly upon the moving of soil by means of the rain water, in order to make sloping plains of mountains. Here, therefore, I have grounded my propositions upon facts; and our author has founded his objections, first, upon a difficulty which he has himself removed; and, secondly, upon nothing but a visionary opinion, with regard to an earth which is not yet made, and which, when once made, is never more to change.

After making some unimportant observations,—of all water not flowing into the sea,—and of the travelled materials being also deposited upon the plains, etc. our author thus proceeds: "Hence the conclusion of our author relative to the imperfect constitution of the globe falls to the ground; and the pains he takes to learn, by what means a decayed world may be renovated, are superfluous."—The object of my theory is to show, that this decaying nature of the solid earth is the very perfection of its constitution, as a living world; therefore, it was most proper that I should take pains to learn by what means the decayed parts might be renovated. It is true, indeed, that this will be superfluous, when once that constitution of the earth, which M. de Luc thinks is preparing, shall be finished; but, in the mean time, while rivers carry the materials of our land, and while the sea impairs the coast, I may be allowed to suppose that this is the actual constitution of the earth.

I cannot help here animadverting upon what seems to be our author's plan, in making these objections, which have nothing to do with his examination. He accuses me of giving this world a false or imperfect constitution, (in which the solid land is considered as resolvable, and the materials of that land as being washed away into the sea,) for no other reason, that I can see, but because this may imply the formation of a future earth, which he is not disposed to allow; and, he is now to deny the stratified construction of this present earth to have been made by the deposits of materials at the bottom of the sea, because that would prove the existence of a former earth, which is repugnant to his notion of the origin of things, and is contrary, as he says, to reason, and the tenor of the Mosaic history. Let me observe, in passing, that M. de Luc, of whose opinions our author expresses much approbation, thinks that he proves, from the express words and tenor of the Mosaic history, that the present earth was at the bottom of the sea not many years ago, and that the former earth had then disappeared.

But, what does our author propose to himself, in refusing to admit my view of the operations which are daily transacting upon the surface of this earth, where there is nothing dark or in the least mysterious, as there may be in the mineral regions? Does he mean to say, that it is not the purpose of this world to provide soil for plants to grow in? Does he suppose that this soil is not moveable with the running water of the surface? and, Does he think that it is not necessary to replace that soil which is removed? This is all that I required in that constitution of the world which he has thus attacked; and I wish that he or any person would point out, in what respect I had demanded any thing unreasonable, or any thing that is not actually to be observed every day.

Thus I have endeavoured to show, that our author has attacked my theory in a part where I believe it must be thought invulnerable; but this is only, I presume, in order that he may make an attack with more advantage upon another part, viz. the composition of strata from the materials of an earth thus worn out in the service of vegetation,—materials which are necessarily removed in order to make way for that change of things in which consists the active and living system of this world. If he succeed in this attempt to refute my theory of the original formation of strata, he would then doubtless find it more easy to persuade philosophers that the means which I employ in bringing those materials again to light, when transformed into such solid masses as the system of this earth requires, are extravagant, unnatural, and unnecessary. Let us then see how he sets about this undertaking.

With regard to the composition of the earth, it is quoted from my theory, that the solid parts of the globe are in general composed of sand, gravel, argillaceous and calcareous strata, or of various compositions of these with other substances; our author then adds, "This certainly cannot be affirmed as a fact, but rather the contrary; it holds only true of the surface, the basis of the greater part of Scotland is evidently a granitic rock, to say nothing of the continents, both of the Old and New World, according to the testimony of all mineralogists." This proposition, with regard to the general composition of the earth, I have certainly not assumed, I have maintained it as a fact, after the most scrupulous examination of all that, with the most diligent search, I have been able to see, and of all that authors have wrote intelligibly upon the subject. If, therefore, I have so misrepresented this great geological fact on which my theory is absolutely founded, I must have erred with open eyes; and my theory of the earth, like others which have gone before it, will, upon close examination, appear to be unfounded, as the dissertation now before us is endeavouring to represent it.

Our author here, I think, alleges that the contrary to this, my fundamental proposition, is the truth; and he has given us Scotland as an example in which his assertion (founded upon the testimony of all mineralogists), is illustrated. Now my geological proposition should certainly be applicable to Scotland, which is the country that I ought to be best acquainted with; consequently, if what our author here asserts be true, I would have deserved that blame which he is willing to throw on me. Let me then beg the readers attention for a moment, that I may justify myself from that charge, and place in its proper light this authority, upon so material a point in geology.

I had examined Scotland from the one end to the other before I saw one stone of granite in its native place, I have moreover examined almost all England and Wales, (excepting Devonshire and Cornwall) without seeing more of granite than one spot, not many hundred yards of extent; this is at Chap; and I know, from information, that there is another small spot in the middle of England where it is just seen. But, let me be more particular with regard to Scotland, the example given in proof.

I had travelled every road from the borders of Northumberland and Westmoreland to Edinburgh; from Edinburgh, I had travelled to Port-Patrick, and from that along the coast of Galloway and Airshire to Inverary in Argyleshire, and I had examined every spot between the Grampians and the Tweedale mountains from sea to sea, without seeing granite in its place. I had also travelled from Edinburgh by Grief, Rannock, Dalwhiny, Fort Augustus, Inverness, through east Ross and Caithness, to the Pentland-Frith or Orkney islands, without seeing one block of granite in its place. It is true, I met with it on my return by the east coast, when I just saw it, and no more, at Peterhead and Aberdeen; but that was all the granite I had ever seen when I wrote my Theory of the Earth. I have, since that time, seen it in different places; because I went on purpose to examine it, as I shall have occasion to describe in the course of this work.

I may now with some confidence affirm, from my own observation, and from good information with regard to those places where I have not been, except the northwest corner, I may affirm, I say, that instead of the basis of the greatest part of Scotland being a granitic rock, which our author has maintained as an evident thing, there is very little of it that is so; not perhaps one five hundred part. So far also as I am to judge from my knowledge of the mineral construction of England and Wales, which I have examined with the greatest care, and from the mineral chart which my friend Mr Watt made for me from his knowledge of Cornwall, I would say that there is scarcely one five hundred part of Britain that has granite for its basis. All the rest, except the porphyry and basaltes, consists of stratified bodies, which are composed more or less of the materials which I mentioned, generally, in the above quotation, and which our author would dispute.

