THE EDINBURGH NEW PHILOSOPHICAL JOURNAL. On the Diluvial Theory, and on the Origin of the Valleys of Auvergne. By C. DAUBENY, M. D., F. R. S., Professor of Chemistry in the University of Oxford, &c. &c. In a Letter to Professor JAMESON. DEAR SIR, It is now more than ten years since I published in your Journal a brief and general account of the volcanos of Auvergne, which, in spite of its many imperfections, of which no one can be more sensible than its author, will perhaps be allowed the humble merit of having contributed to direct the attention of British naturalists to this interesting field of continental geology. Since the appearance of my memoir, Auvergne has been visited by Mr Scrope, Professor Buckland, Messrs Lyell and Murchison, and sundry other scientific travellers; and through their collective exertions such a mass of information has been brought together, with reference to the phenomena therein exhibited, that there is probably no volcanic district in the world now more fully explored, nor perhaps any country out of Great Britain with the geological relations of which we are more familiar. You will easily believe, that I have been far more gratified at seeing so many distinguished naturalists following in my track, than mortified at finding them sometimes arrive at conclusions different from my own; and that, under this feeling, I should be the more inclined, even where my confidence in my original views remained unshaken, to waive controversy, and JANUARY-MARCH 1831. wait with patience for the slow but sure judgment of the public, to pronounce upon the points at issue between us. I have been induced, however, to depart from this my original purpose, chiefly in consequence of the perusal of my friend Mr Lyell's work, entitled, "Principles of Geology;" not from any ambition on my part to contend generally against the views he has put forth, but from an anxiety to explain myself more fully than I have hitherto had occasion to do on a question much agitated in his volume, I mean the causes to which the excavation of valleys is to be referred-seeing that the nomenclature, as well as to a certain degree the theoretical views I have adopted in my Description of Volcanos *, with reference to this subject, are those of writers to whom the author alluded to seems directly opposed. Nevertheless, I am inclined to think that the discrepancy between his opinions and my own on this particular point, reduces itself almost to a question of degree; for I observe that in more than one passage of his work, the probability of extensive floods having from time to time occurred in consequence of the bursting of vast lakes, is distinctly admitted, and it can hardly be doubted, but that from such catastrophes would result effects of a similar nature to those commonly ascribed to that diluvial action so insisted on by geologists of a different school. It is, however, no less true, that, in accounting for this class of phenomena, much greater stress is laid in his treatise on the long continued operation of causes of daily occurrence, than on the consequences of such occasional catastrophes, and that many might rise from its perusal under an impression, that geologists of the present day, who take a different view of such phenomena, still adhere to the doctrine maintained by their predecessors, who, to use Mr Lyell's words, supposed "that the monuments which they endeavoured to decipher relate to a period when the physical constitution of the earth differed entirely from the present, and that even after the creation of living beings there have been causes in action, distinct in kind or degree from those forming a part of the present economy of na * A Description of Active and Extinct Volcanos. By Charles Daubeny, M. D. F. R.S. &c. &c. 8vo. London, 1826. Such a notion, indeed, would be quite at variance with the general tenor of my work on Volcanos, the express object of which was to shew, that the same causes which produce volcanic phenomena at the present moment, operating at some former period on a greater scale, but always agreeably to the same system, have had an important share in preparing the earth's surface for the abode of the existing races of animals *. It is, however, true, that certain writers, whose opinions I have quoted rather than adopted at the commencement of the work in question, embarrassed by the difficulties they encountered in their attempts to explain the phenomena alluded to by the operation of present agents, and perhaps not sufficiently considering the still greater objections to the supposition of a change having taken place in the course of nature, may have laid themselves open to Mr Lyell's criticisms, by adopting the opinions of carlier naturalists with respect to a want of conformity in the physical constitution of the earth during ancient and modern times. Hence, in order to enable others to form a candid estimate of the comparative merits of the views of Mr Lyell with respect to the excavation of valleys, and those of the Diluvianists, it seems important that we should do away with the prejudice that would operate against the latter, from associating them with this hypothesis; and it may therefore be worth while to shew that no necessary connexion exists between the two, but that all the postulates of the diluvial theory may be resolved into the operation of known agents, acting according to laws at present recognised +. It will doubtless be considered as so far favourable to this system, if it can be proved, that it supposes no other catastrophes or revolutions to have taken place, than such as would na Similar, too, have been the conclusions to which