bluuebunny/crossref_metadata_2025 huggingface dataset:
The Norite of Sierra Leone
Authors: Dixey Frank
Published: October 2009

I. Introduction.

The norite of Freetown (Sierra Leone) was briefly described by G. Gürich in 1887, and in 1918 Prof. S. J. Shand translated Gürich's work, adding a few notes. I had the opportunity of making a detailed examination of this norite, as part of an investigation into the mineral resources of Sierra Leone; and in the course of this work it was found that the norite exposed around Freetown was only one end of a huge noritic complex which made up the whole mountain-mass of the Colony. Moreover, during the examination several features of considerable interest were observed, including the assimilation of one phase of the norite by another, the well-developed banding in the norite, the segregation of the iron-ores, and the sequence of the minor intrusions. These features, together with an important series of intergrowths of the common minerals, will be described in the course of this paper. The investigation into the mineral resources of the Colony, with especial reference to the iron-ores, formed part of the work of the Geological Survey of Sierra Leone during the latter part of 1918 and during 1919.

(2) Physiography of the Area.
2

The Colony is a mountainous peninsula adjacent to the undulating low ground which forms the southern part of the Protectorate. Its mountains rise steeply from a narrow coastal plain to a height of nearly 3000 feet; this plain is continuous with that of the mainland, and is due to a Pleistocene uplift of a little over 300 feet. It
The Nature and Origin of the Pliocene Deposits of the County of Cornwall, and their Bearing on the Pliocene Geography of the South-West of England
Authors: Milner Henry Brewer
Published: October 2009

I. Introduction.

The present paper deals more particularly with the petrography of the younger Tertiary deposits of Western Cornwall which, by reason of their mode of occurrence and lithological similarity to the well-known fossiliferous beds of St. Erth, have been generally assigned to the Pliocene age. These deposits occur as isolated patches of detrital material resting in eroded hollows in Palæozoic or older rocks in the south-western part of the county, and are located at St. Agnes, 4 miles due south-west of Perranporth; at St. Erth and Canons Town in the Hayle-River valley; at Crousa Common, a mile and a half south-west of St. Keverne (Lizard district); and at Polcrebo, near Crowan, 4 miles south of Camborne, where an outcrop of gravels of alleged Pliocene age is found. With the exception of the St. Erth Beds, no fossils have hitherto been discovered in these deposits, and their stratigraphical position has been inferred entirely from general geological and topographical considerations.

The object of this paper is not only to establish the relative ages of these deposits by petrographic methods, but to demonstrate the importance of this mode of attack in problems of stratigraphical correlation where palæontological evidence is in some cases lacking. In addition, the mineralogical factors concerned are used as a guide to the determination of the origin of these sediments and, in conjunction with topographic data, to restore the geography of this part of Britain in early Pliocene times, in so far as the evidence at our disposal allows.
Jurassic Chronology: II—Preliminary Studies. Certain Jurassic Strata near Eypesmouth (Dorset); the Junction-Bed of Watton Cliff and Associated Rocks
Authors: Buckman S. S.
Published: October 2009

I. Introduction.

This paper is to a certain extent a supplement to the communication on ‘Certain Jurassic Strata of South Dorset’ published by the Geological Society in 1910, in so far as it contains a study of another exposure of the Junction-Bed (Domerian, Whitbian, Yeovilian)
1
discovered farther east along the coast; but it also gives a sketch of other Jurassic strata, the sequence of which should be of some importance in connexion with the chronology of the Oolite rocks.

About three-quarters of a mile east of Thorncombe Beacon is Eypesmouth, a break in the cliffs where the little stream, the Eype (pronounced ‘Eep,’ to rhyme with sheep) runs into the sea. East of Eypesmouth is a lofty cliff of about a mile extending to West Bay—the harbour of Bridport.

The cliff is interesting geologically for three considerable faults: one, seen best about a quarter of a mile east of Eypesmouth is a fault of about 500 feet, bringing down Forest-Marble Beds to about the level of Yeovilian strata (
Dumortieria
hemera); another, about the same distance west of West Bay, brings down beds of Fullers' Earth almost vertically—it is a fault of about 120 feet; the third, immediately west of West Bay, shows Yeovilian strata of
Dumortieria
hemera or later—they are later than those on the west of the cliff—lying level with lower beds of Fuller's Earth: a drop as regards the latter of about 150 feet. So the middle and main portion of the cliff is let down by these
Petrology of the Shales-with-‘Beef’
Authors: Richardson William Alfred
Published: October 2009

(A) Laminated Shales

Shales, which are minutely laminated at the outcrop, but appear massive when traced inwards, have been described in Part I (p. 53). The change is accompanied by progressive bleaching towards the weathered surface, and by the deposition of minute, platy crystals of selenite between the laminæ. This bleaching suggests that the development of lamination has been accompanied by a loss of certain constituents of the shales, such as carbon (or hydrocarbons), and also (as indicated by the appearance of gypsum of iron-sulphide. Thus the weathering of the shales has produced a diminution of volume, and the resulting contraction, by separating the individual laminæ, has revealed the minute internal structure of the shales.

It may be noted that similar development of lamination may be seen, for example, in the Rhætic Black Shales at Beacon Hill, Newark.

