THAT great changes, of a kind and intensity quite different from the common course of events, and which may therefore properly be called catastrophes , have taken place upon the earth's surface, was an opinion which appeared to be forced upon men by obvious facts. Rejecting, as a mere play of fancy, the notions of the destruction of the earth by cataclysms or conflagrations, of which we have already spoken, we find that the first really scientific examination of the materials of the earth, that of the Sub-Apennine hills, led men to draw this inference. Leonardo da Vinci, whom we have already noticed for his early and strenuous assertion of the real marine origin of fossil impressions of shells, also maintained that the bottom of the sea had become the top of the mountain; yet his mode of explaining this may perhaps be claimed by the modern advocates of uniform causes, as more allied to their opinion, than to the doctrine of catastrophes . But  Steno, in 1669, approached nearer to this doctrine: for he asserted that Tuscany must have changed its face at intervals, so as to acquire six different configurations, by the successive breaking down of the older strata into inclined positions, and the horizontal deposit of new ones upon them. Strabo, indeed, at an earlier period had recourse to earthquakes, to explain the occurrence of shells in mountains; and Hooke published the same opinion later. But the Italian geologists prosecuted their researches under the advantage of having, close at hand, large collections of conspicuous and consistent phenomena. Lazzaro Moro, in 1740, attempted to apply the theory of earthquakes to the Italian strata, but both he and his expositor, Cirillo Generelli, inclined rather to reduce the violence of these operations within the ordinary course of nature, and thus leant to the doctrine of uniformity, of which we have afterwards to speak. Moro was encouraged in this line of speculation by the extraordinary occurrence, as it was deemed by most persons, of the rise of a new volcanic island from a deep part of the Mediterranean, near Santorino, in 1707. But in other countries, as the geological facts were studied, the doctrine of catastrophes appeared to gain ground. Thus in England, where, through a large part of the country, the coal-measures are extremely inclined and contorted, and covered over by more horizontal fragmentary beds, the opinion that  some violent catastrophe had occurred to dislocate them, before the superincumbent strata were deposited, was strongly held. It was conceived that a period of violent and destructive action must have succeeded to one of repose; and that, for a time, some unusual and paroxysmal forces must have been employed in elevating and breaking the preexisting strata, and wearing their fragments into smooth pebbles, before nature subsided into a new age of tranquillity and vitality. In like manner Cuvier, from the alternations of fresh-water and saltwater species in the strata of Paris, collected the opinion of a series of great revolutions, in which " the thread of induction was broken." Delue and others, to whom we owe the first steps in geological dynamics, attempted carefully to distinguish between causes now in action, and those which have ceased to act; in which latter class they reckoned the causes which have elevated the existing continents. This distinction was assented to by many succeeding geologists. The forces which have raised into the clouds the vast chains of the Pyrenees, the Alps, the Andes, must have been, it was deemed, something very different from any agencies now operating.
This opinion was further confirmed by the appearance of a complete change in the forms of animal and vegetable life, in passing from one formation to another. The species of which the remains occurred, were entirely different, it was said, in two successive epochs: a new creation appears  to have intervened; and it was readily believed that a transition, so entirely out of the common course of the world, might be accompanied by paroxysms of mechanical energy. Such views prevail extensively among geologists up to the present time: for instance, in the comprehensive theoretical generalisations of Elie de Beaumont and others, respecting mountain- chains, it is supposed that, at certain vast intervals, systems of mountains, which may be recognised by the parallelism of course of their inclined beds, have been disturbed and elevated, lifting up with them the aqueous strata which had been deposited among them in the intervening periods of tranquillity, and which are recognised and identified by means of their organic remains: and according to the adherents of' this hypothesis, these sudden elevations of mountain- chains have been followed, again and again, by mighty waves, desolating whole regions of the earth.
The peculiar bearing of such opinions upon the progress of physical geology will be better understood by attending to the doctrine of uniformity, which is opposed to them, and with the consideration of which we shall close our survey of this science, the last branch of our present task.
