distance of 18 inches, giving the rock a mottled look. In other places along the shores of and over Killiney Hill, the granite, at its contact with the slates, exhibits a thin layer of well-developed crystals of mica.

In our present state of information regarding the chemical or mechanical action which would take place in a heated granite being brought on a large scale into relation with a cold mass of slates, it is difficult to account for the appearance which the granite presents at Killiney Park Quarry; doubtless the appearance which the mica now presents is the result of a re-arrangement of the crystals, and is, in short, a metamorphism.

General Sketch of the Districts already visited by the Geological Survey of India. By THOMAS OLDHAM, A.M., F.R.S., G.S., &c., Superintendent of the Geological Survey of India.

The labours of the Geological Survey of India have been conducted hitherto under great difficulties. More recently, however, the liberality of the Government of India has greatly extended the establishment of the survey, and Mr. Oldham trusted that their future progress would be rapid and effective. The only general sketch-map of the geology of India which they had was that published by the late Mr. Greenough. This was a work of great value, and gave abundant proof of the extent and labour of its author in its compilation. As might be anticipated under the circumstances, it was full of errors; and perhaps few could speak more confidently of this than himself. But at the same time it was a most valuable contribution, and would prove a most useful guide to future observers. The officer of the Geological Survey had examined several districts of considerable area in detached positions, and the results which he was able to lay before the Section might therefore appear less connected than he could wish. But every day would tend to unite them more closely; and his object was now simply to report progress, and to show that something had been done to elucidate the structure of India. Referring first to the districts to the east of the Bay of Bengal, the Tenasserim Provinces extend for about six degrees of latitude along the east shores of the Bay of Bengal. In breadth they seldom exceed more than one degree of lon-gitude. From Siam, on the east, these provinces are separated by an interrupted range of mountains, occasionally rising to 7000 or 8000 feet high, but the general height of which is to the north about 4000, diminishing in passing southwards to 3000 feet or less. The main direction of this range is north and south; this being also the general direction of the coast line, of the minor and outlying ranges of hills, and therefore of the rivers. The geological structure is tolerably simple, although at first sight apparently complicated, from the great disturbances to which the rocks have been subjected. The central range is of granite, occasionally, but not frequently of syenitic character; itself traversed by thick veins of large crystalline felspathic granite, and often along its outer edges, or near its junction with overlying slates, characterized by the presence of tinstone as an ingredient of the mass disseminated among the other mineral constituents. This granite axis is succeeded by highly metamorphic rocks of gneissic and micaceous character, themselves cut up by nume rous veins of granite, which, however, do not extend far from the junction. Upon these is a great accumulation of bluish and bluish-black earthy beds, thinly laminated, of thin-bedded grits, and of pseudo-porphyritic rock, the normal character of which is an earthy hard rock with small irregularly disseminated sub-crystalline felspar, passing, on the one hand, into slates, and, on the other, into grits, often coarse and conglomeritic. These harder rocks form all the higher grounds of the outer ranges of hills. This series, being best seen in the southern province of Mergui, has been provisionally called the "Mergui" series. The total thickness is about 9000 feet. It is succeeded unconformably by hard sandstones in thick and massive beds, with their earthy partings, generally of reddish tints, occasionally deep red and yellowish. A few beds are slightly calcareous, and in the upper portion a few thin and irregular bands of earthy blue limestone occur. Above these rest about 200 feet of soft sandstone in thin beds, upon which apparently rests the massive limestone of the country so largely seen near to Moulmein. The thickness of the entire group is about 6000 feet, and as some of its members are but seen in the northern province of Moulmein, I have provisionally called it the "Moulmein" series. To determine the age of the

