The Archæan (Pre-Cambrian) rocks of Britain have of late years received considerable attention, owing partly to the more or less complete working out of the younger groups, and partly, perhaps, to the fascination which attends a study of peculiar complexity. Whatever interest attaches to the correlation of formations which can be easily identified by their organic remains, or which can be traced across country for scores of miles in unbroken lines, it will be readily understood that the spirit of inquiry will be strongly piqued when it is challenged to construct orderly systems out of rock-masses to which the ordinary tests can be but partially applied. Yet much has been done towards the establishment of a succession amongst these ancient groups. In America, Dr. Sterry Hunt describes six distinct systems.

The description of sandstone samples, defined by three components, is introduced through non-parametric sample density description. The composition of a particular sample defines a direction from the origin of the Cartesian reference frame. Radial difference between individual samples then provides the measure of their similarity. A sample set can be viewed as a bundle of compositional axes with a corresponding density distribution on both the ternary diagram (or unit constant sum plane) and the positive octant of the unit sphere. Because radial differences are disproportionately displayed on the ternary diagram, radial density calculations on the sphere are to be preferred. The mode of the sample set, the implied centre of greatest data concentration, is considered to be the most meaningful representative value, as the component joint mean can lie outside the data field with certain data configurations. In addition, the component joint mean cannot provide a useful representative composition for samples drawn from a bimodal distribution. Sample density distribution not only provides a data defined approach to describe sample dispersion, but also furnishes an indication of sample sufficiency in displaying the degree to which modes are supported by surrounding observations.

One of the most notable additions made to the Gallery of Fossil Reptilia in the Natural History Museum during the last few years is the beautifully preserved Plesiosaurian skeleton which is represented in Plate IX.

The accompanying section shows the succession of beds from the Harlech grits, near the sixth milestone on the road from Dolgelly to Trawsfynydd, across their strike in a south-easterly direction, to the lower ash-bed of the Arenig group at the farm of Blaenau, five miles north-east from Dolgelly. In this section all the beds occur in regular sequence, although they are invaded by many intrusive masses and dykes of diabase; only the larger of which are shown in my section, as it would be impossible, on so small a scale to depict the innumerable protrusions of this rock that occur in the district. The section crosses, at Moel-Cors-y-garnedd, the southern flank of the mountain Rhobell-fawr, which is the largest mass of diabase in Wales. All along the eastern side of Rhobell-fawr the strata are completely inverted, as shown in diagram, so that the Festiniog beds (5 and 6) lie above the more recent Dolgelly beds (7 and 8), from underneath which the Tremadoc beds (9) come up, overlying the beds of slates and ashes belonging to the Arenig Group (10 and 11).

It is worth while to examine the value and definition of certain of the older generic or sub-generic groups, for there is much difference in the usage of the terms, and in the interpretation of their rank and value. This is especially the case with Acaste and Phacopidella, for the author of the latter name wrongly included in it such forms as Ac. downingiae and others of a diverse type, though they differed in important particulars from the species Ph. glockeri Barr. which he chose as the type of Phacopidella as above observed (see Glockeria). Other new and old generic terms appear to have been also used in too broad a sense, and there is no general agreement as to their limitation.

In 1900 Mr. R. Bullen Newton described the casts and impressions of some lamellibranch shells, in blocks of fossiliferous sandstone from Kuala Lipis, Pahang.1 On account of the prevalence of specimens which he assigned to the genus Myophoria, Mr. Newton called the rock “Myophorian Sandstone”. Amongst other species identified by Mr. Newton Chlamys valoniensis has a wide distribution, “and is characteristic of the Ehaetic or uppermost Trias. It is to this horizon, therefore, that the Myophorian Sandstone must be referred”.

The Rhaetic section at Newark is described and compared with sections further south. The Lower Rhaetic is locally sub-zoned by constant bone-bed horizons. In the south-west of the area a much richer fauna occurs and the zone-fossil Pteria contorta appears lower in the succession. The explanation offered is that a lagoon phase existed in the more northerly district.

Zoœcia roughly elliptical, length ·60 to ·68 mm., width ·36 to ·40 mm., length of area ·36 to ·40 mm., width ·24 to ·28 mm.; they have broad side walls, whose upper surfaces slope slightly to the area; at the foot there is generally a fair amount of external front wall, which often carries its own accessory avicularium or the oœcium of the preceding zoœcium; the walls of adjacent zoœcia are always distinguishable and very often not in contant.