But do not let me take the advantage of this error of our author with regard to the mineralogy of Scotland, and thus draw what may be thought an undue conclusion in favour of my general theory; let us go over and examine the continent of Europe, and see if it is any otherwise there than in Britain. From the granite of the Ural mountains, to that which we find in the Pyrenees, there is no reason, so far as I have been able to learn, to conclude that things are formed either upon any other principle, or upon a different scale. But, instead of one five hundred part, let us suppose there to be one fiftieth part of the earth in general resting upon granite, I could not have expressed myself otherwise than I have done; for, when I maintained that the earth in general consisted of stratified bodies, I said that this was only nine tenths, or perhaps ninety-nine hundredths of the whole, and I mentioned that there were other masses of a different origin, which should be considered separately. Our author, on the contrary, asserts that the Old and New Worlds, as well as Scotland, are placed upon granite as a basis, which he says is according to the testimony of all mineralogists. I shall have occasion to examine this opinion of mineralogists, in comparing it with those masses of granite which appear to us; and I hope fully to refute the geological, as well as mineralogical notions with regard to that body. In the mean time, let me make the following reflection, which here naturally occurs.

My Theory of the Earth is here examined,—not with the system of nature, or actual state of things, to which it certainly should have corresponded,—but with the systematic views of a person, who has formed his notions of geology from the vague opinion of others, and not from what he has seen. Had the question been, How far my theory agreed with other theories, our author might very properly have informed his readers that it was diametrically opposite to the opinions of mineralogists; but, this was no reason for concluding it to be erroneous; on the contrary, it is rather a presumption that I may have corrected the error of mineralogists who have gone before me, in like manner as it is most reasonable to presume that our author may have corrected mine. Let us then proceed to examine how far this shall appear to be the case.

Our author has stated very fairly from the Theory, viz. That all the strata of the earth, not only those consisting of calcareous masses, but others superincumbent on these, have had their origin at the bottom of the sea, by the collection of sand, gravel, shells, coralline, and crustaceous bodies, and of earths and clays variously mixed, separated, and accumulated. He then adds, "Various geological observations contradict this conclusion. There are many stratified mountains of argillaceous slate, gneiss, serpentine, jasper, and even marble, in which either sand, gravel, shells, coralline, or crustaceous bodies are never, or scarce ever found."

Here our author seems to have deceived himself, by taking a very partial view of things which should be fully examined, and well understood, before general conclusions are to be drawn from those appearances; for, although those particular objects may not be visible in the strata which he has enumerated, or many others, they are found in those strata which are either immediately connected and alternated with them, or with similar strata; something to that purpose I think I have said; and, if I had not, it certainly requires no deep penetration to have seen this clear solution of that appearance of those objects not being found in every particular stratum. He says that those marks of known materials are never or scarce ever found;—by scarce ever he surely means that they are sometimes found; but if they shall only once be found, his argument is lost. I have not drawn my geological conclusion from every particle in strata being distinguishable, but from there being certain distinguishable particles in strata, and from our knowing what had been the former state and circumstances of those distinguished parts.

If every stone or part of a stratum, in which those known objects are not immediately visible, must be considered as so many geological observations that contradict my theory, (of strata being formed from the materials of a former earth), then, surely every stone and every stratum which visibly contains any of those materials, must prove my theory. But if every stratum, where these are found in any part of it, is to be concluded as having had its origin at the bottom of the sea; and, if every concomitant stratum, though not having those objects visible or sufficiently distinct, must be considered as having had the same or a similar origin, that pretended contradiction of my theory comes to no more than this, that every individual stone does not bear in it the same or equal evidence of that general proposition which necessarily results from the attentive consideration of the whole, including every part.

But to see how necessary it is to judge in this manner, not partially, but upon the whole, we may observe, that there are two ways by which the visible materials or distinguishable bodies of a former earth, not only may be rendered invisible in the composition of our present earth, but must be so upon many occasions. These are, first, by mechanical comminution, which necessarily happens, more or less, in that operation by which bodies are moved against one another, and thus transported from the land to the bottom of the deepest seas; secondly, by chemical operations, (whatever these may be, whether the action of water or of fire, or both), which are also necessarily employed for consolidating those loose materials, that are to form the rocks and stones of this earth, and by means of which those materials are to have their distinguishable shapes affected in all degrees and obliterated. Therefore, to demand the visible appearance of those materials in every stratum of the earth, or in every part of a stratum, is no other than to misunderstand the subject altogether. The geological observations, which have been thus alleged as contradicting my theory, are stratified bodies, containing proofs of the general origin which I attribute to the earth, but proofs which may not always be seen with equal facility as those which even convince the vulgar.

Our author has surely perplexed himself with what writers of late have said concerning primitive mountains as they are called, a subject of deeper search, than is commonly imagined, as I hope to show in the course of this work. It is an interesting subject of investigation, as giving us the actual view of those operations of nature which, in forming my Theory of the Earth, more general principles had led me to conclude might be. But, it is a subject which, I am afraid, will lead me to give farther offence to our author, however innocent I may be in giving nothing but what I have from nature.

The reason for saying so is this; I am blamed for having endeavoured to trace back the operations of this world to a remote period, by the examination of that which actually appears, contrary, as is alleged, "to reason, and the tenor of the Mosaic history, thus leading to an abyss, from which human reason recoils, etc." In a word, (says our author), "to make use of his own expression, We find no vestige of a beginning. Then this system of successive worlds must have been eternal." Such is the logic by which, I suppose, I am to be accused of atheism. Our author might have added, that I have also said—we see no prospect of an end; but what has all this to do with the idea of eternity? Are we, with our ideas of time, (or mere succession), to measure that of eternity, which never succeeded any thing, and which will never be succeeded? Are we thus to measure eternity, that boundless thought, with those physical notions of ours which necessarily limit both space and time? and, because we see not the beginning of created things, Are we to conclude that those things which we see have always been, or been without a cause? Our author would thus, inadvertently indeed, lead himself into that gulf of irreligion and absurdity into which, he alleges, I have boldly plunged.

