bluuebunny/crossref_metadata_2025 huggingface dataset:
A Note on the Petrology and Physiography of Western Liberia, West Coast of Africa
Authors: Parkinson John
Published: October 2009

I.
Petrology
.

By the kind permission of Sir Harry Johnston, G.C.M.G., I am enabled to make the following brief contribution to the geology of part of Western Liberia. The district described lies to the north and north-east of Monrovia, in Montserrado county, and includes the lower part of the basin of the St. Paul or Ding River. These notes are the result of a seven months' journey in the Republic.

Taking the southern part first, it should be noted that garnetschists and various gneisses, for the most part greatly decomposed, are exposed in the neighbourhood of Whiteplains and along the Caresburg Road. In typical specimens of the former collected near Whiteplains, garnets are abundant, much cracked and very irregular in outline. Flakes of biotite are common, quartz is occasionally plentiful; and the felspar is, at least partly, an acid plagioclase. Phenocrysts are rare. Kyanite-schists are probably associated with these rocks, for the distinguishing mineral is common in the gravels of the streams, but it has not yet been traced to the parent rock.

These garnet-biotite-granulites or schists form a well-marked group, probably distinct from the commoner gneisses with which they are associated. In the latter the occurrence of a monoclinic, and possibly also of a rhombic, pleochroic pyroxene is worthy of note. Quartz is common, and occurs typically in elongated lenticles.

The Whiteplains garnetiferous rocks may be correlated with others petrographically similar, found between Suen and Arthington on the western bank of the St. Paul, and with garnet-graphitegneisses and tremolite-schists
Solution-Valleys in the Glyme Area (Oxfordshire)
Authors: Spicer E. C.
Published: October 2009

In the plateau composed of Great Oolite rocks between the Evenlode and the Cherwell there is a series of remarkable valleys of similar character running in various directions. The area to be briefly considered is triangular: the base is formed by the strike-valley of the Upper Swere running north-eastwards, and by its continuation from the Great Rollright water-parting running south-westwards. The Dorn and the Glyme define an inner triangle in this area (see map, p. 336).

It will be seen that the streams run in many different directions. Reference to a contoured map will show that there are innumerable valleys connected with and opening into the numerous streams draining the area, and that their trend varies. In the main, however, they are either strike-valleys or dip-valleys, though in the field their trend is not so evident. The valleys always begin suddenly upon the plateau, and descend with steep sides along winding courses into the nearest evident stream. The upper part of each valley is always dry. The cross-valleys are usually dry throughout. There are no terraces in the valleys, and there is no drift upon the plateau, nor any alluvium in the streams. The general appearance of the plateau-valleys is not of erosion but subsidence, as if an enormous snake had left a cast upon a yielding surface.

Taking any part of the area, such as that where Grimm's Brook enters the Glyme west of Wootton on the right bank (Pl. XXXVIII, fig. 2), it will be seen that the
On
Metriorhynchus Brachyrhynchus
(Deslong.) from the Oxford Clay near Peterborough
Authors: Leeds E. Thurlow
Published: October 2009

This species of
Metriorhynchus
was first described by E. Eudes-Deslongchamps in 1868 in his ‘Notes Paléontologiques,’ and was based on an imperfect skull obtained from Oxfordian strata in the department of Calvados (Lower Normandy). He was led to distinguish it from other species of Metriorhynchus on account of the shortness of the snout (‘museau’ is the word which he employed, under which term he included every thing in front of the orbits), the principal feature determining the species being found in these bones. In his table of Metriorhynchidæ (
op. cit.
p. 294) he defines it as follows:—

‘Museau très court, pointe des os nasaux atteignant et même dépassant la suture des os intermaxillaires.’

He mentions one other mutilated skull found near Poitiers, and now in the Museum at Paris. Besides this, Prof. Bigot, of the University of Caen, to whom I owe my best thanks for photographs of the type-specimen and for much valuable information, tells me that there is in the Muséum de la Faculté des Sciences at Caen a very mutilated skull with part of the vertebral column, and another fragment of a skull, which may probably be referred to
Metriorhynchus brachyrhynchus
.

Apart from these, I can learn of no other specimens. The species is not mentioned in the ‘Catalogue of Fossil Reptilia in the British Museum’ (Lydekker, 1885) nor in ‘British Fossil Vertebrata’ (Smith Woodward & Sherborn, 1890). Prof. E. Fraas, in his monograph on the Thalattosuchia, among which he includes the Metriorhynchidæ, compares it with
Dacosaurus
On some Fossil Fishes discovered by Prof. Ennes de Souza in the Cretaceous Formation at Ilhéos (State of Bahia), Brazil
Authors: Woodward Arthur Smith
Published: October 2009

The precise extent of the Lower Cretaceous formation on the coast of Bahia (Brazil) still remains undetermined. Last year, Mr. Joseph Mawson gave to the Society an account of the deposits referable to it in the neighbourhood of Bahia itself; through Dr. Orville A. Derby, Prof. Eunes de Souza, of Rio de Janeiro, has now submitted to me some fossil fish-remains from Ilhéos, which prove that it extends at least to that point, 130 miles south of the area previously described. The specimens represent three new species, but two of them are closely related to those from Bahia, and the third appears to belong to a typically Cretaceous form of Clupeoid fish which has not hitherto been found in America. Prof. de Souza has generously presented these fossils the the British Museum (Natural History), where they form an interesting supplement to Mr. Mawson's collection. They are preserved in bituminous shale like that in which most of the fossil fishes occur near Bahia.

