duced disturbance. The igneous rocks were not that cause; for they have themselves been disturbed, together with the fossiliferous Lower Silurian rocks amid which they lie; and the mountainous character of the country, as it now presents itself, is due, not to direct volcanic action, but to the unequal hardness of igneous and aqueous masses, acted on by many denudations both ancient and modern, both marine and subaerial. These causes, aided by faults which often brought hard and soft rocks into immediate juxtaposition, have given rise to all the rugged outlines on the surface of Wales, the hard rocks more strongly resisting decay and waste, the soft ones yielding to time, the sea, and the weather, with greater ease; and thus it happens that the harder masses generally form headlands, and the summits of the mountains, though often found elsewhere; while the softer strata, wasted away by the sea and by rain and rivers, are apt to lie in the recesses of bays and in valleys and plains. This kind of argument I could equally well apply to the Carboniferous formations of Scotland, where igneous rocks are rife, and, indeed, to all those areas where igneous masses of ancient date are found intermixed with sedimentary strata*.

Again, if we go to the Alps, and look at the strata there, which are disturbed on the greatest scale; in all that part of the range that I best know, from east to west for more than 100 miles in length, I have never seen a fragment of what I can call a true igneous rock. Gneiss there is, and granite there is, which, according to old ideas-a great advance in their day-some have been apt to classify either as common igneous productions or as closely allied to them; but no basalts or greenstones, or rocks allied to these, play any important part in the structure of the country, although the strata have been disturbed in a manner of which no conception can be formed by those who have only studied such minor mountains as those of the British Isles. There, in the Alps, we find areas as large as half an English county, in which a whole series of formations has been turned upside down. But by what means were masses of strata many thousands of feet thick bent and contorted and raised into the air so as to produce existing results by affording matter for the elements to work upon ? Not by igneous or other pressure and upheaval from below, for that would stretch instead of crumpling the strata in the manner we find them in great mountain-chains like the Alps, or in less disturbed groups like those of the Highlands, Wales, and Cumberland, which are only fragments of older mountain-ranges; but, perhaps, as some have supposed, because of the radiation from the earth of heat into space, producing gradually a marked shrinkage of the earth's hardened crust, which, giving way, became crumpled along lines more or less irregular, thus producing partial upheavals, though the bulk of the whole globe was diminishing. A modification of this hypothesis does not attempt to explain the positive cause of the shrinkage, but simply states, that from some unknown cause, irrespective of radiation, great areas of the earth's crust having been depressed, broad lines that lie between them have been contorted and heaved into the air in the manner already indicated. Such shrinkage and crumpling, however it was produced, when most intense and on the greatest scale, is always (where I know it) accompanied by the appearance of gneissic or other metamorphic rocks, and of granite or its allies; and it has often been the custom to attribute the disturbance of the strata in such mountain-ranges and their metamorphism into gneiss, crystalline marble, and the like, to the intrusion of granite." But my opinion has long been that, with regard to gneiss and granite, the first has been produced by processes of metamorphism which had no necessary connexion with the intrusion of granite, while granite itself is often simply the result of extreme metamorphism, having passed through and beyond the stage of imperfect crystallization, characteristic of gneiss, into that state of more perfect crystallization which marks well-developed granite. If this be so, then, so far from the intrusion of granite having produced such mountains as those I speak of, both gneiss and granite would rather seem to be results of the forces that formed the mountainchains, I cannot tell how, but possibly connected with the heat produced by the intense contortion of such vast masses of strata, the parts of which now exposed by denudation were then deep underground. There is, however, a difficulty here

This argument has of course no immediate application to existing or late Tertiary volcanic areas, such as those of Auvergne, where entire and ruined craters still exist.

perhaps insuperable, and which my knowledge does not enable me to grapple with; viz., that if the shrinkage that contorted the strata were slow, the heat resulting from it might never have attained sufficient intensity to have produced, with the aid of alkaline waters, those common metamorphic masses, known as gneiss, granite, syenite, &c., and others less commonly recognized as metamorphic, such as some of the quartz porphyries, for the heat thus generated may have escaped as fast as it was formed. But I cannot now enter on these details.