I have since been led by my researches on the presence of iodine and bromine in the salt-springs of this country, as it appears from the results I have obtained, that the constituents of the earliest seas, such for instance as existed at the time of the transition formation, were precisely the same as those of the present day, and, consequently, that the laws of nature in this respect have continued from the first unchanged. See Phil. Trans. for 1830. + Having written the greater part of this letter whilst on the continent, I was not aware that Mr Conybeare had already entered a protest, in the Annals of Philosophy for October last, against the notion, that in the diluvial theory the operation of a different system of causes is necessarily implied. turally arise, agreeably to existing laws, from events which we believe on independent grounds to have taken place, and which the very persons most opposed to aqueous inundations are often the foremost to contend for. I do not here allude to the occasional bursting of lakes, which, as we have already seen, may in particular situations account for some of the phenomena under consideration; because it is impossible to imagine such local catastrophes to have occurred in all the spots where indications of diluvial action are supposed to present themselves; but I maintain, that there is a probability of floods having taken place, more considerable in point of extent, more generally diffused over the earth, and therefore more capable of modifying the character of its surface, than those supposed by Mr Lyell to have resulted from the local causes he has assigned. The same sudden rise of an extensive body of water, which would in the present day be produced by the throwing up of a chain of hills in the midst of the Mediterranean, might, as it appears to me, have resulted from such events as the elevation of the Alps, the Pyrenees, or the volcanic chain of the Andes, the two former of which we know to be surrounded by immense sedimentary deposits, which may have arisen from the aqueous inundations that were the immediate consequences of their rise. It is indeed only necessary for such a supposition, that the catastrophe should have occurred in the vicinity of large lakes or seas, and that it should have been brought about in a short period of time; and the latter, although I am aware it is contrary to the opinion of Mr Lyell, is the doctrine, I believe, of most of the other supporters of the elevation theory, and especially of Monsieur Elie de Beaumont, whose recent conclusions, with regard to the successive rise of several chains of mountains in different parts of the globe, can hardly be embraced in their full extent, except by those who are willing to admit, as a consequence, the occurrence of several extensive, if not universal, deluges. The doctrine in question has the further advantage of rendering the accounts of such catastrophes, which are handed down to us on the authority both of history and tradition, consistent with probability, instead of opposed to it; in harmony with scientific research, instead of involving, as Voltaire rashly asserted, a physical impossibility; and thus, if not directly confirming the Mosaic history on this particular point, removing at least those obstacles to its reception that might exist, if we considered the event related as out of the course of nature, and only to be explained by the instrumentality of causes unknown to us at present, and which had disappeared without leaving any traces of their existence behind them. It is, however, far from my intention to excite a prejudice against any attempt that may be made to explain the phenomena in question on different principles, by insinuating the inconsistency of such other conclusions with the Mosaic records. Nothing, I conceive, can be more unfair than such a mode of attack, or more likely to do injury to the cause it professes to serve. But though a doctrine in science may be true, although involving conclusions that cannot be reconciled, at the time, to the statements of Scripture, it will be allowed to be somewhat more probable when in conformity to them; and, in the present instance, considering, as I should wish to do, the question in the same light as one in which the veracity of profane history alone was at stake*, we shall be inclined to regard it as a recommendation to the view taken, that it confirms and accounts for an event which has reached us through such a variety of distinct channels, that few probably would feel themselves justified in rejecting the fact of its occurrence, however much they may be disposed to differ as to its details. It is not, however, my intention to controvert the opinions of Mr Lyell on this point, but only to show that more might be attributed to the effect of sudden catastrophes than he appears * I make this concession, in order to prevent the possibility of my being accused of having mixed up a question of theology with one of science. The mode in which the deluge might have taken place, the causes which produced it, its universality, and other points of the same description, cannot, I admit, be decided by the words of Scripture, the writers of which describe merely appearances and effects, and need not be supposed to have been enlightened with respect to their physical causes. This, however, is quite foreign from the question, whether, in balancing the rival pretensions of two scientific theories, we should be justified in throwing out of the scale the evidence derived from a fact so circumstantially related in the earliest of known records, and confirmed, in the main, by the traditions of other nations? |