In bed 71
e
, consisting of well-stratified blue shale, Dr. Lang has found thin biconvex discs of a mineral determined by Mr. W. Campbell Smith as barytes. These discs are irregularly distributed along bedding-surfaces, from which they are readily detached, leaving behind a perfect impression of their shape and markings. The general appearance of these barytes discs can be gathered from fig. 3. The largest specimen examined had a mean diameter of 15 mm., a maximum thickness of 2 mm., and the specific gravity = 4·58. Both the upper and lower surfaces of the discs are marked by radial furrows, very distinct at the thin edge, but faint and often absent in
On the Geological Importance of the Primitive Reptilian Fauna in the Uppermost Cretaceous of Hungary; with a Description of a New Tortoise (
Kallokibotion
)
Authors: Nopcsa Francis
Published: October 2009

In Eastern Hungary the Upper Cretaceous can be divided into two horizons with an unconformity between them (53, 66). The lowest deposits in some places, as near Szászcsor (53), are red conglomerates; in other places (as, for example, Ohaba Ponor) they are red laterites filling fissures in the Tithonian limestone (28). Then follow, extending farther than the red deposits, grey marls and sandstones containing at their base seams of coal (28), and somewhat higher up several ammonites, such as:

Acanthoceras newboldi
Kossmat.

A. cenomanense
Pictet.

A. harpax
Stoliczka.

A. rhotomagense
(Defrance).

Acanthoceras mantelli
(Sowerby).

A. morpheus
Stoliczka.

Puzosia planulata
(Sowerby).

Crioceras
sp. (53).

These help to fix the age of the marls as Cenomanian. Overlying the ammonitiferous strata are coarser sandstones, crammed with enormous numbers of
Actæonella
sp. (28, 53); then come marls and sandstones containing some rare examples of
Actaeonella gigantea
(53), attaining a diameter of 6 inches and more; and lastly, a great complex of rough blue and white sandstones is met with (7), corresponding to the Emscher Sandstone of German geologists or to the zone of
Micraster cor-anguinum
in England. These strata are characterized throughout Transylvania by remarkably large
Inocerami
(53, 65). In
Inoceramus giganteus
Pálfy, for example, each valve attained a length of nearly 2 feet (65).

Unconformably upon these beds rest younger marine layers containing
Pachydiscus neubergicus
Hauer,
P. colligatus
Binck,
Scaphites constrictus
Sowerby (53), and numerous bivalves and gasteropods (51, 64), among which it is sufficient to mention
Melanopsis galloprovincialis
Matheron and
Pyrgulifera pichleri
The Petrology of the Metamorphosed Rocks of the Start Area (South Devon)
Authors: Tilley Cecil Edgar
Published: October 2009

The narrow strip of country forming the southernmost peninsula of South Devon, and extending from Start Point westwards to Bolt Tail, has been the subject of repeated enquiry by various geologists since the first report on the geology of Devon by Sedgwick & Murchison.

On the north this area is bounded by rocks the Devonian age of which is attested by definite organic remains. Whether the rocks of the Start peninsula themselves are also of this age, or whether an older group, has been much discussed, and no small part of the literature is devoted to this subject, apart from any exhaustive study of the rocks themselves. Prof. T. G-. Bonney1 appears to have been the first to apply microscopic petrographic methods to the elucidation of the rocks themselves, and, following him, Miss C. A. Raisin 2 has also contributed researches on the same lines. But no adequate account of the mineralogical nature of the peculiar Green Schists of the area was forthcoming until Sir Jethro Teall and Dr. A. Harker l examined sections of the rocks collected by other observers.

In any interpretation of the structure of this tract of country, the early observers were at a disadvantage, in the fact that no adequate geological survey of the district had been made. The task of mapping the area was undertaken by the Geological Survey, the results appearing in the 1-inch map by W. A. E. Ussher, published in 1898. Since that date the area has been mapped on the
The Earthquake of 7th August, 1895, in Northern Italy
Authors: Oldham Richard Dixon
Published: October 2009

On the 7th of August, 1895, an earthquake was felt over the greater part of Lombardy and Tuscany, and in the Alpine districts of Northern Italy. Although only a feeble shock, nowhere exceeding an intensity of IV° Mercalli, it is worthy of attention as being of unusual type, and affording an illustration of some general principles which have been deduced from the comparative study of a large number of earthquakes. The details of observations recorded are published in vol. i. of the ‘Bollettino della Societa Sismologica Italiana’ ; on pp. 162–67 reports from 81 distinct localities are given, mostly with little more information than a mere record of an earthquake, but a certain number contain fuller details. These localities are plotted on the map accompanying this paper (p. 232), which also gives an epitome of the pertinent facts recorded.

The time, as shown by continuous-record seismographs, was about 20h. 50m., mid-European time; the area, over which there is a practically continuous series of records, is approximately triangular, the sides being about 160 miles in length, making the seismic area about 15,000 square miles, and possibly about 20,000, if the shock is included, which was felt, at about the same time, at several places in the Island of Elba. The report, from Portoferraio, is attributed without question to the same earthquake, but it may have been an independent shock, approximately coincident in time with the larger one. In favour of this supposition may be placed the fact that the nearest locality
On a Collection of Fossil Plants from the Falkland Islands
Authors: Seward Albert Charles , Walton John
Published: October 2009

In May, 1922, I received from Dr. H. A. Baker, F.G.S., a collection of Permo-Carboniferous plants from the Falkland Islands which, with the consent of the Colonial Office, was entrusted to me for examination and description. At a later date additional specimens were received, some of which, although unfortunately too imperfectly preserved to be determined, were from rocks classed as Devono-Carboniferous. The Permo-Carboniferous material was collected on George Island and Speedwell Island off the southern extremity of East Falkland, also at North Arm, Bay of Harbours, near the southern extremity of East Falkland; while others were found at Cygnet Harbour and Egg Harbour on the western coast of Lafonia (the southern peninsula of East Falkland), and at Dos Lomas on the north-western coast.