A Cœlacanth is represented by the remains of the greater part of a skeleton of a fish about 60 centimetres long, by part of a cranium, and also by a few bones of a smaller head. The ridged ornament on some of the external bones shows that the species belongs to the genus
Mawsonia
, which is only known from Bahia.

The head of the type-specimen is so much crushed, that it is only of interest as showing the characteristic rugose ornament on part of the cranial roof and
The Hornblendic Rocks of Glendalorgh and Greystones (County Wicklow).
Authors: Thomson James Allan
Published: October 2009

1.
Introduction
.

The two occurrences of hornblende-rocks of which this paper treat have been briefly described before, that of Glendalough under the name of amphibolite by Prof. Sollas, that of Greystones as hornblende-picrite by Prof. Watts. Both these authors felt tha there were points of interest about these rocks which required fuller working-out; and when, at Prof. Sollas's suggestion, I commenced the study of the amphibolite, Prof. Watts kindly offered to delay the publication of an interesting communication which he had in hand on the picrite, so as to allow me to give a complete description of both rocks. In recording my thanks I have also to mention Prof. Cole, Mr. Seymour, and Dr. Flett, to whom I am indebted for facilities to examine sections in the Geological-Survey collections and for many fruitful suggestions.

Both these rocks are intrusive into Ordovician strata in the east of County Wicklow. This area has been described in detail in the Geological-Survey Memoir, its igneous rocks are well known from the descriptions by Prof. Watts, and its geological history has been discussed by Prof. Sollas. The outstanding feature is, that into a thick mass of arenaceous and argillaceous sediments and intercalated volcanic rocks of Cambrian and Ordovician age, there was intruded in laccolitic form an immense mass of granite. The intrusion of the Leinster Granite seems to be connected with the Caledonian system of folding: for its outcrop runs in a north-east to south-west direction for some 30 miles, from Killiney to New Ross.
The Bala and Llandovery Rocks of Glyn Ceiriog North Wales.
Authors: Groom Theodore , Lake Philip
Published: October 2009

1.
Introduction
.

It was in continuation of the work which we had begun at Corwen that in 1892 we paid our first visit to Glyn Ceiriog. At Corwen we had been unable to detect any decisive proof of unconformity at the base of the Corwen Grit; but in the Bala Beds below we did not find the characteristic fossils of the Sholeshook Limestone or of other Upper Bala deposits, and were therefore led to believe that the highest beds of the Bala Series were absent, and that there was probably an unconformity which was too slight to be visible in so small an area.

The section at Glyn Ceiriog encouraged the hope that higher Bala Beds might there be found, and it seemed, moreover, to afford excellent opportunities for the examination of the whole Bala Series. To judge from the map of the Geological Survey, or from a cursory inspection of the ground, it would be difficult to imagine a locality more favourably situated for the purpose. The valley of the Ceiriog appears to cut through the whole of the Bala Series, from the lowest ash-band up to the Glyn Grit; and, owing to the steepness of its banks, the rocks are admirably exposed, while most of the beds are fossiliferous almost to excess.

It was not long, however, before we found unexpected difficulties. The same succession, or rather the upper portion of it, should appear in the nearly parallel valleys of Tyn-y-twmpath and Nantyr; but when we examined those
On the Stratigraphy and Structure of the Tarnthal Mass (Tyeol).
Authors: Young Alfred Prentice
Published: October 2009

The Tarnthaler Köpfe are an isolated mountain-mass in the north of the Tuxer Alps. The appended sketch-map (fig. 1), together with the sections (figs. 2 & 3) copied from Pichler and Rothpletz, affords a general idea of the geographical distribution of the rocks of which the mass is composed and the vertical section of their arrangement in the mountain-mass itself.

The stratigraphy of the mass has been very differently interpreted by various investigators. Their views will be found in the papers noticed below.

Adolf Pichler in 1859 supposed the sequence of strata to be normal throughout, the capping mass of serpentine being treated as a sedimentary rock. He enumerates the following fossils, found in a grey limestone in place:—
Belemnites, Pentacrinus, Gervillia inflata, Lithodendron, Rhynchonella
. The whole mass of dolomite, with the calcareous schists above it, is shown in his section, as Lias, in which formation the author includes the Rhætic.

In 1894 Prof. A. Rothpletz announced a further discovery of Rhætic fossils in this locality—
Terebratula gregaria, Modiola minuta
, and several others. The igneous character of the serpentine is recognized; but otherwise the descriptions and sections seem to assume a normal and continuous succession of beds, from the Triassic dolomite below to the youngest ‘Kalk-thon’ and Wetzschiefer above.

