association of interest, and lay there unnoticed till last year. It had then become more opaque, and consequently of more interest to him. It has now all the appearance of a solid crystal of gold, and for which it has frequently been taken. The colour is pale, but he had observed that all gold found in quartz in that locality is light coloured, owing to the presence of a large percentage of silver, sometimes as much as 20 per cent.

He exhibited, also, some ounces of water-worn gold, some pieces weighing from 20 to 30 grains each, recently found in the Cain, a tributary of the River Mawddach, north of Dolgelly, and also a very rich specimen, broken from a quartz-lode at the Gwynfynnydd mine, adjoining the Cain and Mawddach rivers. He said he brought before the Section as mineralogical facts:-that of the change of the crystal, that the gold where the crystal was found is of 14 carats fine only, that from the quartz-lode at Gwynfynydd 18 carats fine, and the water-worn gold from the Cain and Mawddach 23 carats fine-giving them as facts open to a good deal of interesting speculation.

On Sections of Strata between Huyton and St. Helen's.
By CHARLES RICKETTS, M.D., F.G.S.

The exposures made in the formation of the new railway between Huyton and St. Helen's, whilst confirming the general accuracy of the maps of the Geological Survey, have disclosed important features which would not otherwise have been determined.

In the Lower Coal-measures or Gannister beds, a little north of, but somewhat lower in the series than, those in Huyton Quarry, a succession of beds of sandstone, shales, and clay was displayed, surmounted by a bed of coal a foot and a half thick, probably the equivalent of the " Mountain Mine" coal formerly worked at Knowsley. As the line to the south of Prescot crosses the Upper Coal-measures, several outcrops of coal are exposed, viz. " the Bastions," in the situation marked upon the map; a bed called in the six-inch map "Little Delf," and the "Sir John" coal, about one hundred yards to the eastward of the places given from information as the position of their outcrop; and at the site proposed for the Prescot Station, the two beds constituting the "Prescot Main" coal, a short distance beyond which, and sixty yards from the Rainhill road, a considerable north and south fault occurs, not marked upon the map, which throws down to the east purple and mottled sandstones and shales of upper beds of the Coal-measures; these continue as far as the Survey boundary fault, by which the Lower Bunter is thrown down to the east.

As on the formation of the Liverpool and Manchester Railway the presence of Coal-measures was discovered near Whiston, so likewise in a situation marked upon the maps as Lower Bunter, there occur two small areas of purple Coal-measure strata similar to those near the Rainhill road, having intervening beds of Triassic sandstone, which have been thrown down by faults.

The boundary fault of the St. Helen's Coal-field is seen at Thatto Heath, having an intermediate step-fault on the west or downthrow; it has likewise caused a considerable amount of fracture and displacement in the Pebble-beds or Middle Bunter. The Sutton-Heath fault is crossed by the railway where the two beds forming the "Ravenhead" coal are cut off on its downthrow; a little below the lower or "main" coal trees were seen in situ, and the Rev. H. H. Higgins has obtained from the same locality numerous specimens of the stems, leaves, and fruits of Calamites, and also of Lepidodendron, with ferns &c.; also a beautifully preserved wing of an Orthopterous insect: these have been deposited in the Liverpool Museum.

At the entrance to the deep cutting in the Pebble-beds near Scholes Farm, wherever the surface is covered with the sands and clays of the Boulder-clay period, it remains beautifully planed, grooved, and striated, the striae being from southeast to north-west.

In the Lower Bunter sandstone, previously alluded to, there are several fissures without much displacement of the beds, the interstices being filled with a débris

consisting of subangular and rounded fragments from the Coal-measures and the Triassic sandstone, as well as liver-coloured and quartz pebbles from the Middle Bunter, and likewise granite, porphyry, greenstone, and other pebbles derived from the Boulder-clay, one of which affords an excellent example of glacial markings. It may therefore be inferred that these fissures must have been formed during the recent or at least the postglacial period.

Mr. C. Smith exhibited an Orthopterous insect.

On the recent Formation of Gravel-beds resembling Middle Drift.
By G. JOHNSTONE STONEY, M.A., F.R.S.