older of these two groups (the Mergui) we have no data. The aspect of much of the rocks is very similar to the trappean ashes and felstones so abundant in the Silurian rocks of this country, while others are lithologically like Devonian; but these resemblances are very deceptive. The age of the Moulmein series is, however, tolerably defined by its organic contents. These appear to fix the age of the group as distinctly carboniferous. The whole of these rocks were, subsequently to their induration and disturbance, widely and greatly denuded, and on their upturned edges at intervals is found a series of conglomerates and sandstones and imperfectly coherent shales, with thick beds of coal, generally of lignitic character. None of the conglomerates are coarse; the sandstones are fine, gritty, and pebbly, or clean white quartzose grits; the shales thinly laminated; the coal itself thinly disposed in thin flaky laminæ, with earthy streakings marking its structure. In addition to the total unconformity of these rocks, the imbedded organic remains are quite distinct. They consist of dicotyledonous plants (leaves) belonging to the group of the Laureaceæ, and probably to the genus Laurophyllum of Göppert. In the thin papery shales which overlie the coal are also remains of fish (scales, &c.) of freshwater character; the whole referring the beds to a very recent epoch, probably corresponding in part to the pliocene of European geologists. It is curious to notice here the absence of any coal in the carboniferous rocks below, and its abundant presence in those newer beds. The total thickness of these beds does not exceed 900 to 1000 feet. They are never continuously traceable; they occur heaped up against and separated by the projecting ridges of the higher grounds, and must have been deposited when the physical conformation of the country was very similar to that now existing. They appear to be the result of a series of freshwater deposits, formed in small lake-like expansions along the lines of the great drainage valleys of the country; and to mark a line of general and greater depression between the main ridge of hills dividing Siam from the British dominions, and the outer ridges which occur between this and the sea. The direction of the main drainage of the country is determined, as already remarked, by the direction of these ranges, and is discharged into the sea through narrow rocky gorges, which have a direction nearly east and west, and which are due to lines of breakage and dislocation. To this is due the sudden alteration in the direction of the courses of the larger rivers, as may be seen on maps. Rocks similar to those situated in the Tenasserim provinces extend northwards up the course of the Salween River, and into the adjoining districts of Burmah, to the north-east of Pegu. And, again, close to the capital of Burmah, and stretching nearly north and south, as far as examined, high ridges of metamorphic rocks are again met with, consisting of gneiss, micaceous schists, and highly crystalline limestones, occasionally of a fine white colour, and largely used by the Burmese for sculpture. But the great valley of the Irrawady is, throughout a very large extent of its course, bounded on either side by a thick series of rocks, chiefly sandstones, but with massive limestones also, which are locally rich in fossils, and which, from this evidence, may be clearly referred to the eocene period. These stretch on both sides of the river as far north as Pugahu, beyond which the higher grounds recede from the river banks; but they are in all probability continued thence into Munipoor, and so united with the nummulitic rocks of the Khasi and Cachar Hills. These rocks have been considerably disturbed and broken, but have a general and prevailing strike nearly north and south, which strike, throughout many miles, has determined the general course of the River Irrawady. Their thickness is considerable, certainly exceeding 5000 feet. Above these eocene rocks, and resting upon them with slight unconformity, is a series of beds of no very great thickness, characterized by an abundance of gypsum disseminated in thin layers and veins, and in the lower beds of which occur the deposits of clays and of vegetable matter, from which are derived the larger supplies of petroleum. These rocks are well seen at Senan Kyoung ("stream of foetid water"), and are traceable northwards to near Amarapura. In the beds which appear to form the uppermost part of this group, but which may possibly belong to another and distinct series, are found some of the fossil bones of the larger animals which occur abundantly in this district. About forty miles north of Amarapura we again meet with sandstones, shales, and coal, resting unconformably on the metamorphic rocks, and characterized by remains of dicotyledonous trees similar to, if not identical with, those found in the coal-yielding group of the Tenasserim provinces, and which are therefore referred to the same age (pliocene).

