produce no mineral change in the beds of limestone resting on them, it is inferred that the whole group is one formation, which has originated in the simultaneous action of aqueous and igneous causes long continued." Again, he maintains, "that many rocks, which now have a perfect porphyritic structure, were so far aqueous deposits, that they had been spread out into beds by the action of the sea, and that their actual structure (though certainly metamorphic) was not the effect of torrefaction or of heat emanating from any eruptive or igneous centre. On the contrary, that the natural temperature at great depths, combined with great pressure long continued, was a cause quite sufficient to explain the phenomena of the old stratified plutonic rocks," The only important modification which I venture to propose in this statement is, that we must distinguish between the aqueous causes really simultaneous with the igneous; viz. the water or steam present in the rock when undergoing metamorphic changes at great depths by heat and pressure, and from the aqueous causes acting long before, when these beds were deposited as true rudimentary strata at the bottom of the ocean.

If the positive evidence, then, is strong in favour of these rocks being metamorphic, I think the negative evidence is not less so. In regions where igneous rocks abound which are clearly eruptive, we have many characteristic marks of their origin. They have a distinct mineral character and structure; they do not graduate into slaty rocks. We have distinct evidence of their overflowing neighbouring strata. We have distinct evidence of the manner of their eruption from below in the presence of many vertical dykes.

None of these phenomena are observed in the Lake District, as regards the porphyries alternating with the slates. The only difficulty to be accounted for, I think, is the great thickness of some of the slaty beds, which have remained unaltered whilst other beds above them have been changed by the action of the same heat into porphyry.

It is evident, that if the different beds can be shown to be of different degrees of fusibility, this circumstance would be at once accounted for; and I have made some experiments to test this point, and also on the effects of fusion and slow cooling in producing metamorphic effects upon rocks.

The first experiment was made for me by Mr. J. P. Wood, of Leeds, on clayslate, greenstone porphyry, and greenstone roofing-slate, all reduced to fine powder, and about lb. of each placed in three crucibles in a common air-furnace, and gradually heated. At a good red heat the porphyry puffed up, fused, and ran over the edge of the crucible in the shape of a brown glassy slag; at a white heat the clayslate fused into a grey glassy slag; and, lastly, at a strong white heat, the roofingslate also fused into a black glassy slag. Thus the slate rocks appear to be decidedly less fusible; less easily acted upon by heat than the porphyries. The same result was obtained in fusing clay-slate, Skiddaw granite, and greenstone porphyry in a common reverberatory furnace; the stone being broken into pieces, about the size of those used for road-making, a white heat was required to fuse them, but the granite and porphyry melted much more readily and completely than the clay-slate. These simple experiments may be sufficient to prove a difference in the fusibility of the slaty and porphyritic beds, which would account for the latter undergoing changes by the same heat which would merely barden the former.

I next endeavoured to ascertain the effect of pressure combined with heat on the fusion of rocks, with the very able and zealous assistance of Messrs. Kitson and Hewitson, of this town. These experiments, which are attended with great difficulty, and require the patient endurance of a good many partial failures before a successful result can be obtained, are as yet only in progress.

Some results, however, may be seen in the specimens on the table. The powdered granite, clay-slate, and porphyry were enclosed in strong iron tubes, well consolidated to begin with by hydraulic pressure, then screwed up and heated to a red heat in an air-furnace, and then slowly cooled.

The result is a compact mass of distinctly stony texture approaching to slaty greenstone, quite different from the porous glassy slags produced by fusion without pressure. The fusion has taken place at a lower temperature under pressure.

I next tried the effect of fusion of a large mass of granite, in this case from the Charnwood Forest in Leicestershire, which happened to be most easily procurable. This was done in a reverberatory furnace constructed for the purpose by Messrs. Kitson and Hewitson, but the accidental failure of a portion of the furnace in the course of the experiment partially spoiled the result. The specimens, however, show a distinct passage from a perfectly glassy to a stony texture, and apparently even to a porphyritic structure by the development of crystals.

There are also specimens of the glassy texture, which by exposure to heat just below fusion in close tubes for two or three weeks, are changed to a stony texture; also of the powdered rocks enclosed in a strong iron tube, and buried in the large mass of granite when in a state of fusion in the reverberatory furnace.

The great desideratum, however, is the application of heat under high pressure with the presence of water, which must have been the condition, as remarked by Sedgwick, of the metamorphic rocks. My attempts in this direction have not yet succeeded. It is no easy matter to construct any sort of vessel capable of keeping red-hot water in safe custody.

Photographs of the Quarry of Rowley Rag at Ponk Hill, Walsall.
By WILLIAM MATHEWS, F.G.S.