In the examination of the fossils I have been assisted by Mr. John Walton, of St. John's College, Cambridge, who is responsible for the description and determination of the fossil wood.—[A.C. S.]

Subsequent to Charles Darwin's visits to the Falkland Islands little attention was paid to their geology, until the Archipelago was visited in 1901–1902 by Prof. J. G. Andersson and other members of the Swedish South Polar Expedition. The results then obtained were considerably extended by a second Swedish Expedition in 1907–1908, under the direction of Dr. C. Skottes-berg. Dr. T. G. Halle, of Stockholm, who was a member of that expedition, contributed to the Bulletin of the Geological Institute of the University of Uppsala, in 1911, a very valuable account of the geological structure and
A Micrometric Study of the St. Austell Granite (Cornwall)
Authors: Richardson William Alfred
Published: October 2009

The St. Austell granite-mass has attracted considerable attention in the past, because of the economic importance of its mineral deposits and the petrological problems that arise out of the wonderful display of pneumatolytic activity manifested in the district. The principal references to the literature are given in the footnote, and since these contain full bibliographies, it is unnecessary to compile another for the purpose of this paper.

Two reasons induced me to undertake this work. In the first place, it appeared desirable to develop and apply to a coarse-grained igneous rock-mass quantitative microscopic methods. Secondly, it seemed probable that much light could be thrown upon the problems of the St. Austell granite by quantitative and qualitative data obtained from a larger number of representative slides than has been available hitherto. A preliminary investigation in the field soon revealed that the district presented some disadvantages in the application of the method, owing to the occasional occurrence of very coarse porphyritic structure in the granite; but, at the same time, it was evident that the results would outweigh a little uncertainty arising from this difficulty.

The present paper deals solely with the granite, and all post-consolidation and metamorphic changes are excluded from its scope. The aim has been to ascertain what evidence exists of differentiation and variation in the original rock. Certain pneumatolytic effects have been generally recognized as inextricably bound up with stages in the intrusion and crystallization of the original magma, and such, of course, come within the purview of
The Barrowell Green (Lea Valley) Arctic Flora
Authors: Reid Eleanor Mary , Chandler Marjorie Elizabeth Jane
Published: October 2009

The Barrowell Green material was examined by Mr. Reid in the spring of 1916. By the request of Mr. Hazzledine Warren we have re-examined it, with the result that we have added a few new species and made a few alterations in Mr. Reid's list. In this list a species of
Cochlearia
is recorded. In other Lea-Valley deposits and in the Cam-Valley deposit fruits were found, and the determination was correct; but at Barrowell Green we have only seen seeds referred to this species, and in this case the determination was incorrect, the seeds being those of a
Cerastium
allied to
C. vulgatum
Fries, an Arctic species. It is possible, of course, that there were pods which we have not seen.

With regard to the description of this deposit, we cannot do better than quote Mr. Reid's original description from his letter of February 4th, 1916, to Mr. Warren:— ‘The Barrowell Green flora certainly points to the same period as the floras of the other Lea Valley localities. It shows the same Arctic or Sub-Arctic conditions, and contains several of the same peculiar plants, such as
Silene cælata, Linum Præcursor, Salix Lapponum
and the undetermined
Cochlearia
. No doubt the list includes about a dozen species which have not yet been found at Angel Road, Hedge Lane, Ponders End, or Temple Mills; but none of these are significant species; that is to say, they are species that one would expect to find at the other localities, if the plants from each
On Reptilian Remains from the Karroo Beds of East Africa
Authors: Haughton Sidney Henry
Published: October 2009

The fossil remains described and discussed in this paper were taken from about the middle of the Karroo Beds near Tanga, on the coast of the Tanganyika Territory, by Mr. F. P. Mennell, F.G.S., who was good enough to forward the specimens to me for examination. They consist of portions of three animals, of which one is too weathered and too fragmentary for investigation. The other two are preserved on slabs of hard, blackish, somewhat micaceous shale; the more complete animal is smaller than the other, but, as will be seen in the sequel, in other respects they are sufficiently similar to be considered representatives of the same species.

It is not necessary to dwell on the importance of Mr. Mennell's discovery. From extra-South African areas very few of its animals have been found within the ancient boundaries of Gondwanaland: that some of them were spread outside its confines is well-known; but hitherto there has been a big geographical gap between the South African localities yielding a (Gondwana fauna and those of Europe. This discovery marks the first step in the bridging of that gap; and I am extremely grateful to Mr. Mennell for giving me the opportunity of placing it on record.

Of the described specimens, the smaller and better is placed in the Rhodesian Museum, Bulawayo; the other is in the collection of the South African Museum at Cape Town.