The opinion that the history of the earth had involved a series of catastrophes, confirmed by the two great classes of facts, the symptoms of mechanical  violence on a very large scale, and of complete changes in the living things by which the earth had been tenanted, took strong hold or the geologists of England, France, and Germany. Hutton, though he denied that there was evidence of a beginning of the present state of things, and referred many processes in the formation of strata to existing causes, did not assert that the elevatory forces which raise continents from the bottom of the ocean, were of the same order, as well as of the same kind, with the volcanoes and earthquakes which now shake the surface. His doctrine of uniformity was founded rather on the supposed analogy of other lines of speculation, than on the examination of the amount of changes now going on. " The Author of nature," it was said, " has not permitted in His works any symptom of infancy or of old age, or any sign by which we may estimate either their future or their past duration :" and the example of the planetary system v as referred to in illustration of this. And the persuasion that the champions of this theory were not disposed to accept the usual opinions on the subject of creation, was allowed, perhaps very unjustly, to weigh strongly against them in the public opinion.
While the rest of Europe had a decided bias towards the doctrine of geological catastrophes, the phenomena of Italy, which, as we have seen, had already tended to soften the rigour of that doctrine, in the progress of speculation from Steno to Generelli,, were destined to mitigate it still more, by converting  to the belief of uniformity transalpine geologists who had been bred up in the catastrophist creed. This effect was, indeed, gradual. For a time the distinction of the recent and the tertiary period was held to be marked and strong. Brocchi asserted that a large portion of the Sub-Apennine fossil shells belonged to living species of the Mediterranean Sea: but the geologists of the rest of Europe turned an incredulous ear to this Italian tenet; and the persuasion of the distinction of the tertiary and the recent period was deeply impressed on most geologists by the memorable labours of Cuvier and Brongniart on the Paris basin. Still, as other tertiary deposits were examined, it was found that they could by no means be considered as contemporaneous, but that they formed a chain of posts, advancing nearer and nearer to the recent period. Above the strata of the basins of London and Paris, lie the newer strata of Touraine, of Bourdeaux, of the valley of the Bormida and the Superga near Turin, and of the basin of Vienna, explored by AI. Constant Prevost. Newer and higher still than these, are found the Sub- Apennine formations of Northern Italy, and probably of the seine period, the English " crag" of Norfolk and Suffolk. And most of these marine formations are associated with volcanic products and fresh-water deposits, so as to imply apparently a font, train of alternations of corresponding processes. It may easily be supposed that, when the subject had assumed this  form, the boundary of the present and past condition of the earth was in some measure obscured. But it was not long before a very able attempt was made to obliterate it altogether. In 1828, Mr. Lyell set out on a geological tour through France and Italy. He had already conceived the idea of classing the tertiary groups by reference to the number of recent species which were found in a fossil state. But as he passed from the north to the south of Italy, he found, by communication with the best fossil conchologists, Borelli at Turin, Guidotti at Parma, Costa| at Naples, that the number of extinct species decreased; so that the last-mentioned naturalist, from an examination of the fossil shells of Otranto and Calabria, and of the neighbouring seas, was oft opinion that few of the tertiary shells were of extinct species. To complete the series of proof, Mr. Lyell himself explored the strata of Ischia, and found, 2000 feet above the level of the sea, shells, which were all pronounced to be of species now inhabiting the Mediterranean; and soon after, he made collections of a similar description on the flanks of Etna, in the Val di Noto, and in other places.
The impression produced by these researches is described by himelf. "In the course of my tour I had been frequently led to reflect on the precept of Descartes, that a philosopher should once in his life doubt every thing he had been taught; but I still retained so much faith in my early geological creed as to feel the most lively surprise on visiting Sortino, Pentalica, Syracuse, and other parts of the  Val di Noto, at beholding a limestone of enormous thickness, filled with recent shells, or sometimes with mere casts of shells, resting, on marl in which shells of Mediterranean species were imbedded in a high state of preservation. All idea of attaching a high antiquity to a regularly-stratified limestone, in which the casts and impressions of shells alone were visible, vanished at once from my mind. At the same time, I was struck with the identity of the associated igneous rocks of the Val di Noto with well-known varieties of ' trap' in Scotland and other parts of Europe; varieties which I had also seen entering largely into the structure of Etna.
"I occasionally amused myself," Mr. Lyell adds, "with speculating on the different rate of progress which geology might have made, had it been first cultivated with success at Catania, where the phenomena above alluded to, and the great elevation of the modern tertiary beds in the Val di Noto, and the changes produced in the historical era by the Calabrian earthquakes, would have been familiarly known."