In examining this present earth, we find that it must have had its origin at the bottom of the sea, although our author seems willing to deny that proposition. Farther, in examining the internal construction of this stratified and sea-born mass, we find that it had been composed of the moved materials of a former earth; and, from the most accurate and extensive examination of those materials, which in many places are indeed much disguised, we are led necessarily to conclude, that there had been a world existing, and containing an animal, a vegetable, and a mineral system. But, in thus tracing back the natural operations which have succeeded each other, and mark to us the course of time past, we come to a period in which we cannot see any farther. This, however, is not the beginning of those operations which proceed in time and according to the wise economy of this world; nor is it the establishing of that, which, in the course of time, had no beginning; it is only the limit of our retrospective view of those operations which have come to pass in time, and have been conducted by supreme intelligence.

My principal anxiety was to show how the constitution of this world had been wisely contrived; and this I endeavoured to do, not from supposition or conjecture, but from its answering so effectually the end of its intention, viz. the preserving of animal life, which we cannot doubt of being its purpose. Here then is a world that is not eternal, but which has been the effect of wisdom or design.

With regard again to the prospective view of the creation, How are we to see the end of that wise system of things which so properly fulfils the benevolent intention of its maker,—in giving sustenance to the animal part, and information to intellectual beings, who, in these works of nature, read what much concerns their peace of mind,—their intellectual happiness? What then does our author mean, in condemning that comprehensive view which I have endeavoured to take of nature? Would he deny that there is to be perceived wisdom in the system of this world, or that a philosopher, who looks into the operations of nature, may not plainly read the power and wisdom of the Creator, without recoiling, as he says, from the abyss? The abyss, from which a man of science should recoil, is that of ignorance and error.

I have thus shown, that, from not perceiving the wise disposition of things upon the surface of this earth for the preservation of vegetable bodies, our author has been led to deny the necessary waste of the present earth, and the consequent preparation of materials for the construction of another; I have also shown, that he denies the origin which I had attributed to the stratified parts of this earth, as having been the collection of moving materials from a former earth; and now I am come to consider the professed purpose of this paper, viz. the examination of solid stony substances which we find in those strata of our earth, as well as in more irregular masses. Here, no doubt, my theory would have been attacked with greater success, had our author succeeded in pointing out its error with regard to the original composition of those indurated bodies, to which I ascribe fusion as the cause of their solidity. For, if we should, according to our author's proposition, consider those consolidated bodies as having been originally formed in that solid state, here the door might be shut against any farther investigation;—But to what purpose?—Surely not to refute my theory, but to explode every physical inquiry farther on the subject, and thus to lead us back into the science of darkness and of scepticism. But let us proceed to see our author's sentiments on this subject.

As I had proved from matter of fact, or the actual appearances of nature, that all the strata of the earth had been formed at the bottom of the sea, by the subsidence of those materials which either come from the decaying land, or are formed in the sea itself, it was necessary that I should consider in what manner those spongy or porous bodies of loose materials, gathered together at the bottom of the sea, could have acquired that consolidated state in which we find them, now that they are brought up to our examination. Upon this occasion, our author says, "The particles which now form the solid parts of the globe need not be supposed to have originally been either spongy or porous, the interior parts at the depth of a few miles might have been originally, as at present, a solid mass." If, indeed, we shall make that supposition, we may then save ourselves the trouble of considering either how the strata of the earth have been formed or consolidated; for, they might have been so originally. But, how can a naturalist who had ever seen a piece of Derbyshire marble, or any other shell limestone, make that supposition? Here are, to the satisfaction of every body of common understanding who looks at them, bodies which are perfectly consolidated, bodies which have evidently been formed at the bottom of the sea, and therefore which were not originally a solid mass. Mr Bertrand, it is true, wrote a book to prove that those appearances were nothing but a lusus naturae; and, I suppose he meant, with our author, that those strata had been also originally, as at present, a solid mass.

With regard to the consolidation of strata, that cardinal point for discussion, our author gives the following answer: "Abstracting from his own gratuitous hypothesis, it is very easy to satisfy our author on this head; the concreting and consolidating power in most cases arises from the mutual attraction of the component particles of stones to each other." This is an answer with regard to the concreting power, a subject about which we certainly are not here inquiring. Our author, indeed, has mentioned a consolidating power; but that is an improper expression; we are here inquiring, How the interstices, between the collected materials of strata, deposited at the bottom of the sea, have been filled with a hard substance, instead of the fluid water which had originally occupied those spaces. Our author then continues; "If these particles leave any interstices, these are filled with water, which no ways obstructs their solidity when the points of contact are numerous; hence the decrepitation of many species of stones when heated."

If I understand our author's argument, the particles of stone are, by their mutual attractions, to leave those hard and solid bodies which compose the strata, that is to say, those hard bodies are to dissolve themselves; but, To what purpose? This must be to fill up the interstices, which we must suppose occupied by the water. In that case, we should find the original interstices filled with the substances which had composed the strata, and we should find the water translated into the places of those bodies; here would be properly a transmutation, but no consolidation of the strata, such as we are here to look for, and such as we actually find among those strata. It may be very easy for our author to form those explanations of natural phenomena; it costs no tedious observation of facts, which are to be gathered with labour, patience, and attention; he has but to look into his own fancy, as philosophers did in former times, when they saw the abhorrence of a vacuum and explained the pump. It is thus that we are here told the consolidation of strata arises from the mutual attraction of the component particles of stones to each other; the power, by which the particles of solid stony bodies retain their places in relation to each other, and resist separation from the mass, may, no doubt, be properly enough termed their mutual attractions; but we are not here inquiring after that power; we are to investigate the power by which the particles of hard and stony bodies had been separated, contrary to their mutual attractions, in order to form new concretions, by being again brought within the spheres of action in which their mutual attractions might take place, and make them one solid body. Now, to say that this is by their mutual attraction, is either to misunderstand the proper question, or to give a most preposterous answer.