As preserved, the specimen has a length of about 380 mm. There are missing, however, the whole of
Contact-Metamorphism in the Comrie Area of the Perthshire Highlands
Authors: Tilley Cecil Edgar
Published: October 2009

British petrographic literature is now so enriched by the detailed descriptions of contact-metamorphic aureoles, associated with plutonic intrusions—investigations largely conducted by the officers of the Geological Survey, and partly by independent workers—that it might appear that an investigation of an additional contact-zone would bring to light little but the usual well-known mineral-assemblage of aureoles already investigated: In the case of the aureole surrounding the Carn Chois diorite-complex of Perthshire, moreover, an inspection of the 1-inch Geological Survey map would tend to confirm this view—not only as to the nature of the mineral-assemblages, but also as to their apparently restricted variety. The diorite-complex is shown as intruded almost completely within the Ben Ledi Grit stratigraphical zone, touching only at its southernmost point rocks essentially of argillaceous composition— the Aberfoyle Slate-band.

Here, then, are presumably sediments of a restricted range of composition; the hornfelses derived from them may be expected to show the same limit of variation.

The examination that I have been able to make of this aureole shows quite clearly, however, that such a restriction in chemical composition is far from being the case. The thermal products show a wide range of composition, and the mineral-assemblages in the inner zone of hornfelses include types which (I believe) have not been previously recorded from British contact-zones, and some that I have not been able to match with any of the thermal products of extra-British contact-aureoles. Moreover, these unusual mineral-assemblages are by no means rare in the aureole itself, but have been
The Avonian of the Western Mendips, from the Cheddar Valley Railway to the Sea, West of Brean Down.
Authors: Bamber Agnes Elizabeth
Published: October 2009

In this paper a comparison is made between the Avonian of the Western Mendips and (
a
) the Avon Section and (
b
) the Burrington Combe section. The outcrops of the Carboniferous Limestone zones, classified according to the notation of the late Dr. A. Vaughan, have been mapped.

Levels from K
2
to S
1
are exposed in the area. The lithological and palæontological characters of the zones are described. Considerable faulting and folding occurs, more especially in the west of the region.
The Lower Carboniferous Succession in the Settle District and along the Line of the Craven Faults
Authors: Garwood Edmund Johnston , Goodyear Edith
Published: October 2009

The district which is the subject of the present communication has attracted the attention of geologists since the days of Playfair (46) who, in his ‘Illustrations of the Huttonian Theory’ published in 1802, alludes to a visit that he paid, with Lord Webb Seymour, to Chapel-le-Dale and Thornton Force, and describes the unconformity between the Carboniferous Limestone and the underlying slates. Sedgwick (50), in a paper read before the Geological Society in 1831, described and illustrated the succession of the Carboniferous rocks which occupy the country between Penyghent and Kirkby Stephen. That paper, which shows a keen insight into the general structure of the district, was not printed in the Transactions until 1835.

The same year saw the publication of John Phillips's (44) classic work—‘The Illustrations of the Geology of Yorkshire’ the second part of which, ‘The Mountain Limestone District’, was issued in the following year. Phillips confined his attention to the lithological succession, and made no attempt to describe the distribution of the fossils, or to make use of them for the subdivision of the series, the palæontological portion of the work forming really an independent communication. It was impossible, however, that so careful an observer should fail to notice that certain fossils were more abundant at some horizons than at others, and, although he does not allude to this fact in the work mentioned above, it is evident that it did not entirely escape his notice: for, in his Presidential Address (45, pp. xxxviii-xxxix) to the Geological Society
The Development of the Severn Valley in the Neighbourhood of Iron-Bridge and Bridgnorth
Authors: Wills Leonard Johnston
Published: October 2009

The late Prof. Charles Lapworth inspired me with a desire to test the validity of his hypothesis, put forward as long ago as 1898, that the Upper Severn was added to the Lower Severn as a result of the impounding of a glacial lake in Shropshire and Cheshire. The lake, according to the hypothesis, rose until it flowed out over the former watershed between the Shropshire plain (which originally had drained to the Dee or the Mersey) and the headwaters of a tributary of the Worcestershire Stour.

The same view was put forward independently by F. W. Harmer in 1907, in a paper accompanied by an excellent contoured map, which may be conveniently consulted in connexion with the present work.

Neither Lapworth nor Harmer attempted, so far as I know, to bring forward detailed evidence in support of the hypothesis. Lapworth called attention to the rejuvenation of the Severn and its tributaries, which he regarded as resulting from the diversion, into a diminutive tributary of the Stour, of the copious waters of the Upper Severn which had originally flowed into the Dee; while Harmer pointed out the existence of Glacial lake-deposits on the Shropshire Plain.

Harmer threw out the suggestion (
op. cit.
p. 479) that the Severn Valley from Bridgnorth to Bewdley was initiated as a marginal drainage-channel on the west side of the ice-lobe that left so many Scottish and Lake-District boulders around Wolverhampton and Bridgnorth.

