John Playfair

“ It is only the philosopher, who has deeply meditated on the effects which action long continued is able to produce, and on the simplicity of the means which nature employs in all her operations, who sees in this nothing but the gradual working of a stream, that once flowed over the top of the ridge which it now so deeply intersects, and has cut its course through the rock, in the same way, and almost with the same instrument, by which the lapidary divides a block of marble or granite. ”

“ Among the prejudices which a new theory of the earth has to overcome, is an opinion, held, or affected to be held, by many, that geological science is not yet ripe for such elevated and difficult speculations. They would, therefore, get rid of these speculations, by moving the previous question, and declaring that at present we ought to have no theory at all. We are not yet, they allege, sufficiently acquainted with the phenomena of geology; the subject is so various and extensive that our knowledge of it must for a long time, perhaps for ever, remain extremely imperfect. ”

“ When we are assured of the existence of such a power as this in the mineral regions, we should argue with singular inconsistency, if we did not ascribe to it all the other appearances of motion in those regions, which it is adequate to produce. If nature in her subterraneous abodes is provided with a force that could burst asunder the massy pavement of the globe, and place the fragments upright upon their edges, could she not, by the same effort, raise them from the greatest depths of the sea, to the highest elevation of the land? ”

“ In a word, it is the peculiar excellence of this theory, that it ascribes to the phenomena of geology an order similar to that which exists in the provinces of nature with which we are best acquainted; that it produces seas and continents, not by accident, but by the operation of regular and uniform causes; that it makes the decay of one part subservient to the restoration of another, and gives stability to the whole, not by perpetuating individuals, but by reproducing them in succession. ”

“ It is true, that it is not by the solar rays that subterraneous heat is produced; but still, from this instance, we see, that there is no incongruity in supposing the production of heat to be independent of combustible bodies, and of vital air. We are indeed, in all cases, strangers to the origin of heat; philosophers dispute, at this moment, concerning the source of that which is produced by burning; and much more are they at a loss to determine, what upholds the light and heat of the great luminary, which animates all nature by its influence. ”

“ When it is considered, that over all the vast and uneven surface, which reaches from the Alps to the Euxine, and from the mountains of Crapack to those of Hæmus, a regular communication is kept up between every point and the line of greatest depression, in which the river flows, no one can hesitate to acknowledge, that it is the agency of the waters alone which has opened them a free passage through all the intricacies of this amazing labyrinth. ”

“ Granite, it has been just said, exists most commonly in masses; and these masses are rarely, if ever, incumbent on any other rock: they are the basis on which others rest, and seem, for the most part, to rise up from under the ancient, or primary strata. The granite, therefore, wherever it is found, is inferior to every other rock; and as it also composes many of the greatest mountains, it has the peculiarity of being elevated the highest into the atmosphere, and sunk the deepest under the surface, of all the mineral substances with which we are acquainted. ”

“ Thus, with Dr Hutton, we shall be disposed to consider those great chains of mountains, which traverse the surface of the globe, as cut out of masses vastly greater, and more lofty than any thing that now remains. ”

“ May not great, dense, and fixed bodies, when heated beyond a certain degree, emit light so copiously, as, by the emission and reaction of its light, and the reflections and refractions of its rays within its pores, to grow still hotter, till it comes to a certain period of heat, such as is that of the sun? And, are not the sun and fixed stars great earths, vehemently hot, whose heat is conserved by the greatness of the bodies, and the mutual action and reaction between them and the light which they emit? ”

“ In what relates to the future, the two systems are not more like than in what relates to the past Buffon represents the cooling of our planet, and its loss of heat, as a process continually advancing, and which has no limit, but the final extinction of life and motion over all the surface, and through all the interior, of the earth. The death of nature herself is the distant but gloomy object that terminates our view, and reminds us of the wild fictions of the Scandinavian mythology, according to which, annihilation is at last to extend its empire even to the gods. ”