It has often been customary to speak of the Cumbrian mountains as a great dome, forces from below having heaved up the strata towards a central point, from whence the main valleys radiate as great rents produced by that upheaval. But the strata of Cumberland are not dome-shaped in the true geological sense. If it were so, the strata ought to dip from the centre. But instead of that we find Lower and Upper Silurian strata from the equivalents of the Llandeilo flags to the Ludlow beds, which though contorted, yet form an ascending series all across Cumberland from Cockermouth to Ambleside, with an average south-easterly dip. There is, indeed, nothing cone-like in the manner of their arrangement, and the igneous rocks associated with the Cumbrian strata have partaken of disturbances of the same ages as those that heaved up the Silurian rocks of Wales. Afterwards the whole series was planed across by marine denudation before the deposition of the Old Red Sandstone of the area; and then, but chiefly at later periods, the valleys were scooped out from a great tableland, an old plain of marine denudation, especially after the removal by denudation of the Carboniferous rocks which at one time probably cased and concealed the whole of the Silurian strata. In this manner the character of the mountains of the country was produced, the harder masses being apt to form the heights, craggy, yet often rounded by glacial action.

Now in disturbed districts, and in many not much disturbed, faults are more or less numerous, and they are of all ages and of varying amounts. On the Continent of Europe and in Britain, for example, from the Middle Tertiary strata downwards, somewhere or other, all the formations have been dislocated, some of the faults being of the amount of only a few inches or yards, and others of many thousands of feet. Several I know in Wales of 2000, 5000, or even 12,000 feet in amount; and as a rule it is found that the greatest faults intersect strata that have been most disturbed, while also it often happens (but not always) that the oldest strata have undergone most disturbance, because they have been more frequently affected by disturbing agents. On the north side of the Alps the Miocene rocks of the Rhigi are inverted and faulted against the older formations, and the amount of the throw must be very large, and as many Miocene species of mollusks are still living, far as it is removed from our epoch, this fault, by comparison with older ones, may almost be said to approach our own day.

Now the question arises whether the agencies that produced contortion of strata and faults, which in certain cases have resulted in the formation of great mountainchains, have been sudden in their operation, or if the changes have been as progressive and gradual as the operation of those agents of denudation-the sea in the formation of plains of marine denudation, old and new, and the outlines of coasts; together with the work of air, rain, rivers, frost, snow, and ice, that, long continued, have produced the familiar sculpturing of hill and valley. This is a very puzzling question to geologists, and various opinions have been stated. One of these is that we now live in a world, as it were, nearly in a finished state, and which will suffer no more catastrophes; another that the world now remains in a temporary state of repose after a succession of spasmodic throws which broke up suddenly great portions of the earth's crust, and repeatedly revolutionized the world, and that such efforts may recur at later periods a long way beyond our time; or again, that the state of tranquillity we now enjoy, in which change is constant, more or less slow, and very sure, has been the order for all time, as far as geologists can trace back the history of the world in the rocks that form its crust. These are the leading opinions on the subject, and my own inclines to the last.

But in the present state of our knowledge it is impossible to reduce to a demonstration the truth of this opinion. Those who fancy the world to be in a finished state are seemingly forgetful of the fact that the old rocks were made by the same operations as those that are now forming; and those who advocate sudden violence

and wide-spread revolution have, it seems to me, nothing beyond assertion to help them, founded on that kind of wonder and awe that arises from the contemplation of crags, peaks, and the inversions of the strata of great mountain-chains, or of other and kindred phenomena; while the advocates of peaceful change have little to say beyond an appeal to observed facts, gathered from a study of rocky masses and their contents, which to them seem to point throughout to gradual and continuous changes; and these imperfectly understood phenomena have induced a half intuitive and growing belief that the laws, both physical and biological, that govern the world are quiet, progressive, and unviolent.