The well-known basaltic capping of Ponk Hill in the South Staffordshire coalfield is being so rapidly worked away, that it has seemed desirable that some record of its structure should be preserved. With this view the photographs laid before the Section have been taken; they represent the whole of the face of rock now being quarried, from which the original structure of the mass may be easily ascertained. It formed when entire an irregular dome, communicating below with the extensive horizontal sheet of basalt intruded between the coal-measures, and consisted of two distinct sets of columns.

1st. An interior cylindrical group of very perfect vertical columns, rapidly thinning and arching over at the top some distance below the vertex of the dome.

2nd. Another group originating at the summit of the first, dipping down over their arched extremities, and then curving upwards so as to strike the exterior of the dome nearly perpendicular to its surface.

The columns are all situated in vertical planes passing approximately through the axis of the dome.

On Triassic Beds near Frome, and their Organic Remains.
By C. MOORE, F.G.S.

The author stated he became aware of the probable presence of Triassic beds in the neighbourhood of Frome, by finding a slab of conglomerate containing teeth of Acrodus, Hybodus, and Saurichthys on a roadside heap of carboniferous limestone. He at once examined the district for their discovery without success; but more recently was fortunate enough to find fissures of the carboniferous limestone at Holwell, filled with a similar conglomerate, the organic remains in which evidenced its Triassic origin.

In describing the physical features of the district, the author remarked that Frome was situated on the extreme south-eastern boundary of the Somersetshire coal-field, and that just north of that town the old red sandstone, with a narrow belt of carboniferous limestone lying on its side, might be seen emerging from beneath the inferior oolite. To the west the carboniferous limestones again appear in several pretty combs leading to Mells, Vallis, and Whatley, in the latter of which the Holwell quarries are situated. In the quarry opposite this village the limestone is worked to a depth of 35 feet. A fissure about a foot in breadth, commencing under a thin capping of vegetable soil, may be here observed, taking an irregular direction to the bottom of the quarry, where it increases to 10 feet in breadth. This is in part filled with vertical lamine of mottled yellow, grey and blue stone. A quartzose sand also prevails, sometimes indurated, but often friable; in which case, the imbedded organic remains may be readily detached.

First amongst these the Reptilia deserve notice, some of which belong to the Thecodont order which includes the Thecodontosaurus and Palæosaurus. Of the former, the author has obtained several teeth and vertebræ, and also several bony scutes or scales, which renders it probable one of the saurians of this period was covered with a bony armour like the Teleosaurus of the lias. These genera were originally described by Messrs. Riley and Stutchbury, from fragmentary specimens obtained from a conglomerate near Bristol, which has hitherto been considered to belong to the Permian period or to the dolomitic conglomerate, but from its precise lithological similarity to that of Holwell there can now be little doubt it belongs to the Triassic period. In referring to the absence of the Muschelkalk in this country, the author stated he had the pleasure of announcing, that, although the precise equivalent of that formation had not yet been satisfactorily made out, still in the presence of the teeth of another saurian-the Placodus-he had obtained the first indications of the fauna of that deposit being represented in England.

Important as were these indications of Reptilia, the fish remains from these conglomerates were probably of equal interest. They belong to the genera Acrodus, Hybodus, Saurichthys, Lepidotus, Gyrolepis, probably the Ctenoptychius or Petalodus of Owen, and some minute palates allied to Chomatodus, a genus not yet found higher than the carboniferous limestone. Teeth of the Acrodus, of several species, are very abundant, the next prevailing genus being the Hybodus. There are also some very peculiar thorn-like spines of not less than ten distinct varieties, belonging to some fish as yet undetermined, to the dermal coverings of which they were probably attached. So wonderfully preserved are some of these fish remains, that the author had been enabled to extract a jaw from the matrix, which, though not more than the eighth of an inch in length, contains all its teeth, thirty-four in number; and in another instance, a palate a quarter of an inch in length still retains seventyfour teeth, and shows blank spaces from which sixteen others had been lost.

The only evidence the author has yet obtained of regularly stratified Triassic beds is in the Vallis Vale, where there are several large quarries of carboniferous limestone, on the up-turned edges of which the inferior oolite lies horizontally, and is usually in immediate contact. This, however, is not the case in one near Hapsford Mills, where the following thin bands of Trias are found. Immediately on the carboniferous limestone, which is here quarried to the depth of 20 feet, occurs a bed of blue clay 4 inches in thickness, which yielded part of a Thecodont vertebra, fish remains identical with some from the Holwell conglomerate, and the teeth of several spines of Acrodi peculiar to this bed. It also yielded valves of Chiton and Pollicipes, with spines of Pseudodiadema and stems of encrinites, together with Ostrea, Lima, Avicula, and other shells. Succeeding this blue clay, is a bed of horizontal conglomerate 2 feet thick, made up of rounded pebbles, from the size of an egg downwards, and containing a few fish teeth and scales. Above is another band of blue clay 4 inches in thickness, passing into a grey concretionary clay 12 inches thick, neither of which has yielded any organic remains; and resting on these next succeed rubbly beds of inferior oolite, having a thickness of 12 feet.