“ The spars and veinstones which are thrown out in the rubbish of our mines, may be as precious in the eyes of nature, as conducive to the great objects of her economy, and are certainly as characteristic of mineral veins, as the ores of silver or gold, to which we attach so great a value. ”

“ It would, therefore, be extremely unphilosophical to suppose, that any other cause has changed the relative level of the strata, and the surface of the sea, than that which has, in so many cases, raised the strata from a horizontal to a highly inclined, or even vertical situation: it would be to introduce the action of more causes than the phenomena require, and to forget, that nature, whose operations we are endeavouring to trace, combines the possession of infinite resources with the most economical application of them. ”

“ But the philosopher who has ascended to his theory by a regular generalization of facts, and who descends from it again by drawing such palpable conclusions as may be compared with experience, furnishes the infallible means of distinguishing between perfect science and ingenious fiction. ”

“ Such, according to Dr Hutton's theory, are the changes which the daily operations of waste have produced on the surface of the globe. These operations, inconsiderable if taken separately, become great, by conspiring all to the same end, never counteracting one another, but proceeding, through a period of indefinite extent, continually in the same direction. Thus every thing descends, nothing returns upward; the hard and solid bodies every where dissolve, and the loose and soft no where consolidate. ”

“ If we proceed in our survey from the shores, inland, we meet at every step with the fullest evidence of the same truths, and particularly in the nature and economy of rivers. Every river appears to consist of a main trunk, fed from a variety of branches, each running in a valley proportioned to its size, and all of them together forming a system of vallies, communicating with one another, and having such a nice adjustment of their declivities, that none of them join the principal valley, either on too high or too low a level ”

“ That a hypothesis, formed in such direct opposition to the most obvious principles of inductive reasoning, should have been imagined by a philosopher who had examined the phenomena of Etna and Vesuvius with much attention, and described them with great accuracy and truth, is more wonderful than that it should have been adopted by mineralogists, whose views of nature may have been confined within a cabinet or a laboratory. ”

“ The variety of geological appearances which a traveller meets with, is not at all in proportion to the extent of country he traverses; and if he take in a portion of land sufficient to include primitive and secondary strata, together with mountains, rivers, and plains, and unstratified bodies in veins and in masses, though it be not a very large part of the earth's surface, he may find examples of all the most important facts in the history of fossils. ”

“ It should never be forgotten, that a theory which accounts for any thing, and a theory which accounts for nothing, stand precisely on the same footing, and ought to be banished from all parts of philosophy, as they have been from those sciences which are justly honoured with the name of accurate. ”

“ But if it is once settled, that a theory of the earth ought to have no other aim but to discover the laws that regulate the changes on the surface, or in the interior of the globe, the subject is brought within the sphere either of observation or analogy; and there is no reason to suppose, that man, who has numbered the stars, and measured their forces, shall ultimately prove unequal to this investigation. ”

“ In all this, however, we are guided much more by fancy than reason; for, in order to depress or elevate the absolute level of the sea, by a given quantity, in any one place, we must depress or elevate it by the same quantity over the whole surface of the earth; whereas no such necessity exists with respect to the elevation or depression of the land. To make the sea subside 30 feet all round the coast of Great Britain, it is necessary to displace a body of water 30 feet deep over the whole surface of the ocean. ”

“ A theory is never more unfairly dealt with, than when those parts are separated which were meant to support one another, and each left to stand or fall by itself. This, however, is precisely what is done in the present instance; for Dr Hutton's theory of granite would not deserve a moment's consideration, if it were so inartificially constructed, as to suppose that granite was originally fluid, and yet to point out no means of hindering this fluid from diffusing itself over the strata, and settling in a horizontal plane. ”

“ On such shores, the fragments of rock once detached, become instruments of further destruction, and make a part of the powerful artillery with which the ocean assails the bulwarks of the land: they are impelled against the rocks, from which they break off other fragments, and the whole are thus ground against one another; whatever be their hardness, they are reduced to gravel, the smooth surface and round figure of which, are the most certain proofs of a detritus which nothing can resist. ”