Before Mr. Lyell entered upon his journey, he had put in the hands of the printer the first volume of his " Principles of Geology, being an attempt to explain the former Changes of the Earth's Surface by reference to Causes now in Operation." And after viewing such phenomena as we have spoken of, he, no doubt, judged that the doctrine of catastrophes of a kind entirely different from the existing course of events, would never have been generally received,  if geologists had formed their opinions upon the Sicilian strata. The boundary separating the present from the anterior state of things crumbled away; the difference of fossil and recent species had disappeared, and, at the same time, the changes of position which marine strata had undergone, although not inferior to those of earlier geological periods, might be ascribed, it was thought, to the same kind of earthquakes as those which still agitate that region. Both the supposed proofs of catastrophic transition. the organical and the mechanical changes, failed at the same time; the one by the removal of the fact, the other by the exhibition of the cause. The powers of earthquakes, even such as they now exist, were, it was supposed, if allowed to operate for an illimitable time, adequate to produce all the mechanical effects which the strata of all ages display. And it was declared that all evidence of a beginning of the present state of the earth, or of any material alteration in the energy of the forces by which it has been modified at various epochs, was entirely wanting.
Other circumstances in the progress of geology tended the same way. Thus, in cases where there had appeared in one country a sudden and violent transition from one stratum to the next, it was found, that by tracing the formations into other countries, the chasm between them was filled up by intermediate strata; so that the passage became as gradual and gentle as any other step in the series. For example, though the conglomerates, which in  some parts of England overlie the coal-measures, appear to have been produced by a complete diseontinuity in the series of changes; yet in the coal- fields of Yorkshire, Durham, and Cumberland, the transition is smoothed down in such a way that the two formations pass into each other. A similar passage is observed in Central Germany, and in Thuringia is so complete, that the coal-measures have sometimes been considered as subordinate to the todtliegendes.
Upon such evidence and such arguments, the doctrine of catastrophes was rejected with some contempt and ridicule; and it was maintained, that the operation of the causes of geological change may properly and philosophically be held to have been uniform through all ages and periods. On this opinion, and the grounds on which it has been urged, we shall make a few concluding remarks.
It must be granted at once, to the advocates of this geological uniformity, that we are not arbitrarily to assume the existence of catastrophes. The degree of uniformity and continuity with which terremotive forces have acted, must be collected, not from any gratuitous hypothesis, but from the facts of the case. We must suppose the causes which have produced geological phenomena, to have been as similar to existing causes, and as dissimilar, as the effects teach us. We are to avoid all bias in favour of power) deviating in kind and degree from those which act at present; a bias, which Mr. Lyell asserts, has extensively prevailed among geologists. 
But when Mr. Lyell goes further, and considers it a merit in a course of geological speculation that it rejects any difference between the intensity of existing and of past causes, we conceive that he errs no less than those whom he censures. "An earnest and patient endeavour to reconcile the former indications of change," with any restricted class of causes,-- a habit which he enjoins,--is not, we may suggest, the temper in which science ought to be pursued. The effects must themselves teach us the nature and intensity of the causes which have operated; and we are in danger of error, if we seek for slow and shun violent agencies further than the facts naturally direct us, no less than if we were parsimonious of time and prodigal of violence. Time, inexhaustible and ever accumulating his efficacy, can undoubtedly do much for the theorist in geology; but Force, whose limits we cannot measure, and whose nature we cannot fathom, is also a power never to be slighted: and to call in the one to protect us from the other, is equally presumptuous, to whichever of the two our superstition leans. To invoke Time, with ten thousand earthquakes, to overturn and set on edge a mountain-chain, should the phenomena indicate the change to have been sudden and not successive, would be ill excused by pleading the obligation of first appealing to known causes.
In truth, we know causes only by their effects; and in order to learn the nature of the causes which modify the earth, we must study them through all ages of their action, and not select arbitrarily the  period in which we live as the standard for all other epochs. The forces which have produced the Alps and the Andes are known to us by experience, no less than the forces which have raised Etna to its present height; for we learn their amount in both cases by their results. Why, then, do we make a merit of using the latter case as a measure for the former? Or how can we know the true scale of such force, except by comprehending in our view all the facts which we can bring together ?
In reality, when we speak of the uniformity of nature, are we not obliged to use the term in a very large sense, in order to make the doctrine at all tenable? It includes catastrophes and convulsions of a very extensive and intense kind; what is the limit to the violence which we must allow to these changes ? In order to enable ourselves to represent geological causes as operating with uniform energy through all time, we must measure our time by long cycles, in which repose and violence alternate; how long may we extend this cycle of change, the repetition of which we express by the word uniformity?