In the same year Dr. F. E. Suess published the results of his own studies in this region. The serpentine and quartzite-schists are held to be older than the calcareous schists and dolomites, and it is supposed that they were brought into
The Geological Interpretation of the Earth - Movements associated with the Californian Earthquake of April 18th, 1906
Authors: Oldham Richard Dixon
Published: October 2009

The Californian earthquake of 1906 was accompanied by very considerable displacements of the ground along a great fault-line, which has been traced for a distance of about 200 miles from its southern extremity to the point where it finally passes out under the sea. As several stations of the principal triangulation lay within the disturbed area, the Government of the United States decided to repeat the observations over this area, and determine with accuracy the present positions of the points previously fixed. The result of this work has been issued, with most commendable promptness, as an Appendix to the Report of the Coast & Geodetic Survey for 1907, and the results seem of such importance, from the light thrown on the nature of the earth-movements which gave rise to this earthquake, that I have thought it desirable to make a detailed study of them from the geological point of view.

The area covered by the observations is not co-extensive with, but covers the most important part of, the seismic area; it extends from near Monterey, in the south, to Point Arena, in the north, and within this area all the points fixed by the triangulation which was carried out at various times between 1851 and 1899 were again fixed after the earthquake of 1906.

When the results came to be worked out, it was found that wherever triangulation of earlier date than about 1868 was connected up with triangulation of later date, the positions of the connecting points did not
On the Fossil Plants of the Waldershare and Fredville Series of the Kent Coalfield
Authors: Arber E. A. Newell
Published: October 2009

At the present time, important series of coal-seams have been proved by means of borings in three localities in South-Eastern Kent. As apparently the lithological sequence, including the coal-seams, is quite distinct in each case, we may, as a temporary expedient until the structure of this concealed coalfield can be demonstrated, distinguish them as the Dover, Waldershare, and Fredville Series.

The Dover Series was the first discovered. In 1886, a boring was made at the site of the proposed Channel Tunnel on the foreshore at Shakespeare Cliff, rather more than a mile to the west of the Admiralty pier at Dover. The Coal-Measures were reached in 1890, at a depth of 1100 feet, and the boring subsequently penetrated to a depth of about 2270 feet, passing through thirteen seams of coal, varying from 1 to 4 feet in thickness. The Dover Series is essentially a thin-coal series, and sandstone-beds are comparatively numerous. For many years past attempts have been made to sink shafts, and to work the coals, on or near the site of the original borings, by the Kent Collieries, Limited, but hitherto with small success owing to difficulties in connexion with the inflowing water derived from the Mesozoic rocks. The fossil plants obtained from the original boring through the Dover Series were described by Prof. Zeiller in 1892, and will be further discussed here.

in 1904, a new company, the Kent Coal Concessions, Limited, with which several daughter companies and syndicates have more recently been associated, was formed
The Relations of the Nubian Sandstone and the Crystalline Rocks south of the Oasis of Kharga (Egypt)
Authors: Beadnell H. J. Llewellyn
Published: October 2009

In the geological study of a country there is nothing of more importance than the mutual relations of the different rock-groups of which it is made up, and yet in Egypt it is perhaps more especially in regard to those relationships that our views have had from time to time to be materially altered. In particular, I may instance the relationships of the Eocene and Cretaceous Systems in different parts of the country, notably at Abu Roâsh, in the Eastern Desert, and in the Oases. The object of the present paper is to raise the question of the relation of the granites and associated crystalline rocks to the overlying sedimentary formations, a relationship of fundamental importance, and to put on record some observations bearing on the subject made during a brief examination of the country to the south of the Oasis of Kharga, undertaken with the primary object of eliciting certain information regarding the water-supply of that oasis. These observations appear to me to afford strong evidence that in this district the granites, in their present position at least, are younger than the overlying members of the Cretaceous Series.

The Crystalline Rocks south of the Oasis of Kharga.

That a solitary exposure of igneous rock exists at Jebel Abu Bayan, in the Libyan Desert south of the Oasis of Kharga, has long been known. Capt. Lyons, with reference to this locality, wrote :

‘The rock is a coarse-grained hornbleudic granite, with large crystals of pink orthoelase, and is apparently identical
On Labradorite - Norite with Porphyritic Labradorite Crystals: a Contribution to the Study of the Gabbroidal Eutectic
Authors: Vogt Johan H. L.
Published: October 2009

The object of this paper is to contribute to the investigation, on a physico-chemical basis, of the sequence of crystallization in the gabbroidal eruptives.

The Lofoten and Vesteraal Islands on the northern coast of Norway (lat. 67° 50′ to 69° N.) constitute, as is well known, a petrographical province with a very considerable number of eruptives, among which orthoclase-plagioclase-rocks, especially monzonite and banatite, are the most frequent.

On one of the islands, Flakstadö, there is an area of labradorite-rock comparatively poor in ferromagnesian silicates and magnetite, besides labradorite-norite with somewhat larger quantities of the same. Under the name ‘labradorite-norite’ is denoted a rock which lies chemically and mineralogically on the boundary between labradorite-rock and norite.

The field-exposure of the labradorite-rock with the labradorite-norite has a length of sisteen and a half kilometres, a breadth averaging from two and a half to three and a half kilometres, and an area of about 50 square kilometres. To this must be added its continuation under the sea. At the northern margin, towards the Archæan in the neighbourhood of Napp Farm on Flakstadö, the labradorite-norite occurs with a porphyritic development, that is, with phenocrysts of labradorite-felspar, often of remarkably large dimensions. We will now examine this latter rock more closely.