On the east coast of Ireland, extending south of Dublin from Killiney to Bray Head, and from Bray Head to Greystones in the county Wicklow, there are considerable cliffs of Drift exposed to view. They consist of (1) masses of amorphous glacial clay, usually containing an abundance of striated limestone boulders and fragments of shells; (2) gravel, which is almost unstratified, containing a few striated boulders and fragments of shells; and (3) stratified beds of gravel and sand, without striated boulders and with but very few fragments of shells. The stratified beds have usually been regarded as Middle Drift, the other beds being treated as Upper Glacial Drift or Lower Glacial Drift, according to their position.

The author had carefully examined these formations from Bray Head to a little south of Greystones, and had satisfied himself that the undoubtedly glacial deposits are to the present day in process of being transformed into the stratified beds of gravel and sand, which have been usually referred to Middle Drift.

The Drift rests directly on argillaceous slates of the Cambrian formation; and the first thing which attracted attention was that all the spring water of the neighbourhood is hard, containing an abundance of salts of lime. These could only have been obtained from the limestones of the Drift, and consequently indicated that a sensible amount of change is going on in it. This led the author to investigate further, and he then found evidences of change everywhere and unmistakable. But it will be most useful to confine this record to the appearances in two situations, which can be without difficulty identified by any person who may wish to reexamine the ground.

Under the railway station at Greystones, which is built close to the shore, a cliff of glacial clay with abundance of striated boulders will be found. It rests directly on the Cambrian slates, which are also exposed to view. Immediately in front of the railway station the clay reaches to the surface of the ground; but 80 or 100 yards further south beds of stratified gravel will be found above it, the stratification being usually oblique to the surface of contact of the gravel and clay. Here it will be easy to see evidence that rain when it falls soaks quickly through the gravel, and then travels along the upper surface of the clay. In doing so it penetrates the clay to a certain distance, from 2 to 6 inches, altering its colour from a dirty blue, which is the prevailing colour of the glacial clay at this spot, to a light fawn colour. If this stratum of clay out of which the colour has been discharged be dug into, the remains of limestone boulders will be found scattered through it, which have also been attacked by the water. There usually remains either a powdery mass of the insoluble matter of the boulder, or such a mass with a core of some fantastic shape, which is the part of the limestone that has not yet been dissolved away. In a few instances specimens were found in which one side of the stone had been sheltered from the water, and still retained its glacial markings. Moreover some of the clay is washed forwards when the water travels over it, for wherever the water dribbles out at the surface of the cliff it carries clay out with it, Here, then, we have an instance in which the so-called Lower Glacial Drift is being in part corroded or washed away all over its upper surface; and the portions that remain are being added on to the lower surface of the overlying Middle Drift. The part which is being converted into Middle Drift appears to consist principally of the insoluble stones of the glacial clay, and of such central portions of the larger limestones as may outlive the corroding process.

At this station, wherever the rock is exposed to view, water will be found also, oozing out here and there from the face of the cliff between the glacial clay and the underlying rock. Where this occurs, abundant specimens of the corroded limestones are to be met with; and no doubt if the passage of water were sufficiently prolonged, it would in time lead inevitably to the formation of gravel-beds between the clay and the rock. But the percolation which was observed appears to be of too modern a date. It probably began after the existing cliff was formed by the advance of the sea.

A case, however, in which Upper Glacial Drift has undoubtedly been converted into Middle Drift, will be found at the south end of the Ladies' Bathingplace at Greystones. Here the upper part of the cliff consists of glacial clay with a few striated boulders, and below it there are imperfectly stratified beds of sand and gravel. These porous beds communicate with the surfacesoil by means of a chimney-like passage filled with gravel, which is exposed in the cliff, and through which rain gained access to the beds below. These beds bear evidence that, before they were cut across by the sea, they formed part of a subterranean reservoir, in which slowly flowing water was confined between the rocks beneath and the glacial clay above, the lowest layer of the glacial clay to the depth of several inches having acquired a structure which is stratified parallel to its under surface. This stratified structure is continued along the clay walls of the passage by which the rain had access to the porous beds. In this case the corroding and transporting action of the water upon the underside of the glacial drift has probably been suspended since the subterranean reservoir was tapped by the encroachment of the sea; but the appearances clearly show that it had before that time been going on, that the water in its passage had been corroding or carrying away some constituents of the Upper Glacial Drift over its under surface, and that the residue which remained became an accession to the underlying beds of gravel and sand.