As may be seen from any contoured map, the Cheshire-North Shropshire Plain is
On a Recently Discovered Breccia-Bed underlying Nechells (Birmingham), and its Relations to the Red Rocks of the District
Authors: Boulton William S.
Published: October 2009

For many years it has been known that certain breccias occur immediately below the Bunter in the Birmingham district, irrespective of the well-known development in the Clent Hills and near Northfield, about 7 miles south-west of Birmingham. In 1890 C. J. Gilbert described such breccias at the base of the Bunter Pebble-Beds in Sutton Park, 7 miles north of the city, and showed that they lie with pronounced unconformity upon red clays and sandstones, and are covered unconformably by the Bunter Pebble-Beds. During the last ten years, my attention has been directed from time to time to similar occurrences at the base of the Bunter met with in borings for water in and around Birmingham. In the recent re-mapping of the district by the Officers of the Geological Survey, a considerable development of these breccias has been noted, more especially at Hopwas, 2 miles west of Tamworth, and in the district round Little Aston and Streetly, a little to the north of Sutton Coldfield. Mr. G. Barrow has proposed the name Hopwas Breccia for these beds, and a description of them and their relationship to the Trias above and the Carboniferous below will be found in the recently published Lichfield Memoir.

It is evident, however, that the Geological Survey is still in doubt as to the geological age of these rocks. In the Lichfield Memoir they are classed as Permian (?), and in the accompanying 1-inch map they are bracketed with the Trias; while the relation of the Hopwas to
The Geology of Southern Guernsey
Authors: Farquharson Donald John
Published: October 2009

Guernsey, the second largest of the Channel Islands, has been described geologically in varying amount of detail by a number of previous investigators, who for the most part confined their attention to the northern portion of the island, and there are only scanty references to the metamorphic complex forming the southern portion. In 1884 the Rev. Edwin Hill & Prof. T. G. Bonney (6) announced the result of their first visit to the island, and gave a few general notes relating to the southern gneisses which they believed to be, as a whole, comparable with the Laurentian Gneisses of Canada. No attempt was made to distinguish between the various types of gneiss which are now known to occur in that area.

In a paper on Alderney Canon Hill (7) discussed the age of the Channel Island rocks and, incidentally, announced his conclusion that the ‘Guernsey Gneiss’ is mostly—perhaps all—of igneous origin, but subsequently crushed. The conclusions of the two writers above mentioned may be summarily stated as follows:—In all the islands there are plutonic rocks—diorites and hornblende-granites—which are posterior to the gneisses and other dynamically altered rocks, but are believed to be pre-Cambrian, since in Jersey these rocks are overlain by the Rozel Conglomerate (basal Cambrian) and in Alderney are succeeded unconformably by grits correlated with the Conglomerat pourpré (Ordovician).

The main object of the present paper is to give a description of the distribution, field relations, and petrographic characters of the different types which together make up the metamorphic
Descriptions of Gasteropoda, chiefly in Mrs. Robert Gray's Collection, from the Ordovician and Lower Silurian of Girvan
Authors: Longstaff Jane
Published: October 2009

Since this contribution to the knowledge of the more ancient Palæozoic gasteropoda is primarily concerned with those from the Girvan district, contained in Mrs. Gray's magnificent collection, reference is made to others only where they afford further information concerning structure or distribution. Forty-one forms are dealt with, seven of which have been described and one named in MS. by previous authors.

Twenty-four species and one variety from the same district were described and figured by me in papers read before this Society in the years 1899, 1902, 1905, and 1906. Of these twenty-one species and a variety belong to genera referred to the Pleurotomariidæ; and now twenty-five species and a variety are added to this number.

I am following Dr. E. O. Ulrich in his classification of the family, only making exception in the case of
Omospira
. He considers this genus more akin to
Raphistoma
Hall. It is, however, distinguished by having a sinus in the outer lip at the periphery, also a band on most of the whorls; this latter is never present in
Raphistoma
according to Hall, and also according to Dr. Ulrich himself. So far, I have not met with any specimens bearing the characteristics of
Raphistoma
sensu stricto in the Scottish Ordovician. The internal moulds of certain forms have been mistaken for that genus; but, where the structure is preserved, as will be pointed out, there can be no doubt that they belong to
Liospira
Ulrich.

In what degree these ancient forms are really related one
The Old Red Sandstone of the Cardiff District
Authors: Heard Albert , Davies Richard
Published: October 2009

The district which forms the subject of this communication is situate immediately north of Cardiff. It is bounded on the east and west by the Rhymney and Taff Valleys, and on the north by the Carboniferous rocks of the South Wales Coalfield. The area thus denned is about 16 square miles in extent.

We began a systematic petrological investigation of the Old Red Sandstone of this district in the hope that a more detailed knowledge of the sediments would establish a clearer conception of the conditions of deposition, of the probable source of the rocks, and of their relation to the underlying and overlying stratigraphical divisions. During the course of the work certain fossil localities were discovered. These represent the first records of Old Red Sandstone fossils within the area defined above.

The Old Red Sandstone of South Wales, which crops out round the greater part of the South Wales Coalfield, is a continuation of the Herefordshire outcrop; but, in the neighbourhood of Cardiff, it differs considerably in thickness from many other parts of the Old Red Sandstone around the Coalfield Syncline, and more especially from that of the North Crop.

There is a general lithological resemblance between the Old Red Sandstone rocks of the Cardiff district and those of the North Crop, although there are certain differences at particular horizons (see p. 496).