The porphyritic labradorite-norite of Napp, like most of the rocks belonging to the eruptive province in question, generally shows little or no sign of pressure. It is in most places coarsely crystalline, with labradorite-phenocrysts measuring as much as 15 or 18 centimetres in length and from 6 to 8 in breadth. It has
On the Igneous and Associated Sedimentary Rocks of the Tourmakeady District, County Mayo
Authors: Gardiner Charles Irving , Reynolds Sidney Hugh
Published: October 2009

Our
object in the present paper is to describe a series of igneous rocks associated with beds containing Ordovician fossils, and occupying a tract of country, having a width of about a mile, which extends along the western shore of Lough Mask from the hamlet of Derrindaffderg in the north to the neighbourhood of Tourmakeady in the south, a distance of about four and a half miles.

At the southern end of the area, on its eastern side, this igneous series of rocks is bounded by massive conglomerates; and rocks lithblogically similar, though probably of much later date, form the whole of the western boundary. Along most of the eastern border occur conglomerates and sandstones, to which we, following the Survey, shall refer as the basal beds of the Carboniferous, although they may be regarded with equal probability as representing the 01d Red Sandstone.

The surface is undulating, but the physical features are not striking—the ground never rising, in the area with which we deal, to a greater height than about 400 feet, or some 350 feet above Lough Mask. A number of streams traverse the district from west to east, and afford an excellent series of sections ; but, apart from these, exposures are almost everywhere numerous, this being partly due to the fact that the district is free from drift.

Considering the interesting and varied character of its geology, it is remarkable that comparatively little has hitherto been written about this area. In 1874, G. H. Kinahan,' in a paper
[On the Fauna of the Tourmakeady Rocks]
Authors: Reed F.R. Cowper
Published: October 2009

A. General Remarks on the Fauna.

(1) The Limestone (Tourmakeady Beds).—The fauna of the limestone is not rich in species, but the fragmentary nature of the organic remains is the main obstacle to a satisfactory knowledge of its characteristics. Members of the genus
Illœnus
seem to be the most abundant fossils. In spite of the matrix and mode of preservation of the fossils resembling those of the Chair of Kildare and Keisley, the facies of the fauna must be regarded as indicating a considerably lower horizon, for not only are the typical species of the Upper Bala l absent, but the assemblage is not that of the Middle Bala, and certain genera and representative species which occur m it are outv known elsewhere from beds correlated with the Lower Bala (Llal{deilo). Of such fossils we may especially note the species of
Pliomera
and
Porambonites
. The genus
Pliomera
occurs abroad only in the lower part of the Ordovician— on horizons generally regarded as homotaxial with the Arenig and Lower Bala. Such is the case in Scandinavia, the Baltic provinces of Russia, and North America, while in Scotland and Ireland it is found only in the Craighead (Stinchar) Limestone and in the Tramore Limestones respectively, which are believed to lie considerably below the Middle Bala. No undoubted representative of the genus from beds of later age than Lower Bala is definitely known. The same remarks apply to the genus
Porambonites
, which is especially characteristic of the lower stages of the Ordovician in the Baltic region. The evidence
Note on some Geological Features observable at the Carpalla China-Clay Pit in the Parish of St. Stephen's, Cornwall
Authors: Collins Joseph Henry
Published: October 2009

This clay-work is situated on the Burngullow branch of the Great Western Railway, about a mile and a half north-west of Burngullow Station, at an elevation of about 550 feet above sea-level.

The land slopes generally from the east towards a rather deep valley, the railway running from nearly south to north along the eastern edge of the valley, on a low embankment across two fields where the inclination is very gentle. About the middle of its length, the embankment is traversed from east to west by an accommodation-road, over which the line is carried by an arch of masonry. East of the railway and also on the southern portion of the west side, the ground has been very thoroughly explored by means of pits and shafts, while the northern portion of the west side is fully exposed by the great clay-excavation (the Carpalla clay-pit), now over 100 feet deep.

The surface-soil or ‘ meat-earth,’ generally almost black and of a peaty character, covers or has covered the whole estate to a depth of 6 inches or more. Beneath this is everywhere a ‘ growan’ 1 or stratum of subsoil, varying in depth from 2 up to 10 or 12 feet. On each side of the railway from the hedge marked NN on the accompanying plan (fig. 1, p. 156), as far as the accommodation-road above mentioned, this growan rests upon a stratified rock locally known as killas, which is here really a well-marked tourmaline-schist ; beyond the road, it
The Relation of the Ordovician and Silurian Rocks of Conway, North Wales
Authors: Elles Gertrude L.
Published: October 2009

The area constituting the Conway District, for the present purpose, extends from the mountains of Penmaenbach and Dinas on the west, southwards as far as DerwendJg, and thence eastwards to the Conway River, thus including Conway Mountain, and the whole of the country lying immediately north, south-west, and south of the town of Conway itself. On the east side of the estuary there is also the area lying east, north-east, and south-east of the village of Deganwy.

