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.