In forming a geological theory, the general construction of this earth, and the materials of which it is composed, are such visible objects, and so evident to those who will take the pains to examine nature, that here is a subject in which there cannot be any doubt or difference of opinion. Neither can there be any dispute concerning the place and situation of mass when it was first formed or composed; for, this is clearly proved, from every concomitant circumstance, to have been at the bottom of the sea. The only question in this case, that can be made, is, How that mass comes now to be a solid body, and above the surface of the sea in which it had been formed?
With regard to the last, the opinions of philosophers have been so dissonant, so vague, and so unreasonable, as to draw to no conclusion. Some suppose the land to be discovered by the gradual retreat of the ocean, without proposing to explain to us from whence had come the known materials of a former earth, which compose the highest summits of the mountains in the highest continents of the earth. Others suppose the whole of a former earth to have subsided below the bottom even of the present sea, and together with it all the water of the former sea, from above the summits of the present mountains, which had then been at the bottom of the former sea. The placing of the bottom of the sea, or any part of it, in the atmosphere so as to be dry land, is no doubt a great operation to be performed, and a difficult task to be explained; but this is only an argument the more for philosophers to agree in adopting the most reasonable means.
But though philosophers differ so widely in that point, this is not the case with regard to the concretion of mineral bodies; here mineralists seem to be almost all of one mind, at the same time without any reason, at least, without any other reason than that false analogy which they have inconsiderately formed from the operations of the surface of this earth. This great misunderstanding of mineralists has such an extensive and baneful effect in the judging of geological theories, that it will be proper here to explain how that has happened, and to show the necessity of correcting that erroneous principle before any just opinion can be formed upon the subject.
Fire and water are two great agents in the system of this earth; it is therefore most natural to look for the operation of those agents in the changes which are made on bodies in the mineral regions; and as the consolidated state of those bodies, which had been collected at the bottom of the sea, may have been supposed to be induced either by fusion, or by the concretion from a solution, we are to consider how far natural appearance lead to the conclusion of the one or other of those two different operations. Here, no doubt, we are to reason analogically from the known power and effects of those great agents; but, we must take care not to reason from a false analogy, by misunderstanding the circumstances of the case, or not attending to the necessary conditions in which those agents act.—We must not conclude that fire cannot burn in the mineral regions because our fires require the ventilation of the atmosphere; for, besides the actual exigence of mineral fire being a notorious matter of fact, we know that much more powerful means may be employed by nature, for that mineral purpose of exciting heat, than those which we practise.—We must not conclude that mineral marble is formed in the same manner as we see a similar stony substance produced upon the surface of the earth, unless we should have reason to suppose the analogy to be complete. But, this is the very error into which mineral philosophers have fallen; and this is the subject which I am now to endeavour to illustrate.
The manner in which those philosophers have deceived themselves when reasoning upon the subject of mineral concretion, is this: They see, that by means of water a stony substance is produced; and, this stony body so much resembles mineral marble as to be hardly distinguishable in certain cases. These mineral philosophers then, reasoning in the manner of the vulgar, or without analysing the subject to its principle, naturally attribute the formation of the mineral marble to a cause of the same sort; and, the mineral marble being found so intimately connected with all other mineral bodies, we must necessarily conclude, in reasoning according to the soundest principles, that all those different substances had been concreted in the same manner. Thus, having once departed one step from the path of just investigation, our physical science is necessarily bewildered in the labyrinth of error. Let us then, in re-examining our data, point out where lies that first devious step which had been impregnated with fixed air, or carbonic acid gas, (as it is called), dissolves a certain portion of mild calcareous earth or marble; consequently such acidulated water, that is, water impregnated with this gas, will, by filtrating through calcareous substances, become saturated with that solution of marble; and, this solution is what is called a petrifying water. When this solution is exposed to the action of the atmosphere, the acid gas, by means of which the stony substance is dissolved, evaporates from the solution, in having a stronger attraction for the atmospheric air; it is then that the marble, or calcareous substance, concretes and crystallises, separating from the water in a sparry state, and forming a very solid stone by the successive accretion from the solution, as it comes to be exposed to the influence of the atmosphere in flowing over the accumulating body. Here is the source of their delusion; for, they do not distinguish properly the case of this solution of a stony substance concreting by means of the separation of its solvent, and the case of such a solution being in a place where that necessary condition cannot be supposed to exist; such as, e.g., the interstices among the particles of sand, clay, etc. deposited at the bottom of the sea, and accumulated in immense stratified masses.
No example can better illustrate how pernicious it is to science to have admitted a false principle, on which a chain of reasoning is to proceed in forming a theory. Mineral philosophers have founded their theory upon that deceitful analogy, which they had concluded between the stalactical concretions of petrifying waters and the marble formed in the mineral regions; thus, blinded by prejudice, they shut the door against the clearest evidence; and it is most difficult to make them see the error of their principle. But this is not to be wondered at, when we consider how few among philosophising men remount to the first principles of their theory; and, unless they shall thus remount to that first step, in which the concreting operation of a dissolved stony substance is supposed to take place without the necessary conditions for the petrifying operation, it is impossible to be convinced that their theory, thus formed with regard to mineral concretion, is merely supposition, and has no foundation in matter of fact from whence it should proceed.
But this is not all; for, even supposing their theory to be well founded and just, it is plainly contradicted by natural appearances. According to that theory of aqueous consolidation, all the stratified bodies, of which this earth in general consists, should be found in the natural order of their regular formation; but, instead of this, they are found every where disturbed in that order more or less; in many places this order and regularity is so disturbed as hardly to be acknowledged; in most places we find those stratified bodies broken, dislocated, and contorted, and this aqueous theory of mineralists has neither the means for attaining that end, were it required in their theory, nor have they any such purpose in their theory, were that end attainable by the means which they employ. Thus blinded by the prejudice of a false analogy, they do not even endeavour to gratify the human understanding (which naturally goes in quest of wisdom and design) by forming a hypothetical or specious theory of the mineral system; and they only amuse themselves with the supposition of an unknown operation of water for the explanation of their cabinet specimens, a supposition altogether ineffectual for the purpose of forming a habitable earth, and a supposition which is certainly contradicted by every natural appearance.
Thus, in examining geological and mineralogical theories, I am laid under the disagreeable necessity of pointing out the errors of physical principles which are assumed, the prejudices of theoretical opinions which have been received, and the misconceived notions which philosophers entertain with regard to the system of nature, in which may be perceived no ineffectual operation, nor any destructive intention, but the wise and benevolent purpose of preserving the present order of this world. But, though thus misled with regard to the cause of things, naturalists are every where making interesting observations in the mineral kingdom, I shall therefore avail myself of that instructive information, for the confirmation of my theory.
It may now be proper to consider what must be required, in order to have a geological and mineral theory established upon scientific principles, or on such grounds as must give conviction to those who will examine the subject; for, unless we may clearly see that there are means for attaining that desirable end, few philosophers will be persuaded to pursue this branch of knowledge.
A theory is nothing but the generalization of particular facts; and, in a theory of the earth, those facts must be taken from the observations of natural history. Nature is considered as absolutely true; no error or contradiction can be found in nature. For, if such contradiction were truly found, if the stone, for example, which fell to day were to rise again to-morrow, there would be an end of natural philosophy, our principles would fail, and we would no longer investigate the rules of nature from our observations.