Various other Mollusca have been obtained by the author from the beds above noticed, including Spirifer, Terebratula, Rhynchonella, Lingula, fragments of the large Discina Townshendi, which the author believed to be a triassic shell, Pecten, Belemnite, &c., and a single claw of a crustacean.

Note. Since reading the above paper, it has been the author's good fortune to discover three unmistakeable mammalian teeth identical with the Microlestes antiquus of the Upper Trias of Wirtemberg, being the earliest evidence of mammalian remains yet found in this country.

Some Results of recent Researches among the Older Rocks of the Highlands of Scotland. By Sir R. I. MURCHISON, F.R.S.

The first part of the paper consisted chiefly of a confirmation and extension of views which the author had laid before the Geological Society in the preceding session. These views are, that the fundamental gneiss of the N. W. Highlands, being older than any stratified rock of England and Wales, is overlaid unconformably by sandstones and conglomerates of great thickness, which, occupying lofty mountains, represent the Cambrian rocks of South Britain; that these are surmounted transgressively by quartz

rocks and limestones containing Lower Silurian fossils, or that the last are succeeded by micaceous schists and flagstones often passing into a younger gneiss.

The second part of the communication related to the Old Red Sandstone, properly so defined, as exhibited on the east coast, between the Orkney and Shetland Islands on the north, and Banffshire and Morayshire on the south, various points of which the author visited last summer. In Caithness and the Orkney Islands, accompanied by Mr. Peach, the author made various interesting additions to his former knowledge, and profited by the researches of Mr. Robert Dick of Thurso. His belief was sustained that the ichthyolitic flagstones of Caithness and the Orkneys, with their numerous fossil fishes, constitute the central member of the Old Red series, the lower part of which is made up of powerful conglomerates and a very great thickness of thin-bedded red sandstone, the whole being composed of the detritus of the more ancient crystalline rocks. The central flagstones are surmounted by other sandstones, rarely red, and usually of yellow colour, which occupy the promontories of Hoy Head, Dunnet Head, &c.

The chief additional data which had been gained by Sir Roderick during his last visit were owing, in the first instance, to a discovery by Mr. Martin of Elgin, of a large bone in the same beds at Lossie Mouth, which had formerly afforded large scales of the supposed fish, called Staganolepis by Agassiz. On visiting these quarries with the Rev. G. Gordon, he was so fortunate as to discover other portions of this large animal; so that comparative anatomists may determine whether it be, as the author believed, really reptilian. The existence of reptiles during the formation of this deposit is, indeed, established beyond a doubt; since many slabs have long been found in the coast quarries of Cummingston, in which are the footprints of both large and small reptiles, each footprint having the impression of four or five claws to it. A slab, transmitted by Capt. Brickenden, is in the Geological Society's Museum, and others have recently been sent to the Museum of Practical Geology, London, as contributions from Mr. P. Duff of Elgin, and other persons. The presence of large reptiles, as well as of the little Telerpeton, in a deposit which all geologists have hitherto considered to be an upper member of the Old Red Sandstone, is therefore established.

After noting certain fossil fishes which occur in parts of the Duke of Richmond's estates in Banffshire, the author proceeded to review the relations of the great masses of sedimentary deposit lying along the eastern and southern faces of the crystalline rocks of the Grampians, which have been hitherto classed as pertaining to the Old Red Sandstone, though he does not pretend as yet to be competent to describe their detailed features. On these points, however, which Mr. D. Page is working out with ability, he begs to offer the following suggestion. The true base of the Old Red Sandstone, properly so called, is seen in Shropshire and Herefordshire to be a red rock, containing Cephalaspis and Pteraspis, which gradually passes down into the grey Ludlow rock; and in both of these contiguous and united strata, remains of large Pterygoti, but of different species in the two bands, are found. Now, although the Arbroath paving-stone, and the grey rocks ranging to the north of Dundee, lithologically much resemble the uppermost Ludlow rock, they contain the Cephalaspis Lyellii as well as Pterygoti, and must, under every circumstance, be viewed as the base of the Devonian rocks. In speaking of the lowest member of the Old Red Sandstone, as characterized by the Cephalaspis, the author expressed his conviction, that in the north-eastern Highlands and Caithness that zone is represented as above mentioned, by the vast thickness of thin-bedded red sandstone and conglomerates, which underlies the bituminous flags of Caithness.