And why must we suppose that all our experience, geological as well as historical, includes more than one such cycle ? Why must we insist upon it, that man has been long enough an observer to obtain the average of forces which are changing through immeasurable time?
The analogy of other sciences has been referred to, as sanctioning this attempt to refer the whole train of facts to known causes. To have done this, it has  been said, is the glory of astronomy: she seeks no hidden virtues, but explains all by the force of gravitation, which we witness operating at every moment. But let us ask, whether it would really have been a merit in the founders of physical astronomy, to assume that the celestial revolutions resulted front any selected class of known causes ? When Newton first attempted to explain the motions of the moon by the force of gravity, and failed because the measures to which he referred were erroneous, would it have been philosophical in him, to insist that the difference which he found ought to be overlooked; since otherwise we should be compelled to go to causes other than those which we usually witness in action ? Or was there any praise due to those who assumed the celestial forces to be the same with gravity, rather than to those who assimilated them with any other known force, as magnetism, till the calculation of the laws and amount of these forces, from the celestial phenomena, had clearly sanctioned such an identification ? We are not to select a conclusion now well proved, to persuade ourselves that it would have been wise to assume it anterior to proof, and to attempt to philosophize in the method thus recommended.
Again, the analogy of astronomy has been referred to, as confirming the assumption of perpetual uniformity. The analysis of the heavenly motions, it has been said, supplies no trace of a beginning, no promise of an end. But here, also, this analog' is erroneously applied. Astronomy, as the science  of cyclical motions, has nothing in common with geology. But look at astronomy when she has an analogy with geology; consider our knowledge of the heavens as a palaetiolgoical science;--as the study of a past condition, from which the present is derived by causes acting in time. Is there then no evidence of a beginning, or of a progress ? What is the import of the nebular hypothesis ? A luminous matter is condensing, solid bodies are forming, are arranging themselves into systems of cyclical motion; in short, we have exactly what we are told, on this analogy, we ought not to have;--the beginning of a world. To justify this argument, I will not maintain the truth of the nebular hypothesis; but if geologists wish to borrow maxims of philosophizing. from astronomy, such speculations as have led to that hypothesis must be their model.
Or, let them look at any of the other provinces of palaaetiological speculation; at the history of states, of civilization, of languages. We may assume some resemblance or connexion between the principles which determined the progress of government, or of society, or of literature, in the earliest ages, and those which now operate, but who has speculated successfully, assuming an identity of such causes ? Where do we now find a language in the process of formation, unfolding itself in inflexions, terminations, changes of vowels by grammatical relations, such as characterize the oldest known languages? Where do we see a nation, by its natural faculties, inventing writing, or the arts of life, as we find them  in the most ancient civilized nations ? We may assume hypothetically, that man's faculties develop themselves in these ways; but we see no such effects produced by these faculties, in our own time, and now in progress, without the influence of foreigners.
Is it not clear, in all these cases, that history does not exhibit a series of cycles, the aggregate of which may be represented as a uniform state, without indication of origin or termination? Does it not rather seem evident that, in reality, the whole course of the world, from the earliest to the present times, is but one cycle, yet unfinished;--offering, indeed, no clear evidence of the mode of its beginning; but still less entitling us to consider it as a repetition or series of repetitions of what had gone before ?
Thus we find, in the analogy of the sciences, no confirmation of the doctrine of uniformity, as it has been maintained in geology. Yet we discern, in this analogy, no ground for resigning our hope, that future researches, both in geology and in other palaetiological sciences, may throw much additional light on the question of the uniform or catastrophic progress of things, and on the earliest history of the earth and of man. But when we see how wide and complex is the range of speculation to which our analogy has referred us, we may well be disposed to pause in our review of science;--to survey from our present position the ground that we have passed over;--and thus to collect, so far as we may, guidance and encouragement to enable us to advance in the track which lies before us. 