This series, so far as examined, proved of no great extent or thickness. We pass now to the Khasi Hills, which form a comparatively isolated range, rising suddenly from the great plains of Bengal in the south, and divided in the north by the valley of Assam from the great Himalaya or Bhotan range. On the southern face this range rises almost perpendicularly from the plains, which are continuous from the Bay of Bengal, with scarcely a perceptible change of level to the very foot of the hills, and, with the exception of a comparatively small thickness of metamorphic rocks at the base, are composed of nearly horizontal beds of sandstones, a few shaly layers, and limestone, long known for the abundance and beauty of the nummulites it contains. These beds dip slightly to the south, and die out towards the north, when the metamorphic rocks come to the surface in the hills. Disregarding here any details as to the older rocks, the age of the sandstones and limestones is unquestionably fixed by their organic contents, and therefore, also, the epoch of the coal, which is associated with them, as belonging to the great eocene period of geologists. No newer group of rocks is definitively seen in these hills. Along the southern face of the range there is evidence of a great dislocation extending for many miles, and possibly along the entire scarp, which has brought down to the level of the plains the rocks which are seen at the top of the hills. This line of dislocation has in all probability tended to give the nearly rectilinear direction of the escarpment; its date is fixed as at least subsequent to the formation of all the eocene rocks here seen. An older group of sandstones, considerably altered, is seen further to the north, within the hills, and also a series of highly metamorphosed schists and grits resting upon the gneissic and granite rocks; but the details of these are reserved. Passing thence still further to the north and east, at the base of the Sikkim Himalayas, under the hill station of Darjiling, another section was described. The great mass of the lofty hills is here composed of schistose rocks of various characters, considerably disturbed and contorted. These, although hitherto coloured similarly, and considered as of the same age, were decidedly different from, and more recent than, the gneissose rocks of the greatest portion of India. Near the base of the hills, and faulted against these rocks at high angles, there is a small extent of sandstone and black shales, which contain Vertebrata, Pecopteris, &c., similar to those occurring in the great coal-fields of Bengal. These fossils are peculiarly interesting, from the fact of their being changed into graphite, and occurring in beds which themselves have a very strongly marked graphitic character. They are of very limited extent; the greater portion of the sandstones, which in this section exhibit a thickness of some thousand feet, belonging to a series of much more recent date, and which has been subjected to a much smaller amount of disturbance and alteration. The exact relation of these, too, it has not been possible to observe. This upper group contains many large stems, in all observed cases prostrate, and in most cases giving evidence of great wear and long exposure previously to being imbedded; and in some of the finer and more earthy deposits an abundance of leaves occurs, of the same general character as those already noticed as occurring in Burmah and Tenasserim. This group was therefore provisionally referred to the same age (pliocene). No traces of the great nummulitic series had been observed in this district. In the more central portions of India three very large districts had been examined, to which he would now refer. One of these was to the south of Calcutta, in the district of Cuttack; the second included all the country between the great coal-field of the Damoodah, which had previously been mapped by Mr. Williams, and the River Ganges, extending northwards to Rajmahal and Bhagulpore; and the third extended along the valley of the Nerbudda from west of the Hosungabad to many miles east of Jubbulpur. For the details of the first of these he was indebted chiefly to his able assistants, Messrs. Blandford; for the last to Mr. Jos. Medlicott, who had very zealously worked it out, having to carry on the formation of a topographical map at the same time. In all these cases the sedimentary rocks, to which he would refer, formed portions of a series once more widely extended, and probably continuous over the whole country, now separated by denudation, from removal by which they have been in great part protected, by being faulted into and against the highly metamorphic gneiss, &c. which surround them. The Talcheer field extends for about 70 miles from east to west, with an average breadth of 15 to 20 miles, and is bounded both on the north and south by great parallel faults, the former of which has an aggregate throw of upwards of 2000 feet; these faults are not truly east and west, but to the

south of east and north of west. The section in ascending order of the basin shows at the base sandstone and blue shale, but slightly fossiliferous in thickness from 500 to 600 feet; over these is a series of shales and sandstones often micaceous, occasional beds of ironstone, and thin layers of coal and coally shale, giving a total thickness of about 1800 feet; and over these again is a distinct series of quartzose grits, conglomerates, and sandstones, in thickness from 1600 to 2000 feet. These three groups are unconformable each to the other; the unconformity between the two lower being, however, much less marked than that between the two upper. To the lower group, as having been first recognized and described in this district, the name of "Talcheer" series has been given; the second group, which, from its imbedded vegetable remains, was proved to be identical with the rocks of the extensive Damoodah coal-field when these were first described, has been denoted the “Damoodah” series; while the upper group, supposed to represent the great series of rocks, so magnificently seen in the Mahadeva Hills of Central India, has been called the "Mahadeva" series. Thus these series can be recognized in each of the extensive fields referred to, although with varying developments and thicknesses. At the base of the Talcheer series there is a remarkable bed, consisting of very large and only slightly rounded masses of granite and gneiss, imbedded in a fine silt, and occurring under such conditions as induce the opinion that the action of ground ice has been the cause of its formation. In the Rajmahal district, there is a very limited development of the lower beds, above which unconformably comes the Damoodah series, here exhibiting a greater extension upward than in Cuttack; but unfortunately the sequence of the rocks is interrupted by the intercalation of several successive floes of basaltic trap, the intervals between which have been marked by the continued and tranquil deposition of the mechanical rocks going on. These floes have been repeated six or seven times, and the phenomena of contact are in all cases marked; the upper layers of the mechanical deposits in contact with the trap being in all cases greatly altered, while the lower layers are in no cases changed, but rest unaltered on the degraded surface of the underlying trap. But while the actual physical sequence of the deposits cannot be here traced, the fact of their all belonging to the same great series is attested by the occurrence of some identical fossils throughout. A few species pass upwards through the series, but there is a very marked change in the general facies of the flora in the upper as compared with the lower portion of the group; the latter characterized by the abundance of Pecopteris, &c., the former by the abundance of zamia-like plants. The series, therefore, has been divided into Upper and Lower Damoodah rocks. For the details of the structure of the district, reference was made to the maps. In the Nerbudda district the series was less interrupted, and there also the same general results were obtained. The southern boundary of this great field was for a large part of its course produced by a great fault, having, quam proxime, the same general direction as that of the faults bounding the Talcheer field. The age, geologically considered, of these Damoodah rocks was briefly referred to. A large series of drawings of the fossil plants from them were exhibited, and the fact of the general oolitic facies of this group, especially of those from the upper beds, pointed out. The difficulty of the question was alluded to, especially in connexion with the discovery, on the one side, of several species identical with those found in these Indian rocks in the Australian coal-fields, associated with numerous animal remains distinctly referable to the lower carboniferous era; and, on the other hand, with the discovery in Cutch of other species, also identical with some of these Indian forms, in beds associated with animal remains, undoubtedly referable to the oolitic epoch. It must, however, be borne in mind that the latter forms, or those which the evidence of associated animal remains would show to be oolitic, are only found in the upper beds of the Damoodah series, while those which are common to the Australian fields are those chiefly found in the lower beds. Unfortunately, no animal remains whatever have been found with these plants in the districts examined, excepting some annelide tracts useless as distinctive forms. He preferred, under these circumstances, waiting for further evidence before giving any definite opinion as to the age of this widely-extended and important group of rocks. Mr. Oldham then stated that there seemed good reason for separating altogether from the several groups of rocks to which he had referred the whole of the great thickness of sandstones which formed the great Vindhyan range, extending almost entirely across India, from the mouths of the