It is not every one who is fit to reason with regard to abstract general propositions; I will now, therefore, state a particular case, in illustration of that proposition which has been here so improperly answered. The strata of Derbyshire marbles were originally immense collections at the bottom of the sea, of calcareous bodies consisting almost wholly of various fragments of the entrochi; and they were then covered with an indefinite number of other strata under which these entrochi must have been buried. In this original state of those strata, I suppose the interstices between the fragments of the coralline bodies to have been left full of sea-water; at present we find those interstices completely filled with a most perfectly solid body of marble; and the question is, whether that consolidating operation has been the work of water and solution, by our naturalist's termed infiltration; or if it has been performed, as I have maintained, by the softening power or heat, or introduction of matter in the fluid state of fusion. Our author does not propose any other method for the consolidation of those loose and incoherent bodies, but he speaks of the mutual attraction of the component particles of stone to each other; Will that fill the interstices between the coralline bodies with solid marble, as well as consolidate the coralline bodies themselves? or, if it should, How are those interstices to be thus filled with a substance perfectly different from the deposited bodies, which is also frequently the case? But, how reason with a person who, with this consolidation of strata, confounds the well known operation by which the mortar, made with caustic lime and sand, becomes a hard body! One would imagine that he were writing to people of the last age, and not to chemical philosophers who know so well how that mortar is concreted.

To my argument, That these porous strata are found consolidated with every different species of mineral substance, our author makes the following observation: "Here the difficulties to the supposition of an aqueous solution are placed in the strongest light; yet it must be owned that they partly arise from the author's own gratuitous supposition, that strata existed at the bottom of the sea previous to their consolidation;"—gratuitous supposition!—so far from being a supposition of any kind, it is a self evident proposition; the terms necessarily imply the conclusion. I beg the readers attention for a moment to this part of our author's animadversion, before proceeding to consider the whole; for, this is a point so essential in my theory, that if it be a gratuitous supposition, as is here asserted, it would certainly be in vain to attempt to build upon it the system of a world.

That strata may exist, whether at the bottom of the sea, or any other where, without being consolidated, will hardly be disputed; for, they are actually found consolidated in every different degree. But, when strata are found consolidated, at what time is it that we are to suppose this event to have taken place, or this accident to have happened to them? —Strata are formed at the bottom of water, by the subsidence or successive deposits of certain materials; it could not therefore be during their formation that such strata had been consolidated; consequently, we must necessarily conclude, without any degree of supposition, that strata had existed at the bottom of the sea previous to their consolidation, unless our author can show how they may have been consolidated previous to their existing.

This then is what our author has termed a gratuitous supposition of mine, and which, he adds, "is a circumstance which will not be allowed by the patrons of the aqueous origin of stony substances, as we have already seen."—I am perfectly at a loss to guess at what is here alluded to by having been already seen, unless it be that which I have already quoted, concerning things which have been never seen, that is, those interior parts of the earth which were originally a solid mass.—I have hardly patience to answer such reasoning;—a reasoning which is not founded upon any principle, which holds up nothing but chimera to our view, and which ends in nothing that is intelligible;—but, others, perhaps, may see this dissertation of our author's in a different light; therefore, it is my duty to analyse the argument, however insignificant it may seem to me.

I have minutely examined all the stratified bodies which I have been able, during a lifetime, to procure, both in this country of Britain, and from all the quarters of the globe; and the result of my inquiry has been to conclude, that there is nothing among them in an original state, as the reader will see in the preceding chapter. With regard again to the masses which are not stratified, I have also given proof that they are not in their original state, such as granite, porphyry, serpentine, and basaltes; and I shall give farther satisfaction, I hope, upon that head, in the course of this work. I have therefore concluded, That there is nothing to be found in an original state, so far as we see, in the construction of this earth. But, our author answers, That the interior parts might have been in an original state of solidity.—So might they have been upon the surface of the earth, or on the summits of our mountains; but, we are not inquiring What they might have been, but What they truly are. It is from this actual state in which the solid parts of the earth are found, that I have endeavoured to trace back the different states in which they must have been; and, by generalising facts, I have formed a theory of the earth. If this be a wrong principle or manner of proceeding in a physical investigation, or if, proceeding upon that principle, I have made the induction by reasoning improperly on any occasion, let this be corrected by philosophers, who may reason more accurately upon the subject. But to oppose a physical investigation with this proposition, that things might have been otherwise, is to proceed upon a very different principle,—a principle which, instead of tending to bring light out of darkness, is only calculated to extinguish that light which we may have acquired.

I shall afterwards have occasion to examine how far the philosophers, who attribute to aqueous solution the origin of stony substances, have proceeded in the same inductive manner of reasoning from effect to cause, as they ought to do in physical subjects, and not by feigning causes, or following a false analogy; in the mean time, I am to answer the objections which have been made to the theory of the earth.

In opposition to the theory of consolidating bodies by fusion, our author has taken great pains to show, that I cannot provide materials for such a fire as would be necessary, nor find the means to make it burn had I those materials. Had our author read attentively my theory he would have observed, that I give myself little or no trouble about that fire, or take no charge with regard to the procuring of that power, as I have not founded my theory on the supposition of subterraneous fire, however that fire properly follows as a conclusion from those appearances on which the theory is founded. My theory is founded upon the general appearances of mineral bodies, and upon this, that mineral bodies must necessarily have been in a state of fusion. I do not pretend to prove, demonstratively, that they had been even hot, however that conclusion also naturally follows from their having been in fusion. It is sufficient for me to demonstrate, That those bodies must have been, more or less, in a state of softness and fluidity, without any species of solution. I do not say that this fluidity had been without heat; but, if that had been the case, it would have answered equally well the purpose of my theory, so far as this went to explain the consolidation of strata or mineral bodies, which, I still repeat, must have been by simple fluidity, and not by any species of solution, or any other solvent than that universal one which permeates all bodies, and which makes them fluid.

Our author has justly remarked the difficulty of fire burning below the earth and sea. It is not my purpose here to endeavour to remove those difficulties, which perhaps only exist in those suppositions which are made on this occasion; my purpose is to show, that he had no immediate concern with that question, in discussing the subject of the consolidation which we actually find in the strata of the earth, unless my theory, with regard to the igneous origin of stony substances, had proceeded upon the supposition of a subterraneous fire. It is surely one thing to employ fire and heat to melt mineral bodies, in supposing this to be the cause of their consolidation, and another thing to acknowledge fire or heat as having been exerted upon mineral bodies, when it is clearly proved, from actual appearances, that those bodies had been in a melted state, or that of simple fluidity. Here are distinctions which would be thrown away upon the vulgar; but, to a man of science, who analyses arguments, and reasons strictly from effect to cause, this is, I believe, the proper way of coming at the truth. If the patrons of the aqueous origin of stony substances can give us any manner of scientifical, i.e. intelligible investigation of that process, it shall be attended to with the most rigid impartiality, even by a patron of the igneous origin of those substances, as he wishes above all things to distinguish, in the mineral operations, those which, on the one hand, had been the effect of water, from those which, on the other hand, had been the immediate effect of fire or fusion;—this has been my greatest study. But, while mineralists or geologists give us only mere opinions, What is science profited by such inconsequential observations, as are founded upon nothing but our vulgar notions? Is the figure of the earth, e.g. to be doubted, because, according to the common notion of mankind, the existence of an antipod is certainly to be denied?