“ If indeed this theory of the earth is as well founded as we suppose it to be, the lapse of time must necessarily remove all objections to it, and the progress of science will only develope its evidence more fully. ”

“ As this philosopher never embarrasses himself about preserving a uniformity in the course of nature, he will tell us, that though it may be true, that neither the air, the upper part of the earth's surface, nor even the sea, contain at present any thing like the materials of the veins, yet the time was when these materials were all mingled together in the chaotic mass, and constituted one vast fluid, encompassing the earth; from which fluid it was, that the minerals were precipitated and deposited in the clefts and fissures of the strata. ”

“ If the theory of unstratified mountains, namely those of whinstone, porphyry, and granite, be admitted as laid down above, it will furnish a measure of the destruction which has taken place in the stratified rocks, and of the vast depredations which have been made upon them since they were raised up from the bottom of the sea. Like every other measure, however, of wasting, by a thing that is itself subject to waste, it can only give a minimum, or a limit which the quantity wasted must necessarily exceed. ”

“ If we begin with examining the coasts of our own island, we shall find clear evidence every where, that the sea once reached higher up upon the land than it does at present. The marks of an ancient sea beach are to be seen beyond the present limits of the tide, and beds of sea shells, not mineralized, are found in the loose earth or soil, sometimes as high as thirty feet above the present level of the sea. ”

“ The smooth surface of the rocks in all waterfalls, their rounded surface, and curious excavations, are the most satisfactory proofs of the constant attrition which they endure; and, where the rocks are deeply intersected, these marks often reach to a great height above the level on which the water now flows. The phenomena, in such instances, are among the arguments best calculated to remove all incredulity respecting the waste which rivers have produced, and are continuing to produce. They suffer no doubt to remain, that the height and asperity of every waterfall are continually diminishing ”

“ That the earth is a spheroidal body, compressed at the poles, or elevated at the equator, is a fact established by many accurate experiments; and though these experiments do not exactly coincide, as to the degree of oblateness which they give to that spheroid, they agree sufficiently to put it beyond all dispute, that the earth, though solid, has nearly the same figure which it would assume if fluid, in consequence of its rotation on its axis. ”

“ No force of water could raise a stone like the pierre de goutté from the bottom of a - 408 - valley, to the top of a steep hail. Indeed, if we suppose a great fragment of rock to be hurried along on a horizontal or an inclined plane, by the force of water, the moment it comes to a deep valley, and has to rise up over an ascent of a certain steepness, it will remain at rest; the water itself will lose its velocity, and the heavy bodies which it carried with it will proceed no farther. ”

“ The mechanical forces employed in the disintegration of mineral substances, are more easily marked than the chemical. Here again water appears as the most active enemy of hard and solid bodies; and, in every state, from transparent vapour to solid ice, from the smallest rill to the greatest river, it attacks whatever has emerged above the level of the sea, and labours incessantly to restore it to the deep. ”

“ To trace the series of these revolutions, to explain their causes, and thus to connect together all the indications of change that are found in the mineral kingdom, is the proper object of a Theory of the Earth. ”

“ If, however, we ascribe to the mountains a magnitude and elevation vastly greater than that which they now possess; if we regard the valleys between them as cut out by the rivers and torrents from an immense rampart of solid rock, neither materials sufficiently great, nor agents sufficiently powerful, will appear to be wanting, for collecting bodies of gravel and other loose materials, equal to any that are found on the surface of the earth. ”

“ The Huttonian Theory is, indeed, the only one which possesses the means of reconciling the elevation of the strata with their horizontal deposition, and which is entitled to consider stratification, in whatever plane it may be, as originally the work of the ocean. The geologists who attach themselves exclusively to the action of water, will never be able to extend the dominion of that element so far as Dr Hutton has done, by combining it with fire. ”

“ Thus theory and observation mutually assist one another; and the spirit of system, against which there are so many and such just complaints, appears, nevertheless, as the animating principle of inductive investigation. The business of sound philosophy is not to extinguish this spirit, but to restrain and direct its efforts. ”