The region has not hitherto been worked in any detail, wherefore the literature as a whole is scanty and the information somewhat unsatisfactory. The volcanic rocks have received the greatest share of attention, some of the rhyolites, and especially the nodular rhyolites, having been described by Prof. Bonney, Mr. Harker, Prof. Grenville Cole, and others; but the sedimentary rocks have rarely received more than a general notice.

The more important papers referring to the district are the following :—

(A) Stratigraphical.

Jukes, in his ‘ Letters,’ makes several references to the district; of these the most important statement seems to be that where he refers to Conway Castle as standing ‘on the very top of the Bala Beds, somewhere about where the Hirnant Limestone ought to be.’

Unfortunately, he afterwards accepted the view that the rock in question was the equivalent of the Bala Limestone. 1 In the light of recent work, his earlier opinion would seem to be more correct.

Prof. Lapworth, in his classical work on the ' Geological Distribution of
On the Sculptures of the Chalk Downs in Kent, Surrey, and Sussex
Authors: Clinch George
Published: October 2009

The Author classifies the various forms of sculpture of the Chalk Downs under three heads, namely, (1) dry valleys of simple form, (2) dry valleys of complex form, and (3) wet valleys. He draws attention to the relatively small catchment-areas of the dry valleys, and to the large number of tributary valleys found in some districts, two points which he considers have not hitherto received entirely satisfactory explanation.

While accepting the view that frozen conditions in former times altered the drainage-system of the Chalk, he argues that the most potent excavating force was the frost itself, acting on Chalk saturated or highly charged with water. He points out the following peculiarities of dry Chalk valleys:—(1) the great size and breadth of the valleys in relation to their catchment-basins; (2) the ramifications of some of the valley-systems; and (3) the termination of many dry valleys just short of the crest of the Chalk Downs.

In order to account for these phenomena, the Author propounds the following theories:—

(1)

The chief part of the valley, during and after periods of low temperature, being occupied by a mass of ice, erosion of the Chalk would naturally be more active at the sides than in the bottom of the valley: lateral development and sometimes elaborate ramification being the result.

(2)

The diminution of the catchment-area, due to the cuttingback of the valley towards the highest level, would have the effect of removing one of the chief agents in the breaking-up of the Chalk, with the result that the valley would die out just short of the crest of the Chalk Downs.
A Contribution to the Petrography of the New Red Sandstone in the West of England
Authors: Thomas Herbert Henry
Published: October 2009

I. Introduction.

In a former paper communicated to this Society I dealt with the mineralogical constitution of the great Pebble-Bed, as developed in Devon and Somerset. The results obtained encouraged me to undertake a similar study of the other members of the New Red Sandstone Series in that district ; and, in the following communication, I have endeavoured to point out the mineralogical and physical differences exhibited by the microscopic particles which form the finer portions of the deposits. The classification and subdivision of the New Red Sandstone Series in Devon and Somerset has gradually evolved from the labours of several geologists, and I propose to use those subdivisions which are now adopted by the Geological Survey.

The New Red Sandstone in the area under consideration may be divided as follows, commencing with the older beds :—

These subdivisions are founded solely on lithological characters, and therefore form the most natural basis for a petrographical study.

The Lower Breccias are well-developed, and have been examined on the south coast at Teignmouth and Dawlish, along the western side of the Exe estuary on the flanks of the Haldon Hills, in the Exeter district, and in the Crediton and Stogumber valleys. They usually consist of deep-red breccias, sands, and sandstones, most often loose and incoherent, but occasionally compacted into rocks of more solid character.

The Lower Sandstones, which for the most part occupy a position above the breecias, have been studied on each side of the Exe estuary, in the vale of
On the Boulders of the Cambridge Drift: their Distribution and Origin
Authors: Rastall Robert Heron , Romanes James
Published: October 2009

I. Introduction.

The origin and distribution of the boulders of the Glacial Drift of Cambridgeshire and the adjoining countries is a subject of great interest on which hitherto little work has been done. Although much has been written on the Glacial deposits of this district as a whole, little attempt has been made to examine in detail the types of rock represented in the Boulder-Clay and to trace them to their sources. During the last seven or eight years a large amount of material has been collected, both by the members of the Sedgwick Club and by other independent workers. A brief account of some of the results obtained up to that time was given by Mr. Fearnsides in the official hand-book compiled for the Cambridge meeting of the British Association in 1904, and a short paper entitled ‘On Boulders from the Cambridge Drift, collected by the Sedgwick Club’ was published in the same year by one of the present authors. Since that date much new material has been collected, and the whole has now come into our hands. The additional evidence thus made available, shows that the conclusions set tbrth in the previous publications can be considerably extended.

The total number of boulders collected now amounts to many hundreds ; and, as naturally would be expected, a great number of them, perhaps the majority, are of uncertain origin, since it, is clear that the field of derivation is a very wide one. However, a large number of rock-types have
On Overthrusts at Tintagel, North Cornwall
Authors: Dewey Henry
Published: October 2009

I. Introduction.

On mapping the country to the north of Bodmin Moor for the Geological Survey, it was found that the slate-rocks, as noted by Mr. John Parkinson, are separable into several well-marked lithological types. These types are of widespread occurrence, and strike across the country in parallel zones in a general west-north-westerly and east-south-easterly direction with a constant dip to the north-north-east.