I am not avoiding to meet that question with regard to the providing of materials for such a mineral fire as may be required; no question I desire more to be asked to resolve; but it must not be in the manner that our author has put that question. He has included this supposed difficulty among a string of other arguments by which he would refute my theory with regard to the igneous origin of stony substances, as if I had made that fire a necessary condition or a principle in forming my theory of consolidation. Now, it is precisely the reverse; and this is what I beg that mineral philosophers will particularly attend to, and not give themselves so much unnecessary trouble, and me so disagreeable a talk. I have proved that those stony substances have been in the fluid state of fusion; and from this, I have inferred the former existence of an internal heat, a subterraneous fire, or a certain cause of fusion by whatever name it shall be called, and by whatever means it shall have been procured. The nature of that operation by which strata had been consolidated, like that by which they had been composed, must, according to my philosophy, be decided by ocular demonstration; from examining the internal evidence which is to be found in those bodies as we see them in the earth; because the consolidating operation is not performed in our sight, no more than their stratification which our author has also denied to have been made, as I have said, by the deposits of materials at the bottom of the sea. Now, with regard to the means of procuring subterraneous fire, if the consolidating operation shall be thus decided to have been that of fusion, as I think I have fully shown, and for which I have as many witnesses, perhaps as there are mineral bodies, then our author's question, (how I am to procure a fire) in the way that he has put it, as an argument against the fusion, would be at least useless; for, though I should here confess my ignorance with regard to the means of procuring fire, the evidence of the melting operation, or former fluidity of those mineral bodies, would not be thereby in the least diminished. If again no such evidence for the fusion of those bodies shall appear, and it be concluded that they had been consolidated by the action of water alone, as our author seems inclined to maintain, he would have no occasion to start difficulties about the procuring of fire, in order to refute a theory which then would fall of itself as having no foundation.

But in order to see this author's notion of the theory which he is here examining, it may be proper to give a specimen of his reasoning upon this subject of heat. He says, "That my supposition of heat necessary for consolidating strata is gratuitous, not only because it is unnecessary, as we have already shown, but also because it is inconsistent with our author's own theory." Let us now consider those two propositions. First, it is unnecessary, as we have already shown;— I have already taken particular notice of what we have been shown on this occasion, viz. That the earth at a certain depth may have been originally in a solid state; and, that, where it is to be consolidated, this is done by the mutual attraction of the stony particles. Here is all that we have been shown to make subterraneous heat, for the consolidation of strata, unnecessary; and now I humbly submit, if this is sufficient evidence, that mineral heat is a gratuitous supposition.

Secondly, "it is inconsistent with our author's own theory." Here I would beg the readers attention to the reasoning employed on this occasion. He says, "according to him these strata, which were consolidated by heat, were composed of materials gradually worn from a preceding continent, casually and successively deposited in the sea; Where then will he find, and how will he suppose, to have been formed those enormous masses of sulphur, coal, or bitumen, necessary to produce that immense heat necessary for the fusion of those vast mountains of stone now existing? All the coal, sulphur, and bitumen, now known, does not form the 100,000 part of the materials deposited within one quarter of a mile under the surface of the earth; if, therefore, they were, as his hypothesis demands, carried off and mixed with the other materials, and not formed in vast and separate collections, they could never occasion, by their combustion, a heat capable of producing the smallest effect, much less those gigantic effects which he requires."

Here is a comparative estimate formed between two things which have not any necessary relation; these are, the quantity of combustible materials found in the earth, on the one hand, and the quantity which is supposed necessary for hardening and consolidating strata, on the other. If this earth has been consolidated by the burning of combustible materials, there must have been a superfluity, so far as there is a certain quantity of these actually found unconsumed in the strata of the earth. Our author's conclusion is the very opposite; let us then see how he is to form his argument, by which he proves that the supposition of subterraneous heat for hardening bodies is gratuitous and unnecessary, as being inconsistent with my theory.

According to my theory, the strata of this earth are composed of the materials which came from a former earth; particularly these combustible strata that contain plants which must have grown upon the land. Let us then suppose the subterraneous fire supplied with its combustible materials from this source, the vegetable bodies growing upon the surface of the land. Here is a source provided for the supplying of mineral fire, a source which is inexhaustible or unlimited, unless we are to circumscribe it with regard to time, and the necessary ingredients; such as the matter of light, carbonic matter, and the hydrogenous principle. But it is not upon any deficiency of this kind that our author founds his estimate; it is upon the superfluity of combustible materials which is actually found in this earth, after it had been properly consolidated and raised above the surface of the sea. This is a method of reasoning calculated to convince only those who do not understand it; it is as if we should conclude that a person had died of want, because he had left provision behind him. Our author certainly means to employ nothing but the combustible minerals of the present earth, in feeding the subterraneous fire which is to concoct a future earth; in that case, I will allow that his provision is deficient; but this is not my theory.

I am not here to enter into any argument concerning subterraneous fire; the reader will find, in the foregoing theory, my reasons for concluding, That subterraneous fire had existed previous to, and ever since, the formation of this earth,—that it exists in all its vigour at this day,—that there is, in the constitution of this earth, a superfluity of subterranean heat,—and that there is wisely provided a proper remedy against any destructive effect to the system, that might arise from that superabundant provision of this necessary agent. Had our author attended to the ocular proof that we have of the actual existence of subterraneous fire, and to the physical demonstrations which I have given of the effects of heat in melting mineral bodies, he must have seen that those arguments of his, with regard to the difficulty or impossibility of procuring that fire, can only show the error of his reasoning. I am far from supposing that my theory may be free from inconsistency or error; I am only maintaining that, in all his confident assertions, this author has not hitherto pointed any of these out.