Prof. W. J. Sollas estimated the total thickness of the Old Red Sandstone of the Cardiff area to be 4273 feet, making his measurements along a
On an Olivine-Dacite in the Tertiary Volcanic Series of Eastern Iceland: the Rauthaskritha, Hamarfjord
Authors: Hawkes Leonard
Published: October 2009

The flow of dacite to be described crops out in the face of the cliff bordering the north of Hamarfjord—one of the deep incisions into the Tertiary basalt-plateau of South-Eastern Iceland. A mass of acid rock occurring in a district entirely built up of dark basaltic lavas—it attracts attention by reason of the light colours of its different lithological members, and its unusually abundant screeformation. It is known as the ‘Rauthaskritha’, or ‘red scree’, and has been described by all geologists who have visited the district.

C. W. Paijkull examined this occurrence of ’trachyt‘, and regarded it as a dyke, giving a diagrammatic section in illustration (2). The dyke is shown more than half a mile thick cutting through the basaltic series, and terminated above by one of the basalts. A glassy facies is observed at the two vertical margins and also on the top. The mass exhibits contorted banding, and is cut by dolerite-dykes which fail to penetrate the overlying basalts. The country-rocks are quite undisturbed, and no suggestion is put forward as to how room was made for this remarkable intrusion. Other writers, Th. Thoroddsen (12) and A. Helland (6), have admitted the intrusive nature of the rock.

After making a detailed examination of this occurrence in the course of three summer visits, I have come to the conclusion that it represents a lava-flow.

These are regularly bedded plateau-basalts with interbasaltic partings of red lateritic deposits, dipping 5° to 7° westwards. Magnificent sections from 2000 to 3000 feet
On the Skeleton of
Iguanodon atherfieldensis
sp. nov., from the Wealden Shales of Atherfield (Isle of Wight)
Authors: Hooley Reginald Walter
Published: October 2009

I. Introduction.

This very fine fossil was obtained from the débris of Wealden Shales, after a fall of the cliff near Atherfield (Isle of Wight). The complete skeleton was probably present when
in situ
, and the missing portions were carried away by the heavy seas, which scoured the foot of the talus for several days, preventing all search for the bones except at low tide. When its discovery was announced in 1917, the disarticulated bones of the skull were lying scattered among the bones of the body and limbs in many blocks of the matrix. The unfused condition of the elements of the skull proved the skeleton to be that of a young individual, and as, notwithstanding this fact, there were six anchylosed vertebræ in the sacrum, it was identified as a specimen of
Iguanodon bernissartensis
, and the portion of the integument found was described as belonging to that species. The study of the bones, after they had been cleared of the matrix and restored, has, however, proved the fossil to belong to a new species, and hereafter it will be designated
Iguanodon atherfieldensis
. The estimated length of the skeleton is 6·3 metres (about 21·6 feet).

The elongation of the facial part of the skull, the transverse expansion of the edentulous portion, the great constriction between that and the frontal area, the broad and square cranial region, and the heavy mandible agree with
I. mantelli
and
I. bernissartensis
. The skull is intermediate in build between the graceful skull of the
A New Catopterid Fish from the Keuper of Nottingham
Authors: Swinnerton Henry Hurd
Published: October 2009

The material for the investigation which is the subject of this paper was found in the year 1912 at Woodthorpe, an estate which lies just beyond the borough boundary of the city of Nottingham. During the development of this estate for building purposes several deep sewer-trenches were made: these passed through the base of the Keuper Waterstones, which in this district is clearly defined by the presence of a layer of conglomerate usually not more than 6 inches thick. Above this is a compact, fine-grained, yellow sandstone about 2 feet thick, which splits easily along certain planes determined by the presence of thin films of clay. The surfaces of the slabs thus formed were either irregularly undulating, or quite flat.

In the case of the slabs with undulating surfaces numerous well-preserved remains of
Semionotus
were found embedded side by side in the rock, at a depth of from one-eighth to a quarter of an inch below the surface. This mode of occurrence was strongly suggestive of the habit exhibited by some existing freshwater fishes. In dry seasons, when there is a danger of the water drying up, they bury themselves in shoals in the mud at the bottom of the canal or pool in which they live, and remain there until the water is renewed. For the particular fossil fishes under discussion this renewal evidently came too late.

In the case of the slabs with flat surfaces the number of fishes was smaller; and each lay with the trunk, tail
A Preliminary Survey of Metamorphic Zones in the Southern Highlands of Scotland
Authors: Tilley Cecil Edgar
Published: October 2009

I. Introduction.

Thirty-one years ago, Mr. George Barrow (1) presented to this Society his classic account of the intrusion phenomena of a group of ‘Older Granites’, in the Forfarshire area of the South-Eastern Highlands. That paper is distinguished by reason of the clear enunciation of the two outstanding conclusions to which the author was led. In the one was illustrated for the first time the effect of crustal stresses on the differentiation-course of igneous magma, a process which plays so important a part in present-day theories of petrogenesis; in the other, also for the first time, was indicated the subdivision of a group of highly-metamorphosed sediments into metamorphic zones characterized by the presence of critical index-minerals. So far as I am aware, his paper represents the first attempt in petrological literature to bring precision to the study of regional metamorphism, by laying upon a map zonal lines indicative of varying grades of metamorphism.

It is chiefly upon this aspect of Barrow's work that I shall dwell in the matter now set forth.

Nineteen years later (2) he extended the area of his zonal metamorphic map, at the same time increasing the number of zones. The map presented to the Geologists' Association thus covers the ground included in the quarter-inch sheet (No. 12) of the Geological Survey map of Scotland, extending to the Highland Border from Stonehaven to Dunkeld. In the meantime, other Scottish investigators by extended surveys of Perthshire and Argyllshire were bringing to light new data on the metamorphism
Petrographical Notes on the Stockdale Shales
Authors: Rastall Robert Heron
Published: October 2009

A.