But, although this stratigraphical succession occurs over so wide an area, it apparently broke down in the Tintagel district, where a repetition of the strata was found near the coast. Subsequent investigation, however, proved the repetition to be due to overthrusts from the west-north-west. With the district affected by overthrusts I propose to deal in the present paper.

Several observers have written about the geology of Tintagel, but as none of them interpreted the structure, it, is only ,ecessary to give references to their papers in the following list :—

II. Description of the Area covered by the Map (Pl. XIII).

The area represented on the map covers about 5 square miles, with about 4 miles of coast-line. The district forms a plateau ending off in cliffs which are between 300 and 400 feet high. A portion of a still higher plateau rising to 600 feet occurs in the south-eastern corner of the map. Two small streams dissect the lower plateau, the one on the north forming the Rocky Valley ; and the other, on the west, the Trevena Valley. The whole area forms a land-mass which
Glacial Erosion in North Wales
Authors: Davis William Morris
Published: October 2009

I. The Form of Snowdon.

An excursion around Snowdon, the highest of the Welsh mountains, in September, 1907, led me to the conclusion that a large-featured, round-shouldered, full-bodied mountain of pre-Glaeial time had been converted by erosion during the Glacial Period—and chiefly by glacial erosion—into the sharp-featured, hollow-chested, narrow spurred mountain of to-day. Or, to phrase it in somewhat more technical style, that a body of ancient slates, felsites, and volcanic ashes, greatly deformed in Palæozoic time and greatly worn down in successive cycles of Palæozoic, Mesozoic and Tertiary erosion, was reduced before the Glacial Period began to subdued mountain-form with dome-like central summit, large rounded spurs, and smooth waste-covered slopes, and with mature valleys drained by steady flowing streams which branched delicately headwards, with steepening slope, and which joined each other mouthwards in the accordant fashion that so systematically characterizes the drainage of all normally subdued mountain-masses. Also that this full-bodied mass was transformed during the Glacial Period, chiefly by the glacial excavation of valley-head cwms and by the glacial widening and deepening of the valleys themselves, irate a sharp central peak, which gives forth acutely serrated ridges between wide amlphi theatres: the serrated ridges changing into broad-spreading spurs as they are followed outwards ; the wide amphitheatres, backed by high rocky cliffs, opening by great rock-steps to irregularly deepened trough-like valleys, with oversteepened, undissected sides, sometimes smooth, sometimes of a peculiarly roughened slope; the smaller lateral valleys hanging in strikingly discordant fashion over the floors of the larger
The Nephrite and Magnesian Rocks of the South Island of New Zealand
Authors: Finlayson Alexander Moncrieff
Published: October 2009

Ever since Hochstetter's work on the olivine-rock of the Dun Mountain, and on the New Zealand nephrite or ‘greenstone,’ the rocks of the ‘magnesian belt’ of the South Island of New Zealand have had an absorbing interest for students of that district. The term ‘magnesian belt’ is here used to denote those peridotites and serpentines that have hitherto been frequently referred to by the names ‘serpentine-belt’ and ‘mineral-belt,’ Until recent years, however, the occurrence and nature of the various exposures which comprise this most interesting and significant petrographic province have remained rather obscure, owing to the rugged nature of the country and the inaccessibility of the chief localities.

In this paper is given a general account of the peridotite- and serpentine-rocks of the South Island and a discussion of the nature and origin of New Zealand nephrite. Those analyses which are not attributed to others are my own work, and were made in the geological laboratory of the Imperial College of Science & Technology, South Kensington.

II. The Peridotites and Serpentines.

General Occurence and Relations.

Occurrence.—The position of the known outcrops is indicated on the map accompanying this paper (fig. 1, p. 352). The magnesian belt, as generally understood, first appears as a group of serpeatines and peridotites extending from D'Urville Island in a south-westerly direction for some miles past the town of Nelson. Serpentines have also been observed in the Buller basin ; and still farther south, in the western foothills of the Southern Alps, occur the disconnected sills
Some Notes on the Neighbourhood of the Victoria Falls (Rhodesia)
Authors: Codrington Thomas
Published: October 2009

A stay of nearly four months at Government House, Livingstone, in 1908, afforded me the opportunity of making observations at leisure and gathering the information which is embodied in the following paper.

Livingstone, now the seat of the Administration of North-Western Rhodesia, is within easy reach of the Zambesi at the boathouse 2½ miles above the Victoria Falls. From that point all parts of the river are accessible as far as the rapids, 5 miles farther up, and downwards nearly to the Falls, which can also be reached by railway. Much time was passed on the river, and every facility was afforded me for visiting both sides of the Zambesi for some miles above and below the Falls, and for seeing the valley of the Maramba for some 6 miles upwards from its confluence with the Zambesi. I had the advantage of Mr. G. W. Lamplugh's recent papers on the Geology of the Zambesi Basin, and on the Occurrence of Stone-Implements around the Victoria Falls, and also of access to maps, plans, levels, etc., prepared by the engineers of the British South Africa Company, to whom, and many others, my thanks are due for help and information.