So far I have answered our author's objections as to consolidation, and I have given a specimen of his reasoning upon that subject; but with regard to my Theory of the Earth, although simple fluidity, without heat, would have answered the purpose of consolidating strata that had been formed at the bottom of the sea, it was necessary to provide a power for raising those consolidated strata from that low place to the summits of the continents; now, in supposing heat to be the cause of that fluidity which had been employed in the consolidation of those submarine masses, we find a power capable of erecting continents, and the only power, so far as I see, which natural philosophy can employ for that purpose. Thus I was led, from the consolidation of strata, to understand the nature of the elevating power, and, from the nature of that power, again to understand the cause of fluidity by which the rocks and stones of this earth had been consolidated.

Having thus, without employing the evidence of any fire or burning, been necessarily led to conclude an extreme degree of heat exerted in the mineral regions, I next inquire how far there are any appearances from whence we might conclude whether that active subterraneous power still subsists, and what may be the nature of that power. When first I conceived my theory, naturalists were far from suspecting that basaltic rocks were of volcanic origin; I could not then have employed an argument from these rocks as I may do now, for proving that the fires, which we see almost daily issuing with such force from volcanos, are a continuation of that active cause which has so evidently been exerted in all times, and in all places, so far as have been examined of this earth.

With regard to the degree of heat in that subterraneous fire, our author, after proving that combustible materials would not burn in the mineral regions, then says, that suppose they were to burn, this would be "incapable of forming a heat even equal to that of our common furnaces, as Mr Dolomieu has clearly shown to be the case with respect to volcanic heat." The place to which he alludes, I believe to be that which I have quoted from the Journal de Physique (Part I. page 139) to which I here beg leave to refer the reader. After what I have already said, this subject will appear to be of little concern to me; but, it must be considered, that my object, in these answers, is not so much to justify the theory which I have given, as it is to remove that prejudice which, to those who are not master of chemical and mineral subjects, will naturally arise from the opinion or authority of a scientific man, and a chemist; therefore, I think it my business to show how much he has misconceived the matter which he treats of, and how much he misunderstands the subject of my theory.

Mr Dolomieu alleges that the volcanic fire operates in the melting of bodies, not by the intensity of its heat, which is the means employed by us in our operations, but in the long continuance of its action. But in that proposition, this philosopher is merely giving us his opinion; and, this opinion our author mistakes, I suppose, for the fact on which that opinion had been (perhaps reasonably) founded. The reader will see, in the place quoted, or in the avant-propos to his Mémoire sur les Iles Ponces, the fact to be this; That the Chevalier Dolomieu finds those bodies which we either cannot melt in our fires, or which we cannot melt without changing them by calcination and vitrification, he finds, I say, these substances had actually been melted with his lavas; he also finds those substances, which are necessarily dissipated in our fires, to have been retained in those melted mineral substances. Had our author quoted the text, instead of giving us his own interpretation, he could not have offered a stronger confirmation of my theory; which certainly is not concerned with the particular intensity of volcanic fire, and far less with what may be the opinion of any naturalist with regard to that intensity, but only with the efficacy of that volcanic heat for the melting of mineral substances. Now this efficacy of volcanic fire, so far as we are to found upon the authority given on this occasion, is clearly confirmed by the observations of a most intelligent mineralist, and one who is actually a patron of the opposite theory to that which I have given. This being the state of the case, Must I not conclude, that our author has misunderstood the subject, and that he has been led to give a mutilated opinion of Mr Dolomieu, in order to refute my theory, when either the entire opinion, or the facts on which the opinion had been founded, would have confirmed it?

I have thus endeavoured to put in its true light a species of reasoning, which, while it assumes the air and form of that inductive train of thought employed by men of science for the investigation of nature, is only fit to mislead the unwary, and, when closely examined, will appear to be inconsequential or unfounded. How mortifying then to find, that one may be employed almost a lifetime in generalising the phenomena of nature, or in gathering an infinity of evidence for the forming of a theory, and that the consequence of this shall only be to give offence, and to receive reproach from those who see not things in the same light!—While man has to learn, mankind must have different opinions. It is the prerogative of man to form opinions; these indeed are often, commonly I may say, erroneous; but they are commonly corrected, and it is thus that truth in general is made to appear.

I wrote a general Theory for the inspection of philosophers, who doubtless will point out its errors; but this requires the study of nature, which is not the work of a day; and, in this political age, the study of nature seems to be but little pursued by our philosophers. In the mean time, there are, on the one hand, sceptical philosophers, who think there is nothing certain in nature, because there is misconception in the mind of man; on the other hand, there are many credulous amateurs, who go to nature to be entertained as we go to see a pantomime: But there are also superficial reasoning men, who think themselves qualified to write on subjects on which they may have read in books,—subjects which they may have seen in cabinets, and which, perhaps, they have just learned to name; without truly knowing what they see, they think they know those regions of the earth which never can be seen; and they judge of the great operations of the mineral kingdom, from having kindled a fire, and looked into the bottom of a little crucible.

In the Theory of the Earth which was published, I was anxious to warn the reader against the notion that subterraneous heat and fusion could be compared with that which we induce by our chemical operations on mineral substances here upon the surface of the earth; yet, notwithstanding all the precaution I had taken, our author has bestowed four quarto pages in proving to me, that our fires have an effect upon mineral substances different from that of the subterraneous power which I would employ.

He then sets about combining metals with sulphur in the moist way, as if that were any more to his purpose than is the making of a stalactite for the explanation of marble. Silver and lead may be sulphurated, as he says, with hepatic gas; but, Has the sulphurated solid ores of those metals, and that of iron, been formed in the moist way, as in some measure they may be by the fusion of our fires? But, even suppose that this were the case, Could that explain a thousand other appearances which are inconsistent with the operation of water? We see aerated lead dissolved in the excavations of our mines, and again concreted by the separation of the evaporated solvent, in like manner as stalactical concretions are made of calcareous earth; but, so far from explaining mineral appearances, as having had their concretions formed in the same manner, here is the most convincing argument against it; for, among the infinite variety of mineral productions which we find in nature, Why does no other example of aqueous concretion ever occur upon the surface of the earth except those which we understand so well, and which we therefore know cannot be performed in the bodies of strata not exposed to the evaporation of the solvent, a circumstance which is necessary.