Proceeding now a point further, the connexion of life with the modifications which have taken place in the crust of the earth somewhat helps us in our endeavours to understand the question. As every one knows, there have been great numbers of different genera and species inhabiting the world at different geological epochs, the remains of which lie buried in the various formations; and looked at on a large scale, and over broad areas, it is evident that there has been a succession of life, each of the greater series of formations being more or less marked by its own particular fauna. This fact led to the old geological doctrine that there had been many sudden creations, by which the world was at various times peopled; that these inhabitants, after long intervals, were as suddenly destroyed; that new creations came in, and that each formation was in this way marked by its peculiar forms of life. When, however, it was found that in some formations a few, or sometimes many, of the same species were common to two or more formations, this theory of complete and sudden extinction and creation was seen to be untenable. By and by, when the geological structure of Britain began to be minutely analyzed, it was found in cases of unconformable stratification, even when the upper formation was in time the next known member of the series to that which lay below, that breaks in the succession of marine life, partial or total, always accompanied such unconformities in stratification. It has, indeed, been a question with some geologists whether two marine faunas, commonly recognized as belonging to two distinct and far apart geological epochs, such as the Silurian and Carboniferous, could not have been contemporaneous in past eras, or indeed even now. It is very possible that something of this kind may have been the case; but in my opinion only in a mixed and minor way between periods or formations that in a geological sense were not far apart in time. When we consider the greater formations, such as Silurian and Carboniferous, Oolitic and Cretaceous, the probabilities, as I have elsewhere argued, are almost infinitely against this assumption; for if so, an Oolitic fauna, for example, in whole or in part might both underlie and overlie Cretaceous formations. But, however we may look upon this question, it is certain that the great principle of a succession of life, showing a method of change and progress, the old disappearing, and the new coming in, and breaks in succession of life, as I have shown in detail elsewhere, have a close connexion with unconformability of strata and gaps in geological time unrepresented by stratified formations over areas of varying size, such areas being determined by those agents that produced upheaval and denudation of continents and islands.

I could follow out this view with particulars, but without now doing so, this reasoning seems to assure us that there never has been universally over the world any complete destruction of life, but that the succession of being has gone on in regular order and sequence, though for a time, or for ever, we have lost many of the records-whole chapters, whole books, in consequence of the disturbances and slow denudations which the earth's crust has undergone. This must show, therefore, that there never has been any universal catastrophe which destroyed the life of the world; especially because many of the forms are still alive that belong to comparatively old epochs; and to my mind the continuity of genera and even of broader distinctions leads to a like result. But great changes in physical geography have often taken place in times too limited to have involved total changes of life; for life, I believe, dies out or changes not by violence or sudden edict, but by the slow effects of time. The north of Europe and America has been more than half submerged during the last glacial epoch, and re-arisen without the disappearance of any one marine mollusk. Of the fossils of the Crag, part of an old German ocean,

1866.

large percentages still remain; and the Miocene formation of the Alps, which contain many land plants barely distinguishable (if distinguishable) from living species, have been formed, upheaved, inverted, and faulted without a total destruction either of terrestrial or of aqueous life. Putting all these things together, I feel myself almost driven to the conclusion that all these changes have been so slow and gradual, that to occupants of old time, had there been human intelligence to observe, everything would have seemed to go on in the same slow, steady, and apparently undisturbed manner in which they appear to us to go on now; and if this be true, then, instead of having recourse to unusual catastrophic action to explain what is seen to have resulted, it all resolves itself into time-to effects in fact produced by small cumulative causes, which were more than equal to all the destructive forces attributed to eruptions of igneous rocks, the production of faults, and immense contortions of strata; and the effect of all, but not the final effect, has brought about the astonishing changes which the world has so visibly undergone, resulting in the present physical geology, physical geography, and life of the surface of the earth.

On Intermittent discharges of Petroleum and large deposits of Bitumen in the Valley of Pescara, Italy. By Prof. ANSTED, F.R.S.

On a Salse or Mud Volcano on the flanks of Etna, commencing to erupt in the month of January last. By Prof. ANSTED, F.R.S.

An Attempt to approximate the Date of the Flint Flakes of Devon and Cornwall. By C. SPENCE BATE, F.R.S.

On the Island of St. John in the Red Sea (the Ophiodes of Strabo).

By Dr. BEKE.

The author gives an account of his visit to the Island of St. John, in the Red Sea, which he described as an upraised coral-reef, with a sharp volcanic peak in the centre. It afforded neither water nor vegetable productions. There was evidence along both coasts of the Red Sea that the land was uprising. The author exhibited a number of geological specimens collected on the island.

On the occurrence of Flint Implements in the Gravel of the Little Ouse Valley at Thetford and elsewhere. By HENRY BRIGG, Jun.

The author in this paper described some discoveries of flint implements at five points in the valley of the Little Ouse, a river having a common origin with the Waverney at Lopham Ford, and which, after receiving the waters of the Thet and another small river, takes a north-west course, and joins the Great Ouse,

The country drained by the Little Ouse and its tributaries, is of the Upper Chalk, largely overlaid with glacial drift; and the river-valleys exhibit extensive deposits of the debris of these formations arranged terrace-like upon their sides.