These particular spots have been pointed out, because they can be easily identified by other observers; and abundant confirmatory evidence will be found all along the three miles of coast examined by the author. In some places isolated masses of clay will be found in the gravel-beds, which may be presumed to be outstanding portions of the glacial clay; and in all places the ratio of the limestones to the other kinds of stone is much less in the gravel-beds than in the glacial clays, which is the state of things that would naturally arise if the gravel-beds have been wholly formed out of glacial deposits by the prolonged action of the causes which we find still in operation.

There is also evidence to show that the stratification of the gravel-beds is due to causes still existing; for in the places where there is the most unmistakable evidence that Middle Drift is to this day being formed at the expense of glacial drift, it was found that the stratification of the gravel-beds was continued almost into contact with the glacial clay, and therefore through the parts most recently converted. But this need present no difficulty. An old mill-race, with a mound along one side of it, has lately been removed to make way for the extension of Dublin towards Sandymount. The mound when cut across presented as fully developed a stratified structure as is usually seen in natural gravel-beds. And what made the case conclusive was that the distribution of the materials was in most places wholly different both in kind and degree from what the original piling of them together could have occasioned. It must therefore have been produced subsequently, and it was interesting to observe most of the main features of natural stratification reappearing in it, with their unconformable beds, separation of fine from coarse materials, and so on.

A very simple experiment will show how much may be effected even in a short time by the percolation of water through gravel-beds. Pour a few cans of water upon sand which consists of particles of various degrees of fineness, and if a little cliff be then made in the wet sand, it will be found to be already stratified in a very considerable degree.

On the Physical Geology of the Bone-caves of the Wye.

By the Rev. W. S. SYMONDS, M.A., F.G.S.

Fossil bones of the exinct mammalia have been discovered in "King Arthur's Cave," situate in Great Doward Wood, on the right bank of the Wye, between Whitechurch, near Ross, and Monmouth. They were forwarded to Prof. Owen, and were determined by him to be molar teeth of E. primigenius, molar teeth of Rhinoceros tichorhinus, gnawed astragalus and bones of R. tichorhinus, molar teeth and bones of Equus fossilis, upper molar and astragalus of Bos primigenius, shed antler of Reindeer (Cervus tarandus), right upper canine of Hyæna spelaa.

These fossil bones are from a cavern in a locality rich in caves in the mountain limestone, now elevated to a considerable height above the river Wye, but in which fossil bones of the extinct mammalia had not hitherto been found.

Arthur's Cave has evidently been the den of the great Cave Hyæna, as evinced by the gnawed state of many of the bones, and the remains of that animal itself. The physical geology of the district was described by the author of the paper.

On the Occurrence of Seams of Hard Sandstone in Middle Drift of East Anglia. By J. E. TAYLOR.

A Census of the Marine Invertebrate Fauna of the Lias.
By RALPH TATE, F.G.S.

On the Diamonds of South Africa. By J. TENNANT, F.G.S.

On the Occurrence of Pebbles and Boulders of Granite in Schistose Rocks in Islay, Scotland. By JAMES THOMSON, F.G.S.

The author described the different rocks exhibited in a section across Islay, from Port Nahaven on the west to Port Askaig on the east, which principally consist of gneiss, chlorite and mica-schist, quartzites and limestone. There is a diversity of opinion as to the proper position of these rocks; some consider them of Laurentian, while others think they are of Cambrian age. The author was inclined to think they belonged to the latter period. At Port Askaig there is a precipitous cliff of quartzite about 70 feet in height, made up of about one hundred thin bands varying from 1 to 20 inches in thickness. Underlying this quartzite there is a mass of arenaceous talcose schist, showing faint traces of stratification, containing fragments, some angular but mostly rounded, of all sizes, from mere particles to great boulders of granite, resembling the granite of the Island of Mull. Similar rocks do not occur in the Island of Islay; and Mull being at a considerable distance to the north, with a deep sea between the two islands, he suggested the probability of the granite having been transported by the agency of ice.