I have given a very remarkable example of mineral fusion, in reguline manganese, (as the reader will see in page 68.) It is not that this example is more to the purpose of my theory than what may be found in every species of stone; but this example speaks so immediately to the common sense of mankind, (who are often convinced by a general resemblance of things, when they may not see the force of demonstration from an abstract principle) that I thought it deserved a place on that account, as well as being a curious example, But more particularly to my antagonist, who has been pleased (very improperly indeed) to try some part of my theory in the fire, here is an example which should have been absolutely in point, and without any manner of exception:—Has he acknowledged this?—No; he has, on the contrary, endeavoured to set this very example aside.

On this occasion, he says, "Manganese has been found in a reguline state by M. de la Peyrouse, and in small grains, as when produced by fire. True; but it was mixed with a large quantity of iron, which is often, found in that form without any suspicion of fusion. A fire capable of melting quartz might surely produce it in larger masses." We have here a kind of two arguments, for removing the effect of this example; and I shall consider them separately.

The first of these is, the not being suspected of having been in fusion; now, if this were to be admitted as an argument against the igneous origin of stony substances, it might have superseded the adducing of any other, for it is applicable perhaps to every mineral; but we must here examine the case more minutely.

This argument, of the manganese being in a mine of iron, if I understand it rightly, amounts to this, that, as iron ore is not suspected of having been melted, therefore, we should doubt the manganese having been so. If this be our author's meaning, it is not the fair conclusion which the case admits of; for, so far as the manganese appears evidently to have been in a melted state, the iron ore should be suspected of having been also in fusion, were there no other evidence of that fact. In science, however, it is not suspicion that should be employed in physical investigation; the question at present is; If the phenomena of the case correspond to the conclusion which the intelligent mineralist, who examined them, has formed? and, to this question, our author gives no direct answer. He says, iron is often found in that form without any suspicion of fusion. This is what I am now to answer.

The form in which the manganese appears is one of the strongest proofs of those masses having been in fusion; and, if iron should ever be found in that form, it must give the same proof of mineral fusion as this example of manganese; let us then see the nature of this evidence. The form of the manganese is that of a fluid body collecting itself into a spherical figure by the cohesion or attraction of its particles, so far as may be admitted by other circumstances; but, being here refilled by the solid part on which it rests, this spherical body is flattened by the gravitation of its substance. Now here is a regular form, which demonstrates the masses to have been in the state of fusion; for, there is no other way in which that form of those reguline masses could have been induced.

There now remains to be considered what our author has observed respecting the intensity of the fire and size of the masses. "A fire capable of melting quartz might surely produce it (meaning the manganese) in larger masses." M. de la Peyrouse says, that those masses were in all respects as if formed by art, only much larger, as the powers of nature exceed those of our laboratories. What then is it that is here meant to be disputed? We are comparing the operation of nature and that of art, and these are to be judged of by the product which we examine; but the quantity, in this case, or the size of the masses, makes no part of the evidence, and therefore is here most improperly mentioned by our author. With regard again to the nature of the fire by which the fusion had been produced, he is much mistaken if he imagines that the reduction of the reguline or metallic manganese depends upon the intensity of the heat; it depends upon circumstances proper for the separation of the oxygenating principle from the calx, in like manner as the calcination of calcareous spar must depend upon circumstances proper for allowing the separation of the carbonic acid or fixed air.

But do not let us lose sight of our proper subject, by examining things foreign or not so immediately to the purpose. We are only inquiring if those flattened spheres of native manganese had been formed by water, or if it were by fusion; for, our author agrees that there is no other way. Why then does he endeavour to evade giving a direct answer, and fly away to consider the quantity of the product, as if that had any thing to do with, the question, or as if that quantity were not sufficient, neither of which is the case. In short, our author's whole observation, on this occasion, looks as if he were willing to destroy, by insinuation, the force of an argument which proves the theory of mineral fusion; and that he wishes to render doubtful, by a species of sophistry, what in fair reasoning he cannot deny.

Our author has written upon the subject of phlogiston; one would suppose that he should be well acquainted with inflammable bodies at least; let us see then what he has to observe upon that subject. He quotes from my Theory, that spar, quartz, pyrites, crystallised upon or near each other, and adhering to coal, or mixed with bitumen, etc. are found; circumstances that cannot be explained in the hypothesis of solution in the moist way.—He then answers;—"Not exactly, nor with certainty; which is not wonderful: But they are still less explicable in the hypothesis of dry solution, as must be apparent from what has been already said. How coal, an infusible substance, could be spread into strata by mere heat, is to me incomprehensible."—It is only upon the last sentence that I am here to remark: This, I believe, will be a sufficient specimen of our author's understanding, with regard at least to my Theory which he is here examining.

The reader will see what I have said upon the subject of coal, by turning back to the second section of the preceding chapter. I had given almost three quarto pages upon that subject, endeavouring to explain how all the different degrees of infusibility were produced, by means of heat and distillation, in strata which had been originally more or less oily, bituminous, and fusible; and now our author says, that it is incomprehensible to him, how coal, an infusible substance, could be spread into strata by mere heat.—So it truly may, either to him or to any other person; but, it appears to me almost as incomprehensible, how a person of common understanding should read my Dissertation, and impute to it a thing so contrary to its doctrine.

Nothing can better illustrate the misconceived view that our author seems to have taken of the two opposite theories, (i. e. of consolidation by means of heat, and by means of water alone,) than his observation upon the case of mineral alkali. To that irrefragable argument (which Dr Black suggested) in proof of this substance having been in a state of fusion in the mineral regions, our author makes the following reply; "What then will our author say of the vast masses of this salt which are found with their full quantity of water of crystallization?"—There is in this proposition, insignificant as it may seem, a confusion of ideas, which it certainly cannot be thought worth while to investigate; but, so far as the doctrine of the aqueous theory may be considered as here concerned, it will be proper that I should give some answer to the question so triumphantly put to me.

Our author is in a mistake in supposing that Dr Black had written any thing upon the subject; he had only suggested the argument of this example of mineral alkali to me, as I have mentioned; and, the use I made of that argument was to corroborate the example I had given of sal gem. If, therefore, our author does not deny the inference from the state of that mineral alkali, his observation upon it must refer to something which this other example of his is to prove on the opposite side, or to support the aqueous instead of the igneous theory; and, this is a subject which I am always willing to examine in the most impartial manner, having a desire to know the true effect of aqueous solution in the consolidation of mineral bodies, and having no objection to allow it any thing which it can possibly produce, although denying that it can do every thing, as many mineralists seem to think.