In bringing forward these observations, it is not necessary to refer to what has previously been written, as the literature has been recapitulated as lately as 1907 in Mr. Lamplugh's paper above mentioned. With what is said in that paper about the gorge below the Falls I entirely agree, and to it I
On the Karroo System in Northern Rhodesia, and its Relation to the General Geology
Authors: Molyneux Arthur John Charles
Published: October 2009

In 1903 (in vol. lix of this Journal) I described the occurrence in Southern Rhodesia of deposits of Permo-Carboniferous age that have since been correlated with the Karroo System of South Africa. In the present communication will be traced their extension into Northern Rhodesia. There they are found occupying the lowlands of the Zambesi basin, and they also constitute the floors of the trench-like valleys of the Lusenfwa River (or Luano plains), of the Lukasashi River, and probably of the Luangwa. These depressions form a more or less continuous succession of troughs bisecting Rhodesia diagonally, along a distance of some 800 miles, that is, from the Deka River to the head of the Luangwa. They lie some 2000 feet below the surrounding country, which is of plateau type and is made up of metamorphic and crystalline rocks of the pre-Karroo complex. The change from upland to valleyplains is generally abrupt, giving rise to steep escarpments that appear as mountains when viewed from the lower position.

Nowhere, so far, in the vicinity of these depressions have ‘highlevel’ areas of Karroo rocks been met with on the plateau, and one's first impression is that these basins are vestiges or' an original landscape, in which the sediments were deposited. But we have been prepared by :Mr. G. W. Lamplugh, in his description of the Deka Fault, for great displacements of Karroo strata and earthmovements, and there is ample evidence to show that these valleys and low-lying regions of sediments are largely due to
On the Anatomy of Lepidophloios laricinus, Sternb
Authors: Watson D. M. S.
Published: October 2009

A Specimen of
Lepidophloios
laricinus
, found in one of the coal balls of Lancashire, shows the internal structure. The species is new, and is of the ordinary lepidodendroid type, but is remarkable for the great size aad strength of the corona and the leaf-traces.

Lepidophloios
acadianus
, Dawson, which is identical with
L
.
laricinus
, appears to differ iu its internal structure, in having still stronger protoxyleul-points and leaf-traces.

Lematophloios
crassicaule
, Corda, which is
L
.
acerosus
, L. & H., appears to resemble greatly tile Lancashire specimen of
L
.
laricinus
in its structure, and is quite distinct from the specimen of the same form described by Cash & Lomax.

Lepidodendron
fuliginosuem
, Will., a structural species, appears to include a specimen the external structure of which corresponds with
Lepidophloios
acerosus
,
Lepidodendron
obovatum
,
L
.
aculeatum
, and
Sigillaria
discophora
.

Under these circumstances, it, is proposed to take no account of the impression-species in considering the synonymy of the structural specimens, and
vice
versa
. When the exterior of a structural specimeu is actually known, it may be referred to by the name of the structural species, with that of the impression-species added in brackets.
The Pitting of Flint-Surfaces
Authors: Carus-Wilson Cecil
Published: October 2009

Regular pittings of uniform size are occasionally seen on flints which have been exposed to the weather. They have been referred to by various authors, but no satisfactory explanation of their origin has been given. The Author procured some interesting examples occurring in a recent deposit near Folkestone. This deposit is formed of materials which appear to have been washed down from the adjacent Chalk hills. The flints appear to have been derived from the sandpipes in the Chalk: their surfaces are much decomposed. The removal of the colloid silica has rendered them very porous, and they absorb a good deal of water. It is believed that the pittings are due to mechanical action. Observations and experiments carried out by the Author indicate that such markings cannot have been produced by blows, nor by any process of desiccation, and that the freezing of the absorbed water seems to be the only satisfactory explanation to account for the various details of the phenomenon.
The Cauldron-Subsidence of Glen Coe, and the Associated Igneous Phenomena
Authors: Clough Charles Thomas , Maufe Herbert Brantwood , Bailey Edward Battersby
Published: October 2009

During Lower Old Red Sandstone times the district of Glen Coe furnished an arena wherein terrestrial disturbance and igneous activity combined to produce effects of imposing magnitude and, as we believe, of some theoretical importance. The paper now presented embodies an account of a cauldron-subsidence which affected an area roughly oval in shape, and measuring not less than 5 miles from side to side. We show that the subsidence took place in at least two stages, and that it was accompanied in a complementary fashion by the uprise of a series of marginal intrusions.

In the first instance the nature of the volcanic succession in Glen Coe will be dealt with, its variations from point to point will be described, and evidence will be adduced to illustrate the marked inequalities of the floor of Highland Schists upon which these volcanic rocks accumulated. The second portion of the paper is devoted to the evidences of the cauldron-subsidence, and treats in some detail of its tectonic features and the accompanying plutonic intrusions. In a final section we have added a theoretical discussion of our results.
On some small Trilobites from the Cambrian Rocks of Comley (Shropshire)
Authors: Cobbold Edgar Sterling
Published: October 2009

T
he
trilobites described in this paper were mainly collected during the progress of the excavations at Comley, which formed one of the subjects of the Report of the Geological Excavations Committee of the British Association, read at the Dublin Meeting, 1908.