These deposits resemble the boulder drifts of more recent times, in the following respects-first, in the absence of stratification in one part of the section, which in another shows signs of regular deposition; secondly, in the close proximity of fragments of far transported rock, varying in size from minute fragments to large boulders; the origin he ascribed to the mass having been deposited in a tranquil sea of mud, sand, and blocks from melting drift-ice. The absence of stratification in one part of the section while it is present in another, may be accounted for by the disturbing action of icebergs, when stranded in the soft plastic mass, in parts of the sea of limited depth. He also stated that pebbles of granite had long been sought for in the conglomerates of the Old Red Sandstone; but in no part of Scotland had it been found in rocks of that age, consequently it was inferred that the granite of Scotland was posterior to the deposition of the rocks belonging to that period. The discovery of fragments and boulders of granite imbedded in these deposits, furnish adequate proof that the age of granite cannot be restricted, and that glacial action was not limited to any special geological period.

On a Diagram of the Earth's Eccentricity and the Precession of the Equinoxes, illustrating their Relation to Geological Climate and the Rate of Organic Change. By ALFRED R. WALLACE, F.R.G.S.

The author exhibited a diagram of the eccentricity of the earth's orbit and the precession of the equinoxes, from which he deduced certain important views as to the climates of past geological ages and the changes of organic life. During the past three million years the eccentricity has been almost always much greater than at present, on the average twice as great, and for long periods more than three times as great. It was shown that when the eccentricity was greatest the heat received from the sun at the greatest and least distances was as 3 to 4; and, owing to the precession of the equinoxes, the winters of the northern hemisphere would be rendered intensely cold and much longer for periods of 10,500 years, while during the alternate periods the winters would be mild and short, the summers cool and long, leading to an almost perpetual spring. We thus have cold or glacial epochs for about 10,000 years, alternating with mild epochs for the same period, whenever the eccentricity was high, and this was the case for fully the half of the last three million years; and, as such alternations must have occurred during every glacial epoch, the fact of intercalated warm periods and the migrations consequent on them, which have been detected by geologists, must be looked upon as the normal condition of things. But during the last 60,000 years (probably the whole time elapsed since the close of the last glacial epoch) the eccentricity has been very small, and the alternations of climate and consequent migrations very slight; and as Mr. Darwin holds that alternations of climate are, by means of the consequent migrations, the most powerful cause of modifications of species, there must have been a comparative stability of species during that period of time, from which alone we obtain our idea of the rate of specific change. This idea will therefore be erroneous; and the rate of change during past geological ages may have been, and probably was, much more rapid than has hitherto been thought possible. During three million years before and one million after the recent epoch, no less than 130 alternations of climate occurred (each of 10,000 years' duration), when the eccentricity was more than double what it is now; and these incessant changes were thought, on Darwinian principles, to supply a vera causa for a rapid change of species, and thus enable us considerably to reduce the duration of geologic periods, which had heretofore been measured by data derived from the period of organic stability since the last glacial epoch.

On the Organization of the Stems of Calamites.

By Professor W. C. WILLIAMSON, F.R.S.

The author pointed out the unity of type observed amongst the British Calamites, and the consequent improbability of the existence anywhere of two types (the one Cryptogamic, the other Gymnospermous), as believed by Prof. Adolphe Brongniart. He then described the various portions of the jointed stem, the centre of which is a cellular ring of fistular pith, having transverse dissepiments at the nodes. Around this is a woody zone, composed of wedges of barred and reticulated vessels. These wedges are separated from each other by large medullary rays, and smaller rays separate the constituent laminæ of each wedge, which latter spring at their innermost angle from a longitudinal canal running from node to node. The organization of these wedges, canals, and medullary rays was described in minute detail, their variations in several species being noted, as well as the differences between the arrangement at the nodes and at the internodes, which differences are often very characteristic. The structure of the epidermal layer, or bark, was then shown to be cellular; it consisted of an irregular parenchyma, with cells of variable dimensions. Its exterior appears to have been smooth, unlike the exterior of the woody groove zone, which, like the interior of the latter portion, was longitudinally fluted, the longitudinal ridges and furrows of each internode usually alternating at the nodes. The branches were shown to be of small size, being given off from the woody wedges exactly opposite the centre of each node, whilst the roots were described as originating from the lower extremity of each of the internodes at the