The question, with regard to this example of our author's of a mineral alkali with its water of crystallization, must be this, Whether those saline bodies had been concreted by the evaporation of the aqueous solvent with which they had been introduced, or by the congelation of that saline substance from a fluid state of fusion; for, surely, we are not to suppose those bodies to have been created in the place and state in which we find them. With regard to the evaporation or separation of the aqueous solvent, this may be easily conceived according to the igneous theory; but, the aqueous theory has not any means for the producing of that effect in the mineral regions, which is the only place we are here concerned with. Therefore, this example of a concreted body of salt, whatever it may prove in other respects, can neither diminish the evidence of my Theory with regard to the igneous origin of stony substances, nor can it contribute to support the opposite supposition of an aqueous origin to them.

But to show how little reason our author had for exulting in that question which he so confidently proposed in order to defeat my argument, let us consider this matter a little farther. I will for a moment allow the aqueous theory to have the means for separating the water from the saline solution, and thus to concrete the saline substance in the bowels of the earth; this concretion then is to be examined with a view to investigate the last state of this body, which is to inform us with regard to those mineral operations. But, our author has not mentioned whether those masses appear to have been crystallised from the aqueous solution, or if they appear to have been congealed from the melted state of their aqueous fusion.—Has he ever thought of this? Now this is so material a point in the view with which that example has been held out to us, that, without showing that this salt had crystallised from the solution, he has no right to employ it as an example; and if, on the other hand, it should appear to have simply congealed from the state of aqueous fusion, then, instead of answering the purpose for which our author gave it, it would refute his supposition, as certainly as the example which I have given.

So far I have reasoned upon the supposition of this alkali, with its water of crystallization, being truly a mineral concretion; but, I see no authority for such a supposition: It certainly may be otherwise; and, in that case, our author would have no more right to give it as an example in opposition to Dr Black's argument, than he would have to give the crystallization of sea-salt, on Turk's Island, in opposition to the example which I had given, of the salt rock, at Northwych in Cheshire, having been in the state of fusion.

It certainly was incumbent on our author to have informed us, if those masses of salt were found in, what may be properly termed, their mineral state; or, if the state in which they are found at present had been produced by the influences of the atmosphere, transforming that saline substance from its mineral state, as happens upon so many other occasions; I am inclined to suspect that this last is truly the case. It may be thought illiberal in me to suppose a natural philosopher thus holding out an example that could only serve to lead us into error, or to mislead our judgment with regard to those two theories which is the subject of consideration. This certainly would be the case, almost on any other occasion; but, when I find every argument and example, employed in this dissertation, to be either unfounded or misjudged, Whether am I to conclude our author, on this occasion, to be consistent with himself, or not?

I have but one article more to observe upon. I had given, as I thought, a kind of demonstration, from the internal evidence of the stone, that granite had been in the fluid state of fusion, and had concreted by crystallization and congelation from that melted state. This no doubt must be a stumbling block to those who maintain that granite mountains are the primitive parts of our earth; and who, like our author, suppose that "things may have been originally, as at present, in a solid state." It must also be a great, if not an invincible obstacle in the way of the aqueous theory, which thus endeavours to explain those granite veins that are found traversing strata, and therefore necessarily of a posterior formation.

To remove that obstacle in the way of the aqueous theory, or to carry that theory over the obstacle which he cannot remove, our author undertakes to refute my theory with regard to the igneous origin of stony substances, by giving an example of granite formed upon the surface of the earth by means of water, or in what is called the moist way; and he closes his Dissertation with this example as an experimentum crucis. It is therefore necessary that I take this demonstration of our author into particular consideration; for, surely, independent of our controversy, which is perhaps of little moment, here is the most interesting experiment, as it is announced, that mineralogy could be enriched with.

"To close this controversy," says our author, "I shall only add, that granite, recently formed in the moist way, has been frequently found."—Of that remarkable event, however, he has selected only one example. This is to be found upon the Oder; and the authority upon which our author has given it, is that of Lasius Hartz.

The formation of a granite stone, from granite sand, by means of water, is inconsistent with our chemical knowledge of those mineral substances which constitute that stone; it is repugnant to the phenomena which appear from the inspection of the natural bodies of this kind; and it is directly contrary to the universal experience in granite countries, where, instead of any thing concreting, every thing is going into decay, from the loose stones and sand of granite, to the solid rock and mountains which are always in a state of degradation. Therefore, to have any credit given to such a story, would require the most scientific evidence in its favour. Now, in order that others may judge whether this has been the case in this example, I will transcribe what our author has said upon the subject; and then I will give the view in which it appears to me.

He says, "a mole having been constructed in the Oder in the year 1723, 350 feet long, 54 feet in height, 144 feet broad at bottom, and 54 at the top, its sides only were granite, without any other cement than moss; the middle space was entirely filled with granite sand. In a short time this concreted into a substance so compact as to be impenetrable by water."—Here is an example, according to our author, of granite formed in the moist way. But now, I must ask to see the evidence of that fact; for, from what our author has told us, I do not even see reason to conclude that there was the least concretion, or any stone formed at all. A body of sand will be so compacted as to be impenetrable by water, with the introduction of a very little mud, and without any degree of concretion; muddy water, indeed, cannot be made to pass through such a body without compacting it so; and this every body finds, to their cost, who have attempted to make a filter of that kind.

But I shall suppose Lasius has informed our author that there had been a petrifaction in this case; and, before I admit this example of the formation of granite, I must ask what sort of a granite it was;—whether of two, three, or four ingredients; and, how these were disposed. If, again, it were not properly a granite, but a stone formed of granite sand, What is the cementing substance?—Is it quartz, felt-spar, mica, or schorl?—or, Was it calcareous? If our author knows any thing about these necessary questions, Why has he not informed us, as minutely as he has done with regard to the dimensions of the mole, with which we certainly are less concerned? If, again, he knows no more about the matter than what he has informed us of, he must have strangely imposed upon himself, to suppose that he was giving us an example of the formation of granite in the moist way, when he has only described an effectual way of retaining water, by means of sand and mud.

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