The majority of the specimens were derived from the preliminary excavation in the fields, some 200 yards south of the well-known Comley Quarry. This excavation cuts transversely through the same set of beds as those that are worked in the quarry, and, though of only a very shallow depth, it exhibits the most complete section as yet exposed of the local junction between the
Olenellus
and
Paradoxides
divisions of the Cambrian. Between the
Olenellus
Limestone, which in the quarry yields
Olenellus (Holmia) callavei
, Lapw., and the Conglomeratic Grit, which in the same quarry yields
Paradoxides groomii
, Lapw., there is intercalated some 4 feet of grey limestone. Provisionally, I divide this into the following bands, in descending order

I hesitate to assign any definite numbers or letters to these beds, until more is known as to their faunal characteristics, which will throw light on their natural grouping. All these limestones above the
Olenellus
Limestone contain black nodules of, probably, phosphatic matter.

The trilobites occur as aggregations of many parts or fragments of parts, indiscriminately mixed three or four species together, and usually preserve their original form aud convexity. In most cases the test has also been preserved, either wholly or in part; and where this has been the case I
The Skiddaw Granite and its Metamorphism
Authors: Rastall R. H.
Published: October 2009

I. I
ntroduction
.

T
he
main object of this paper is the investigation of the alteration of the sedimentary rocks of the Skiddavian Series by the intrusion of the mass of igneous rock which is commonly known as the Skiddaw granite. One or two cognate subjects will be touched upon, such as the composition and petrographical character of the intrusion, and the general structure and tectonic relations of the sedimentary series; but, in the main, the paper is a study in metamorphism. The Skiddavian Series includes rocks of varying lithological character, grits, flags, shales, and slates, so that the products of metamorphism are not by any means uniform in character; and, in addition to this, the problem is complicated by the occurrence throughout the area of a varying though generally high degree of folding and cleavage. Hence it is necessary to study the effects of thermal metamorphism superposed upon those of a previous dynamic metamorphism.

During my examination of the Buttermere and Ennerdale granophyre, I was naturally led to study the effects of this intrusion on the surrounding rocks, which are well-marked. This subject proved to be an unusually difficult one and I then turned my attention to the metamorphism of the Skiddaw intrusion, in the hope that this would throw some light on the puzzling phenomena presented in the former case. It seemed advisable, therefore, to make a complete study of the Skiddaw metamorphism; and since this latter is in itself the more important case, and probably the more instructive from
Palæontological Notes [on Ordovician Fossils from the Glensaul District]
Authors: Reed Frederick Richard Cowper
Published: October 2009

The fossils from this district which have been submitted to me for determination are mostly poor and fragmentary. They occur in two main types of rocks: namely (i) a hard, coarsely crystalline, reddish limestone (97, 155), and (ii) a rotten, gritty, calcareous ash (62). The specimens from the limestones marked 97 & 155 apparently belong to the same horizon and come from the same bed at different localities, for the rocks are lithologically identical and the faunas are indistinguishable. This horizon may be unhesitatingly correlated with the limestone of the Tourmakeady Beds described on a previous occasion. The more abundant material and newly discovered members of the fauna from these Glensaul localities necessitate a slight revision of my views as to the age of the limestone, and the additional evidence now available points to a somewhat lower horizon than was previously considered to be indicated. In fact, it appears that we must now correlate it with the Scandinavian equivalent of the English Arenig, that is, with the main mass of the
Orthoceras
Limestone. My previous reluctance to place the beds so low was due to the insufficiency of the evidence derived from the fossils; but now there does not appear to exist sufficient ground for refusing to admit that the sediment accumulating here in Arenig times was temporarily of a calcareous nature, and that the fauna which flourished during that interval in the West of Ireland was closely similar to that of the Scandinavian seas, where identical physical conditions of
Problems of Ore-Deposition in the Lead and Zinc Veins of Great Britain
Authors: Finlayson Alexander Moncrieff
Published: October 2009

I. I
ntroduction
.

T
he
lead and zinc districts of Great Britain afford good opportunities for the study of these ores, owing to the variety of types met with and the advanced state of mining. Unfortunately, however, many interesting districts have been exhausted and abandoned, with the inevitable loss of much valuable information, which was not secured when the mines were in operation. As Franz Posepny has truly remarked, ‘Mining, indeed, constantly furnishes fresh evidences in new openings, but it destroys the old at the same time; and if these are not preserved for science before it is too late, they are lost for ever.’

The Geological Survey memoirs, however, have in some cases preserved many data which could not otherwise be obtained. The present work has been carried out on the basis of personal field-work in all the chief districts, coupled with laboratory work at the Imperial College of Science and Technology, where all the analyses tabulated in this paper were made.

The lead and zinc veins of Britain are chiefly of the spathic and barytic types of Freiberg mineralogists. Calcite is the predominant gangue, while fluorspar, barytes, and quartz are also abundant. Zeolites occur locally, as at Strontian in Argyllshire, and at Glendalough (Wicklow). The galena is argentiferous to a varying degree, and rich silver-ores have been mined at Hilderston (Linlithgowshire), at Alva (Stirlingshire), and in parts of Cornwall. These veins, though small and unimportant, are of the Joachimsthal and Annaberg type. The country-rock of the veins embraces nearly all