The author, who had recently visited Dura Den, in Fifeshire, in the company of Lord Kinnaird and the Rev. Dr. J. Anderson, whose work, 'The Course of Creation,' is well known to geologists, declared that there could be no doubt that the yellow sandstones, that tract in Fife which pertains truly to the Old Red group, are entirely subjacent to the lowest carboniferous sandstones, and are probably of the same age as the upper yellow sandstones of Elgin. A drawing, prepared by Lady Kinnaird (the splendid specimen having been placed in the museum at Rossie Priory), of the fossil fish Holoptychius, nearly three feet in length, which was found on the occasion of this visit on the property of Mrs. Dalgleish, was exhibited; and as this form abounds

* This large species has proved to be the H. Andersoni, Ag.

in the lower and redp ortions of the deposit, and also occurs in the overlying yellow sandstones, associated with other old red ichthyolites, the age of the deposit is clearly substantiated.

In conclusion, Sir Roderick said that this communication must be considered as a rehearsal only of what he hoped would be done with more effect next year at Aberdeen, when further observations might lead him either to confirm or modify that portion of his views which relates to the age of the Elgin sandstones. In the mean time, the fundamental reform of the North Scottish series is above narrated, proving that the ascent from rocks on the west coast, which are unquestionably older than any in England and Wales, through Cambrian and Lower Silurian rocks to the much younger "Old Red Sandstone" of the east coast, is firmly established. The communication was illustrated by several geological maps, to indicate the successive steps in knowledge, including an old one coloured by himself thirty-one years ago, the maps of M'Culloch, Nicol, and Knipe, and a map of Sutherland, which the author had coloured during the summer. Besides large diagrams, there were sketches of the mountains and lochs of the west of Sutherland by Miss Charlotte Dempster.

On the Age and Relations of the Gneiss Rocks in the North of Scotland. BY JAMES NICOL, F.R.S.E., F.G.S., Professor of Natural History in the University of Aberdeen.

The author expressed his regret that in one point he was compelled to differ from his distinguished friend Sir R. I. Murchison. He could not regard the entire gneiss forming the central regions of Ross and Sutherland as of younger age than the red sandstone and quartzite of the west coast (Cambrian and Silurian of Murchison). He described a section from the Gairloch to the Moray Frith, and showed that the red sandstone and quartzite resting on the gneiss of the west, were cut off by a mass of felspar-porphyry and serpentine from the supposed overlying rocks on the east. He had traced a band of similar igneous rocks at intervals for a hundred miles, from Loch Eriboll to Skye, and had observed other indications of fracture and convulsion along this line, as shown in the section exhibited. He therefore concluded that the overlap of gneiss on quartzite might be occasioned by a slip or convolution of the strata, and not mark the true order of superposition. He also stated, that the unconformability of the quartzite to the red sandstone (Cambrian) which he had described at Assynt and on Loch Broom, did not seem to occur in Gairloch, where the two deposits, as seen in great sections on the escarpments of the mountains, appear quite conformable; the red sandstone, however, extending far beyond the quartzite on the west. He further pointed out, that, in the central region of Scotland, from Aberdeenshire to Argyllshire, the great formation of gneiss, with limestone and quartz rock, overlies the mica slate, and does not dip under it, as usually represented. In particular, the gneiss of the Black Mount and Breadalbane Highlands appears to form a wide synclinal trough resting on both sides on mica slate, and thus to be an overlying and younger formation.

On the Comparative Geology of Hotham, near South Cave, Yorkshire. By the Rev. T. W. NORWOOD, of Cheltenham.

The village of Hotham is upon the lower lias; but all the secondary rocks of this part of Yorkshire, from the new red sandstone to the chalk inclusive, may be seen in its immediate neighbourhood. Their course is nearly N.N.W. At Hotham proper we are only concerned with the lias and inferior oolite; to them therefore these remarks are limited.

I. Between North Cave and South Cliff the lower lias "limestones and shales" present to the plain their usual elevated outcrop, and exhibit plentifully their characteristic fossils-Gryphea incurva, Lima gigantea, Ostrea liassica, Modiola minima, and many other familiar forms. The "Bone-bed" and " Insect-bed" appear to be wanting. The lias passes conformably, and somewhat suddenly, into the sandy beds below it.

A great destruction has happened to the lower lias in this locality. The north side