From Thetford to Brandon the valley-gravels attain their greatest development, and are extensively quarried during the winter months for road-making material. It was at Santon, in the spring of 1862, that the first flint implement was discovered, and Mr. Brigg has since recorded further discoveries at the Red Hill and White Hill, Thetford (slight eminences upon the Abbey-heath, thus called by the pitmen from the colour of the gravels), Santon Downham, and further down the river, and without the valley, at Shrub Hill, in Feltwell fen.

The discoveries at the Red and White Hill are important; the first from the large number of implements that have been found, the latter from the occurrence in the same deposit of remains of the Elephas primigemus, Equus, Sus, &c. The implements of the Little-Ouse gravels are mostly of the spearhead form, with the usual variety of finish and staining. Many of them show traces of wear from use, while others have suffered much attrition and water-wear.

The paper concludes by contrasting the flint tools of Thetford with those found in other parts of England, and comments upon their probable use and adaptation.

On the Correlation of the Lower Lias at Barrow-on-Soar, Leicestershire, with the same Strata in Warwick-, Worcester-, and Gloucester-shires, and on the Occurrences of the Remains of Insects at Barrow. By the Rev. P. B. BRODIE, M.A., F.G.S.

The author first described two sections of the "Insect and Saurian" beds at Barrow-on-Soar, not previously noticed. These were compared with other adjacent sections, and the variations in the strata duly noted. The Insect beds were shown to occupy their normal position; but the thickness of the latter was not so great in Leicestershire as in Warwickshire. Hence a considerable thinning out of the Lower Lias in this direction was inferred. The Insect-bed were believed to extend into Nottinghamshire, and they have been also observed near Cave in Yorkshire. It remains to be proved whether the "Rhætic series" is present beneath in Leicestershire and Nottinghamshire as in Warwickshire. It has been lately detected near Gainsborough, in Lincolnshire. A general comparison was then given of the lower Lias in the county of Leicester with the same series in Warwick, Worcester and Gloster. The insect limestones were shown to be of much economical value in making hydraulic lime and for other purposes. Several faults on a small scale were noticed both at Barrow and at Wilmcote, in Warwickshire, in this zone. The characteristic fossils were pointed out; and it appeared that saurians and fish were abundant, more so at Barrow than Wilmcote; and the remains of insects were now for the first time indicated there, though they had been long since discovered in the same division in Yorkshire. It was argued in conclusion, that these lower Liassic limestones have a very extensive horizontal range, and are characterized by the remains of insects throughout, which really distinguish them far better than the Saurians, which have a much wider vertical

range.

On the Drift Deposit on the Weaver Hills. By E. BROWN.

On the Occurrence of the Rhætic Beds, near Gainsborough and the surrounding Strata. By F. M. BURTON.

Gainsborough is situate at the foot of a moderately steep escarpment of the Keuper or uppermost division of the Triassic system.

This escarpment consists of the usual beds of the series, yellow and blue marls alternating with brown and grey sandstones and beds of gypsum; the latter presenting both the granular and fibrous varieties. Owing to the operations of the Great Northern Railway Company, who are lowering the gradients of their line to Lincoln, a fine section of Rhætic beds has been exposed at Lea, about two miles from Gainsborough, where the lowest bed of the series, containing Avicula contorta, bones, and coprolites, is seen resting unconformably, though with parallel stratification, on the blue marls of the Keuper. This is followed by a band of black shale nearly unfossiliferous, above which comes the bone-bed, a narrow band full of worn bones, teeth, scales, and coprolites, imbedded in a cement of pyrites. This is followed again by a number of other beds of shale, sand, and limestone, of variable thickness and degrees of hardness, the highest at present exposed, a band of black shale about two feet thick, containing large Septarian nodules.

The whole series is highly pyritous, and contains Avicula contorta, Pullastra arenicola, with teeth of Hybodus, Acrodus, Sargodon, Termatosaurus, and other Rhætic fossils in abundance.

The Rhætic beds are capped by a stratum of drift which covers the surrounding country, and through which the cutting passes to Marton Station, about three miles from Lea, where a fine and very fossiliferous section of lower lias is laid bare.

Amongst the specimens found there are Septastræa Fromenteli, Montlivaltia Hameii, Pleurotomaria Anglica, Turbo elegans, Lima Hettangiensis, several species of Ammonites, and others.