Nerbudda to the Ganges at Monghyr. These appeared to be of prior date, and there was a probability that there was a great line, or a group of lines, of dislocation passing along the general line of the valley of the Nerbudda, and the effects of which might be traced over a very large area, extending towards the north-east, possibly even into the Valley of Assam. Besides the examination of these districts, which together included an area of more than 30,000 square miles, the Geological Survey had been able to add to the knowledge of the structure of the country in other ways. 1. An excellent selection of fossils from the neighbourhood of Verdachellum in Madras, for which they were indebted to Brooke Cunliffe, Esq., who had been associated with the Rev. Mr. Cay in the first examination of these fossils, had enabled them to add largely to the lists of Forbes, and to establish more conclusively than before the cretaceous age of these deposits. 2. The exertions of Captain Keatinge at Mundlaiser, to whom Mr. Oldham had pointed out the interest of the inquiry, had collected a good set of organic remains from the limestone at Bang, to the west of Mhow, which had enabled him to fix the age of those deposits as contemporary, or nearly so, with the cretaceous beds of Trichinopoly and Verdachellum. This discovery gives rise to many important speculations as to the age of other beds, and also as to the epoch of the elevation of all Central India; but more data were required before these could fairly be entered

upon.

On the Ironstones in the Oolitic District of Yorkshire. By JOHN PHILLIPS,
M.A., LL.D., F.R.S., Reader in Geology in the University of Oxford.

On the Discovery of Paradoxides in New England.
By Professor W. B. ROGERS.

On the Geological Survey of Pennsylvania. By Professor H. D. ROGERS.

On the Fossils of the Dingle District. By J. W. SALTER, F.G.S. In this communication the author gives the detailed succession of beds in a section from Sibyl's Head on the north to Dunquin and Machin Mountain on the south, and shows from the fossil succession, as had also been demonstrated by Mr. G. Du Noyer from sections, that,

1. There is no evidence of a great anticlinal arch, including the whole of the Silurian beds, nor of a double anticlinal divided by the mass of Clogher Head (there is however, a great flexure and fault at this point), but rather the underlying rocks, Silurian and Lower Devonian, taken in a rough sense, lie in a rude, faulted and broken synclinal, the lowest beds being respectively at Sibyl's Head on the north, and at the Bull's Head promontory east of Dingle, on the south.

2. The Wenlock and Ludlow formations are present, each well-developed, and very much like those of Britain, with some differences in the distribution of the fossils. The Chonetes lata, for example, a characteristic Ludlow fossil in Britain, is here most abundant in the lower Wenlock beds. Many common trilobites and shells also occur in it. Great coral beds (chiefly Favosites polymorpha) distinguish the Wenlock series, with abundance of a large Spirifer, S. bijugosus, and of Aviculæ peculiar to the district.

Pentamerus Knightii, Rhynchonella navicula, with several species of corals, mark the upper or Ludlow series; and there is a mass of fucoid-bearing strata-very remarkable and persistent-between the Ludlow and Wenlock series. At Bull's Head promontory, beds with Pentameri occur beneath Wenlock strata; and though these cannot be connected with the beds to the northward, there is reason to think them the equivalents of the beds at Sibyl's Head (which underlie the old red conglomerates), and that they are here brought up by enormous faults.

Lastly, attention is drawn to the fact, that this is the only Upper Silurian district of Ireland; that of Uggool, county Mayo, being rather the uppermost beds of the great Llandovery or May Hill sandstone series, so fully developed in Connemara.