tance of a quarter of a league.* The whole projected mass BOOK was computed to amount to 100,000 cubic feet; according XVIII. to Pallas it consisted of a bluish clay. The Growing, or Increasing Mountains, which are met with at the foot of Caucasus, near Bakow, and near the mouth of the river Kur, belong to the same class. They are produced by springs, which throw out a salt claggy mud; and in this manner hills above 400 feet high are formed.† Volcanoes themselves throw out, though with greater violence, substances dissolved in water. Those which crown the chain of the Andes, near the city of Quito, emit only a small portion of scoriæ, but an enormous quantity of water and clay, combined with carbon and sulphur. These examples may suffice to show, that the eruption of earthy substances in watery solution, far from being an insulated and unimportant phenomenon, forms even to this day one of the most remarkable sources of the changes which have taken place on the surface of the globe; and that in former ages it probably had a very great influence in the formation of our mountains. We think we may ascribe, if not to the same, at least to a similar cause, the origin of the coagulated rocks known under the name of Basalt. It is thus that all the elements of nature are armed for Conclusion. mutual destruction. What are those revolutions that we behold, in comparison of those which must have operated together in the creation of the world, and which perhaps are one day destined to accomplish its final destruction. May not those stars, those suns without number which guide the mariner in the midst of the pathless deep, be in a moment extinguished? May not this arch of the globe which supports us, give way beneath our feet? Is not the equilibrium of the seas liable to be subverted, and will not the foaming billows one day roll over these continents *Pallas, Voyage dans la Russie méridionale. Lerch, Voyages cités par Georgi, Description de la Russie, I. 114. BOOK which are at present covered with the monuments of human XVIII. industry? May not the earth approach too near to the sun, and be swallowed up by it like a drop in the ocean? May it not wander into those remote and dreary regions of space, where the solar heat is too feeble to support the principle of life? How frightful would it be to exist in the midst of these perfidious elements, in the bosom of this perishable universc, without the consoling thought of a supreme intelligence, that both checks and wields at will the formidable and blind powers of nature? It is only the belief in an order of things superior to matter, in a moral world, that can fortify us against the terrors by which our physical existence is every where assailed. BOOK XIX. Continuation of the Theory of Geography. View of Geological Systems, or Opinions regarding the Formation of the Globe. XIX. IN the course of this work, we have seen that the phy- BOOK sical geographer cannot refrain from connecting together certain facts, which frequently recur, and deducing from them general conclusions. He is even forced sometimes to present facts in an hypothetical manner, because observers have furnished him with their remarks under that form. But physical geography affirms nothing which is not established by experience. Systems of geology, on the contrary, have for their professed object to trace the progress of unknown revolutions, by the assistance of monuments which are often equivocal. The authors of such systems, in the absence of positive facts, do not scruple to call in the aid of analogy, and thus, by hypothesis after hypothesis, they analyze and recompound the vast globe of the earth, as if it were a piece of metal, which the chemist could fuse in his crucible. We shall endeavour to prove, that this pretended science, or speculative geology, promises no certain results, since it oversteps the evidence of facts, that is, since it deviates from the sure and beaten paths of physical geography. In the first place, the portion of the globe which is known to us, does not constitute, at the very utmost, the thousandth part of its entire mass. Our excavations do little more than scratch the surface of the earth; our geo Insufficien servations. BOOK logists have surveyed with attention scarcely the half of XIX. Europe, or the tenth part of America and Asia; the observations which have been made are extremely few; and cy of geo- yet unbounded scope has been given to speculation. We logical ob do not know whether the interior of the globe is composed of substances analogous to those occurring on its surface, or consists solely of a mass of sand; whether it contains within a central fire which continually burns, or a vast reservoir of primitive waters; or whether, finally, the globe. is only a hollow sphere, filled with air and vapours. As to these matters, we know nothing whatever, and can by no arguments, astronomical or physical, prove either the truth or the falsity of any of these opinions. In the vast and unexplored recesses of the globe, it is possible that there may lie concealed, agents so active and so powerful, that to them the various revolutions which the earth has undergone, may have been the work only of so many moments. As long as the interior of the globe remains unknown to us, the conclusion which we may draw from facts observed on the surface, can be no more than probable in reference to these facts; but whenever we attempt to combine the conclusions in order to form a general system, their uncertainty will clearly appear; for, opposite to a finite sum of probabilities, however strong we may suppose them, there shall arise an infinite sum of unknown terms, of which one alone may perhaps be sufficient to counterbalance all our probabilities. Value of It is in vain to compare geological hypotheses with those hypotheses made use of in astronomy, natural philosophy, and chein geology. mistry. The theory of attraction, for example, is purely and simply a mode of stating a fact furnished by observation; it is a formula for computing the known effects of certain unknown forces, as to the nature of which no opinion is expressed. But the authors of those philosophical poems, improperly called theories of the earth, will not confine themselves to the stating of facts; they have recourse to mere suppositions. But, what is more, even facts XIX. physic and in geology, however completely they have been established, BOOK cannot be expressed in mathematical terms; they are incapable of being subjected to calculation. We therefore apprehend that chemistry and physics, far from furnishing Abuse of arms to extend the empire of geology, must, on the con- chemistry. trary, disavow the premature and too general application that has been made of some theoretical principles, of which philosophers and chemists have availed themselves only in questions of doubtful speculation. Philosophy may admit, without complete proof, the existence of a gravitating, a calorific, an electrical, a magnetic, and a galvanic fluid, when it distinctly perceives their effects in a number of carefully conducted experiments; but does it follow from this, that speculative geology, in the absence of such perceived effects, may lay hold of these principles which are still hypothetical, and make use of them as if they were agents perfectly known, and entirely subjected to its power? And if geologists have the candour to own that they know nothing whatever of the part which the different etherial or atmospherical fluids may have acted in the primitive formation of the earth, is not this the same as owning the absolute impossibility of their being able to form a primitive history of the globe? The theory of chemical affinities, or of atomic attractions, has furnished us with some just ideas concerning the primitive formation of solid detached bodies; but as long as the law according to which these attractions decrease, remains unknown, and whilst we neither know the agents nor the processes which nature employs in the greater number of cases, the chemist can impart to us no positive and precise information as to one single operation of the unknown power which has produced, or which sustains, the universe. Still less can be trace the immense chain of its operations, the last link of which is attached. to the throne of the Almighty. with celes The strongest argument against the possibility of a theo- Connection ry of the earth, appears to be suggested by a consideration of geology of that admirable system of celestial mechanics whose un- tial mechaalterable laws maintain the globes in their respective posi nics. |