NOTE [III.] On M. HUMBOLDT's Theory of Rocks. In the " Geognostical Essay on the Superposition of Rocks in both Hemispheres," this Herculean explorer, 66 "Emensus longi claviger orbis iter," has embodied, not only the observations of his own extraordinary personal experience, but that also of all the ablest and most celebrated writers of this age of Geology. The professed object of his elaborate treatise, is, "to trace the "Elements of Geognostic Philosophy, as far as regards "the study of the superposition of rocks." His work, he states, "includes nearly the whole of positive geognosy," (as opposed to " hypothetic geology"); and "he endeavours, at the same time that he presents the detail of "the phenomena of the superposition, or tabular arrange-, "ment, of formations, to generalise the ideas respecting "them with the great questions in Natural Philosophy 3: -"Positive or True geognosy, (he says,) ought to present a chain of facts well observed, and judiciously compared together :-it describes the exterior crust of our globe "such as it exists in our days.—This science, (he continues,) has no less certainty than the physical descriptive sciences in general." By means of it, "the "order of superposition, and the relative age of rocks, are "facts susceptible of being determined, like the structure of a plant: on the contrary, whatever relates to the 66 33 66 " 1 Page 42. 2 Page 8. 3 Pref. p. v. vi. * Page 6. "ancient state of our planet; to those fluids which, it is said, held all mineral substances in solution; to those seas which have covered the summits of the Cordilleras, “and have afterwards disappeared; is as uncertain, as thę "formation of the atmosphere of the planets, as the " various migrations of plants, or the origin of the different varieties of our species. Yet, the time is not very "remote, (he adds,) when geologists were occupied from "choice in the solution of these problems, and with this 66 1 fabulous period of the physical history of the earth 1." "The new doctrine of geogony, (he says,) has a tendency "to lean towards the idea of the liquefied masses ascending across the fissures from below upwards, whilst the ancient geogony (i. e. that of Werner, propounded four years " before by M. D'Aubuisson, and maintained by M. Hum"boldt himself in 18042,) explained every thing by pre ་ cipitations and movements in an opposite direction : positive geogony has profited by these discussions on "the igneous or neptunian origin of rocks; but it renders "the classification independent of geogonic results3.""I must confess, (he proceeds,) that these classifications, according to the various hypotheses which we form on the origin of things, appear to me not only vague and arbitrary, but also very injurious to the progress of a geognosy of position; they prejudge in too arbitrary and absolute a manner, what is at least extremely doubtful "."—" When the geognost has examined "the relations of position and composition, he has fulfilled "his task5" Here then we have, at last, a writer on geology altogether practical; who condemns, in the most express and in the strongest manner, every thing that is theoretical or 1 Page 5, 6. 2 See above, p. 10, note. 3 Page 414. hypothetical in discussions on the structure of the earth. His "geognosy" is only "a descriptive science" of the crust of our globe, as it now exists; not as it " 46 may be supposed to have been 1." The simple and actual matter of fact, is, avowedly, the exclusive object of his consideration and instruction; which is presented to our view under the compendious form, of a Tabular arrangement of formations observed in both Hemispheres. "Although in "the course of a laborious life, (says this indefatigable scrutinator,) I have had the pleasure of seeing a greater "extent of mountains than any other geognost, the little "I observed is lost in the great mass of facts which I "have undertaken to display. What is most important "in this treatise on formations, is derived from the com"bined efforts of my contemporaries. I wished to present "to my readers, in a concise manner, the whole of the "discoveries that have been made; and I thought I MIGHT ADD what is ONLY PROBABLE, to what appears to me completely verified. If I have attained the end pro"posed, the distinguished men, who, in Germany, France, England, Sweden, and Italy, have contributed "to enlarge the edifice of geognostic science, will recognise "in every page the results of their own labours." Yet, notwithstanding this emphatic disclaimer of all hypothesis, notwithstanding this determined advocacy of facts, and facts only, the "Geognostical Essay" is governed throughout by a masked theory; of which its eminent author appears to be hardly conscious, but of which the attentive reader will have caught some surmise from the reservation claimed by the author; " of adding what is only probable, (that is, in his own opinion) to what appears completely verified," and thus, of incorporating theory with the facts of his observation and experience. 66 This theory of probabilities, I shall now proceed to unmask; in order that we may be able to distinguish and ascertain exactly, how far his geognosy of fact is also a geognosy of hypothesis, and thus reveals itself to be only another variety of that Alchymical Geology, which has already been examined and exposed. It is not possible for any human mind, and especially for one so active and searching as M. Humboldt's, to be busily and earnestly engaged in contemplating the materials of the crust of this globe, their position and composition, without secretly viewing them under their relation of effects; and, however determined it may be to confine its attention to them as effects only, yet such is the moral construction of the intellect, that it cannot restrain itself from looking from them to the causes, and from an endeavour to restore the relation between the two. If those causes are known and manifest, it will naturally resort to them for guidance, and will rest on them for its own relief; if they are unknown, or latent, it will then strive to procure for itself the same relief, by assuming such others as appear to it the most probable. So it has happened with our celebrated geognost. He has rested, in his geognostic labours, on certain causes which he assumed as most probable, and (to use his own phrase,)" as points of repose for the mind1;" by, and in reference to which causes, he has exposed all his practical observations on the exterior crust of the globe. Those assumed causes constitute his theory, (a phrase, which may perhaps sound very strange to his ears ;) and they are these: 66 Having profited by the discussions on the igneous " and neptunian origin of rocks, M. Humboldt does not "hesitate to range himself on the side of those geognosts, "who rather conceive the formation of crystalline siliceous 1 Page 30.. 66 "(i. e. primitive) rocks by fire, than by an aqueous solu"tion:" thus taking his post, at the outset, on the vulcanian side, in the historical question of the MODE of primitive formations. Hence he intimates, that, "in the “first period of the world, the crust of the globe, strongly "heated in its interior, became fissured, and gave a high "temperature to the circumambient air; independently of a distribution of climates similar to those of the présent time—perhaps, anterior to the existence of a diversity of climates." Here, the absorbed geognost is suddenly and unconsciously borne away into a contemplation of that "fabulous period of the physical history of the earth,” which he condemns in all other geognostical writers, but which is nevertheless essentially inseparable from his own geognosy. 66 66 66 66 But, though he does not hesitate to ascribe the formation of the primitive siliceous rocks to igneous action, and though he speaks of the pretended neptunian origin of some rocks1, yet, he does not contest the ancient (aqueous) fluidity, or the softness, of the stony beds: a phenomenon, which he considers to be proved by the "fossil bodies, by the crystalline aspect of the masses, by "the rolled pebbles, or the fragments imbedded in the "transition (or fragmentary) and secondary rocks”—all which testify to him " the bottoms of the basins in which "the stony deposits have been formed3. 66 Now," in the long series of rocks (primitive and secondary), in this assemblage of monuments of different epochas, "M. Humboldt distinguishes, chiefly, three very striking phenomena; viz. the first dawn of organic life on the globe, the appearance of fragmentary rocks, and the catastrophe which has buried the ancient monocoty 66 66 |