Atrypa-flexuosa
Zone, Skelgill.

This consists in part of finely-divided micaceous material, with chlorite of the usual type, and some quartz, but there is also a considerable amount of carbonate, and the rock effervesces freely with cold dilute acid. It differs therefore notably from the others, and may be described as an impure limestone [20,008].

B.

Green Streak,
Argenteus
Zone, Skelgill (with parts of adjoining graptolitic mud-bands).

This specimen shows very pronounced colour-banding. The pale greenish-grey ‘streak’ is strongly differentiated from the other part, which is dark-grey. On ignition for 30 minutes, the ‘green streak’ becomes somewhat paler, nearly white; and the dark bands are reddened.

Under the microscope the ‘green streak’ is seen to be closely similar to the Browgill Shale (G, p. 132), though of somewhat finer texture, and with much more pronounced orientation of the flakes of mica and chlorite. Grains of quartz determinable under a half-inch objective are quite rare.

The dark rock enclosing the streak, which belongs to the graptolitic bands, appears to be essentially of the same composition, although the structure is partly obscured by the presence of a large amount of dark brownish-black material. Since this reddens on ignition, it is probably in part ferrous sulphide and in part carbon [20,006].

C.

Green Streak, Pont Erwyd

This is quite similar in composition and general character to the ‘green streak’ from Skelgill, but slightly coarser in texture: very angular fragments of quartz are easily visible incertain bands.

The Rock
The Development of
Leptoplastus Salteri
(Callaway), and of other Trilobites (Olenidæ, Ptychoparidæ, Conocoryphidæ, Paradoxidæ, Phacopidæ, and Mesonacidæ)
Authors: Raw Frank
Published: October 2009

I. Introduction.

The above-named species of Olenid was first recorded in 1874 by Callaway from the Shineton Shales of Shropshire, which he then claimed as of Tremadoc age.

It was described from imperfect material as a
Conocoryphe
, which name in 1877 he corrected to
Olenus
, giving at the same time a description of the entire trilobite.

A specimen for the first time exhibiting dorsal spines was in 1900 described by Dr. H. H. Thomas under a new name,
Olenus mitchinsoni
. An additional occurrence of the species was in 1905 recorded by Prof. W. G. Fearnsides under the name of ‘
Parabolinella salteri
’. It occurred in the upper part of his Nant-ddu or
Bellerophon
Beds, which follow next above the
Dictyonema
Band north-west of Arenig Fawr, and it is there accompanied by
Asaphellus homphrayi
Salter and
Parabolinella triarthrus
(Callaway), which species are also associated with it at Shineton. In 1907 I briefly described its development, and assigned it to a new sub-genus ‘
Leptoplastides
’. Finally, Mr. P. Lake redescribed it in 1919, under the name
Leptoplastus salteri
.

It is now many years since, at Prof. Charles Lapworth's suggestion, I undertook the study of the trilobite fauna of the Shineton Shale. The first collection studied was that collected by Mr. Rhodes for H.M. geological Survey, and lent to Prof. Lapworth by the then Director-General. Among these were several slabs covered with minute examples of the fossil in question, in different stages of development; and the early stages seemed so strange and unexpected that a special study
Appendix: On the Cooling of a Dyke
Authors: Hilton H.
Published: October 2009

The physical conditions of a dyke on and after intrusion are so little known, that we cannot hope to obtain precise information as to the rate of cooling by mathematical calculation.

We make the assumptions (1) that κ is the same for the country-rock and the dyke, where κ=K/cp, ρ (> being the density,
c
the specific heat, and K the conductivity, (2) that the dyke and country-rock obey the ordinary laws of heat-conduction, so that lack of homogeneity, latent heat of crystallization, etc. are neglected. These assumptions are, of course, inaccurate, but may enable us to obtain a rough approximation to the truth.

If θ be the temperature at a point at a distance
x
from the middle of the dyke in a direction perpendicular to its walls, then, after an interval of time
t
,

which is satisfied.by

This is the solution corresponding to the assumption that, when
t
=0: that is, at the time immediately after the intrusion of the dyke, the width of which is 2
a
,

θ = Θ when
x
2
<
a
2
, θ=½Θ when
x
2
=
a
2
, and θ=0 when
x
2
>
a
2

.

If we put
u
2
= 4κ
t
ν
2
when
x
=0 and (
u
−
a
)
2
= 4κ
t
ν
2
when
x
=
a
, we get for the temperatures at the centre and edge of the dyke: where 4κ
tn
2
=
a
2
.