Before we quit the subject now under consideration, we may, however, observe that what the analogy of science really teaches us, as the most promising means of promoting this science, is tile strenuous cultivation of the two subordinate sciences, geological knowledge of facts, and geological dynamics. These are the two provinces of knowledge-corresponding to phenomenal astronomy, and mathematical mechanics --which may lead on to the epoch of the Newton of geology. We may, indeed, readily believe that we have much to do in both these departments. While so large a portion of the globe is geologically unexplored; while all the general views which are to extend our classifications satisfactorily from one hemisphere to another, from one zone to another, are still unformed; while the organic fossils of the tropics arc almost unknown, and their general relation to the existing state of things has not even been conjectured; --how can we expect to speculate rightly and securely, respecting the history of the whole of our globe? And if geological classification and description are thus imperfect, the knowledge of geological causes is still more so. As we have seen, the necessity and the method of constructing a science of such causes, are only just beginning to be perceived. Here, then, is the point where the labours of' geologists may be usefully applied; and not in premature attempts to decide the widest and abstrusest questions, which the human mind can propose to itself.
It has been stated, that when the Geological Society of London was formed, their professed  object was to multiply and record observations, and patiently to await the result at some future time; and their favourite maxim was, it is added, that the time was not yet come for a general system of geology. This was a wise and philosophical temper, and a due appreciation of their position. And even now, their task is not yet finished; their mission i' not yet accomplished. They have still much to do? in the way of collecting facts; and in entering upon the exact estimation of causes, they have only just thrown open the door of a vast labyrinth, which it may employ many generations to traverse, but which they must needs explore, before the!- c an penetrate to the oracular chamber of Truth.
I REJOICE, on many accounts, to find myself arriving at the termination of the task which I have attempted. One reason wily I am glad to close my history is, that in it I have been compelled, especially in the latter part of my labour-q, to speak as a judge respecting eminent philosophers whom I reverence as my teachers in those very sciences on which I have had to pronounce;--if, indeed, even the appellation of pupil be not too presumptuous. But I doubt not that such men are as full of candour and tolerance, as they arc of knowledge and thought. And if they deem, as I did, that such a history of science ought to be attempted, they will know that it was not only the historian's privilege, but his duty, to estimate the import and amount of  the advances which he had to narrate; and if they judge, as I trust they will, that the attempt has been made with full integrity of intention and no want of labour, they will look upon the inevitable imperfections of the execution of my work with indulgence and hope.
There is another source of satisfaction in arriving at this point of my labours. If, after our long wandering through the region of physical science, we were left with minds unsatisfied and unraised, to ask, "Whether this be all?"--our employment might well be deemed weary and idle. If it appeared that all the vast labour and intense thought which has passed under our review had produced nothing but a barren knowledge of the external world, or a few arts ministering merely to our gratification; or if it seemed that the methods of arriving at truth, so successfully applied in these cases, aid us not when we come to the higher aims and prospects of our being;--this history might well be estimated as no less melancholy and unprofitable than those which narrate the wars of states and the wiles of statesmen. But such, I trust, is not the impression which our survey has tended to produce. At various points, the researches which we have followed out, have offered to lead us from matter to mind,, from the external to the internal world; and it was not because the thread of investigation snapped in our hands, but rather because we were resolved to confine ourselves, for the present, to the material sciences, that we did not proceed onwards to subjects  of a closer interest. I trust, also, that it will appear, that the most perfect method of obtaining speculative truth,--that of which I have had to relate the result,--is by no means confined to the least worthy subjects; but that the methods of learning what is really true, though they must assume different aspects in cases where a mere contemplation of external objects is concerned, and where our own internal world of thought, feeling, and will, supplies the matter of our speculations, have yet a unity and harmony throughout all the possible employments of our minds. To be able to trace such connexion-q as this, is the proper sequel, and would be the high reward, of the labour which has been bestowed on the present work. And if a persuasion of the reality of such connexion-q, and a preparation for studying them, have been conveyed to the reader's mind while he has been accompanying me through our long survey, his time may not have been employed on these pages in vain. However vague and hesitating and obscure may be such a persuasion, it belongs, I doubt not, to the dawning of a better philosophy, which it may be my lot, perhaps, to develop more fully hereafter, if permitted by that Superior Power to whom all sound philosophy directs our thoughts.
 " Here is a part of the earth which has become more light, and which rises, while the opposite part approaches nearer to the centre, and what was the bottom of the sea is become the top of the mountain."--Venturi's Léonard da Vinci.
 Lyell, i. 3. p. 64.
 Lyell, i. 4, p 94
 Lyell, 1st ed., vol. iii. p. 61.
 1st ed. vol. iii. Pref.
 Lyell, 1st ed.. Pref. x.
 De la Beche, p. 414, Manual.
 Lyell, B. iv. c. i. p. 328.
 Lyell, B. i. c. iv.. p. 103.