"Basaltic pillars, in general, bid defiance to decay," &c. He goes on to deny every step of the degradation of land, by which it is wasted, carried into the sea, and spread out over its bottom, though all these are necessary postulata in his theory of the formation of coal. One can be at no loss about estimating the value of a system, in which such gross inconsistencies make a necessary part.
145. The quantity of hornblende and siliceous schistus, necessary to be decomposed, in order to produce the coal strata presently existing, is enormous, and would lead to an estimate of what is worn away from the primeval mountains, far exceeding any thing that Dr Hutton has supposed. It is true, that Mr Kirwan, never at all embarrassed about preserving a similitude between nature as she is now, and as she was heretofore, lays it down, that the part of the primeval mountains which is worn away, contained much more carbon than the part which is left behind. This, however, is an arbitrary supposition; and since, in this system, such suppositions are so easily admitted, why may we not conceive, in the primeval mountains, a more copious source of carbonic matter than hornblende or siliceous schistus? We have but to imagine, that the diamond existed among these mountains in such abundance, as to constitute large rocks. This stone being made up of pure, or highly concentrated carbon, the adamantine summits of a single ridge, by their decomposition, might afford a carbonic basis, sufficient for the coal beds of all the surrounding plains.
146. We may also object to Mr Kirwan, that the siliceous part of the mountains has not been chemically dissolved; it has been only abraded and worn away. Mechanical action has reduced the quartz to gravel and sand, but has not produced on it any chemical change. The carbon, therefore, could not be let loose. Experiment, indeed, might be employed, to determine whether the siliceous matter of the secondary, and of the primary strata contains this substance in the same proportion.
Again, a more fatal symptom can hardly be imagined in any theory, than that, when the circumstances of the phenomena to be explained are a little changed, the theory is under the necessity of changing a great deal. Now, this is what happens to Mr Kirwan's theory, in the attempt made to explain by it the stratum of coal described in the Annales de Chimie,[56] as cutting a mountain of argillaceous strata in two, at about three-fourths of its height. This stratum, Mr Kirwan says, must have been formed by transudation from the superior part of the mountain,[57] Besides that this is a gratuitous supposition of a thing, without example, it involves in it an absurdity, which becomes evident the moment the question is asked, What occupied the place of the coal-bed before the transudation from the upper part of the mountain? Has the liquid coal, as it percolated through the upper strata, expelled any substance from the place it now occupies? or has it been powerful enough to raise up, or to float, as it were, the upper part of the mountain?
[56] Tom. xi. p. 272.
[57] Geol. Essays, p. 338.
The situation of this bed of coal is not singular, and its formation is easily explained on Dr Hutton's theory. It is part of a stratum of coal, which has been deposited, like all others, at the bottom of the sea; from whence certain causes, of very general operation, have raised it up, together with the attending strata: these strata have since been all cut down, and worn away by the operations of the surface; and the mountain, with the coal stratum in the middle of it, is a part of them which has been left behind. There is no wonder, that a coal stratum should be found alternating with others, in a mountain, any more than in the bowels of the earth, and no more need of a separate explanation.[58]
[58] This stratum of coal, which is described by Hassenfratz, is remarkable for being in a mountain which rests immediately on primary schistus and granite.
147. After all, it may be asked, for what purpose is it that so many incongruous and ill supported hypotheses are thus piled on one another? is it only to avoid ascribing the carbonic and bituminous matter of coal to a substance in which we know with certainty that such matter resides in great abundance, in order to derive it from other substances, in which a subtle analysis has shown, that it exists in a very small proportion? Such reasoning is so great a trespass on every principle of common sense, not to say of sound philosophy, that, to bestow any time on the refutation of it, is, in some degree, to fall under the same censure.