Taking, for example, Θ = 800,
a
= 150, K = ·OO4,
c
= ·23, ρ = 2·8, we have
t
= 900,000/
n
2
in the centigrade and c.g.s. system; wherefore the time elapsed
The Geology of the Llandovery District: Part 1.—The Southern Area
Authors: Jones Owen Thomas
Published: October 2009

I. Introduction.

Near the small market-town of Llandovery, in the Towy Valley, the main river flowing southwards from the direction of Rhandirmwyn is joined by two important tributaries. East of the town the River Gwydderig enters from the east, and joins the Brân, which flows south-westwards along a strike-valley from the direction of the Sugar Loaf, between Llandovery and Llanwrtyd Wells. The town lies on an alluvial flat between the Towy and the Brân, which enters the main river about a mile below. It is served jointly by the Great Western and the London, Midland, & Scottish Railways. From the Sugar Loaf to Llandovery the railway skirts the valley of the Brân, and below the town it continues in the same direction along the broad floor of the Towy towards Llandeilo, Carmarthen, and Swansea. Between Llandovery and Llangadock, 6 miles below, there is a main road on each side of the valley, that on the north side being the more frequented. The district is included in the 1-inch Geological Survey map, Sheets 41 & 42 N.W. (Old Series); in the 1-inch Ordnance Survey map, Sheets 212, 213, & 196, and in the 6-inch sheets, Carmarthenshire 10 S.E., 11 S.W., 18, 19 N.W., 26 S.E., 27 N.W. & S.W.

The rocks near the town belong to the upper part of the Bala formation, but at the Sugar Loaf, 7 miles away to the north-east, a lower part of that formation, including the
Dicranograptus
-Shales, is rolled up in the core of a
The Stratigraphy of the Laki Series (Lower Eocene) of parts of Sind and Baluchistan (India); with a Description of the Larger Foraminifera contained in those beds
Authors: Nuttall Winfred Laurence Falkiner
Published: October 2009

I. Introduction.

The following is a short account of the geology of the Lower Eocene Laki Series of the neighbourhood of Tatta, Meting, and the Laki Range in Sind, as well as of beds of the same age in the Bolan Pass (Baluchistan). The location of these places can be readily determined by reference to the map (fig. 1, p. 418). The first part of the paper includes a revision of the existing classification of the geological succession, and a brief description of the stratigraphy. In this respect the neighbourhood of Meting is of particular interest, as the highly fossiliferous lowermost beds of the Laki Series are well exposed, and so far in this area the true geological succession appears not to have been recognized.

The second part incorporates palæontological details, in particular with reference to foraminifera of the genera
Alveolina, Nummulites, Assilina
, etc. It is remarkable that several species with a limited stratigraphical range occur associated, just as they are in beds of similar age in Europe. The Indian representatives of these species have not been systematically examined or described since the classical Monograph on Nummulites by J. d'Archiac & E. J. A. Haime in 1853. At that time, specimens were not collected and separated according to their stratigraphical horizons, nor is it clear often which of the figures to specimens from India.

The field work in the area was done during the winter of 1920–21 and in the latter part of 1923, when most of the fossils described
The Geology of the Cader Idris Range (Merioneth)
Authors: Cox Arthur Hubert
Published: October 2009

I. Introduction.

The mountain-range of Cader Idris is formed by a great escarpment of Ordovician volcanic rocks which looks northwards across the Mawddach estuary towards the extensive area of Lower Cambrian rocks comprised in the Harlech Dome. The range has a general east-north-east to west-south-west trend, but the central portion runs almost due east and west. Along the range from east to west are the following summits, all exceeding 2000 feet in altitude:—Geu Graig, Mynydd Moel, Pen y Gader (2927 feet, the highest point), Cyfrwy (or The Saddle), Tyrau Mawr, and Craig y Llyn. Situate a little south of the main escarpment, but connected with it by cols, are the heights of Mynydd Pencoed and Craig Cau. The range is bounded on the south by the Talyllyn Valley, and on the north by the valley running from Dolgelley past Llyn Grwernan. Both these valleys trend nearly north-east to south-west, and follow the lines of repeating faults; along them run the chief and almost the only roads within the district mapped.

North of the Llyn Grwernan Valley a smaller hill-range, or rather a series of ranges, intersected by the Gwynant Valley, intervenes between Cader Idris and the Mawddach estuary. The greater part of the area included in the map (PL XXXVII) lies above the 1000-foot contour, much of it indeed above the 2000-foot line, so that most of the ground is uncultivated and given over entirely as pasturage for sheep. Cultivated ground is restricted to small patches along the Llyn Gwernan
On a
Sagittal Section
of the
Skull of
Australopithecus Africanus
Authors: Sollas William Johnson
Published: October 2009

That the Taungs skull represents the youthful form of a remarkably interesting kind of Ape has been made abundantly clear by the descriptions given of it by its discoverer and by my friend Dr. R. Broom. For fuller knowledge we must await the detailed account which Prof. R. A. Dart is now preparing, and the casts with which we hope that he will provide us.

Meanwhile we may learn something from a preliminary sagittal section, which I owe to the kindness of Dr. Broom and the generosity of Prof. Dart, who permitted him to trace it.

Fig. 1 (p. 2) is a reproduction of this section. The absence of any suggestion of a frontal torus, the small angle made by the nasion (ν) radius with the nasi-lambda (N.L.) axis, and the proximity of the nasion to the anterior termination of the brain will be seen at a glance. These are characters rather human than simian, and combine to give the forehead a striking human appearance, so much so as to suggest that ‘Homunculus’ might not inappropriately have been chosen for a surname.

The significance of these and other features may be best illustrated by comparison with similar sections provided by other members of the Primates. But, first of all, it is necessary as a preliminary to point out the capital importance of confining our comparisons to skulls in one and the same stage of development. This will be best appreciated by reference to the following illustrations. In fig. 2 the