During an examination of the complicated series of Lower Palæozoic rocks in County Waterford, with which I am still engaged, I have had the opportunity of collecting largely from the few fossiliferous beds in the neighbourhood of Tramore, and a study of the fossils throws considerable light on the vexed question of their age. It is not my intention in this paper to discuss the relations of the igneous and sedimentary rocks, nor to attempt to explain the structure of the district.

England has only had one Glacial Period. G. W. Lamplugh pointed this out in 1906 before the British Association at York, and quite lately also in 1913 before the International Geological Congress in Canada. No one has yet attempted to contradict it.

The two chief difficulties in taking serial sections are to ensure that the successive sections are all parallel to each other and to obtain reliable drawings of them.

SOME years ago, hard limestones containing corals were discovered cropping out in the railway cutting at Km. 65 near Tulkarem. These contain various coral types, but it was found impossible to determine their age. Since that time, reef limestones with abundant calcareous algae (Lithothamnium) and Hydrocorallines of the Millepora group have been found in various localities and are the first Miocene rocks to be recorded from Palestine.

MR. Bailey has very kindly permitted me to see his manuscript, and also to examine a specimen and slice of the rock which he regards as a volcanic breccia underlying the pitchstone. Since he attaches some importance to this rock, I will consider it first.

The natural base of the thick pitchstone sheet is made by a band of more glassy aspect, almost like an obsidian. The microscope shows that this, apart from the usual enclosed crystals, is a light-brown glass, free from the crowds of crystallites found in the ordinary pitchstone. Another feature is that it encloses numerous little fragments of basalt. These indeed, with occasional larger pieces, pass up for some feet into the pitchstone, but they are most abundant near the lower surface. Such inclusions, picked up from the contiguous rocks, may occur both in lava-flows and intrusive sills, but, so far as my experience goes, are more frequent in the latter. The obsidian-like band is well seen, fresh and intact, at places on the northern side of the SgÙrr; but elsewhere it is much brecciated, and usually much decomposed in addition. The brecciation is of such a kind that pieces of the normal pitchstone have become mingled with the debris of the more glassy variety. Mr. Bailey has quoted part of my description of this brecciated basal band as it is exposed, in a decomposed state, on the southern side of the ridge. That it is a part of the pitchstone sheet, not a separate underlying deposit, is there clearly demonstrated: see fig. 6 on p. 60 of my paper.

From remotely sensed images of rock surfaces at coasts it is possible to map some characteristics of different rock types. To do this a selection must be made of those parts of the image that correspond to the rock surfaces prior to interrogation of their geological information content. A comparative study of satellite-acquired multispectral Thematic Mapper data and aircraft-acquired multispectral scanner data at four test sites on the Pembrokeshire coast was made. The spatial resolution of the Thematic Mapper data (30 m) proved to be too coarse to provide any continuity of mapping over several kilometres of rock exposures, whereas the 10 m resolution of the aircraft data was adequate to do this. Using the aircraft scanner data, neighbouring Old Red Sandstone and Carboniferous (mainly carbonate) rocks could be discriminated in both three-band and principal components images. Furthermore, it proved possible to distinguish between limestone and dolomite lithologies in the Carboniferous succession and between some of the mudstones and sandstones in the Old Red Sandstone. Airborne multispectral scanning of rocky coasts is a new potential tool for geological mapping in exploration projects in which it would be best integrated with the acquisition of airborne geophysical and field geological data.

In February, 1932, the British Association Committee appointed to examine and report upon petrographic classification and nomenclature issued a questionnaire in the GEOLOGICAL MAGAZINE and in Science, in order to ascertain what measure of agreement, if any, exists among petrologists as to the principles upon which a rational system might be established.

The labours of Mr. Jex in the Eskdale fish-beds have brought to light another beautiful new fish, now in the British Museum. This is a Ganoid of the genus Elonichthys, and though represented as yet only by a single specimen, this is fortunately a very perfect one.

It is a noteworthy feature of the most ancient crystalline limestones that they are generally dolomitic, or at any rate frequently so. They often consist of practically pure dolomite; whilst associated with this in some cases is pure crystalline magnesite, which is very liable to be mistaken for saccharoidal dolomite.

The radioelement distribution and content of the Lundy granite, a coarse-grained megacrystic granite of Tertiary age, has been measured using a portable gamma-ray spectrometer in order to assess fractionation and alteration processes in the granite. Results indicate a systematic variation of K, Th and U (with a few notable exceptions) that follows a partially concentric distribution to lower concentrations inland. The plateau region of the island (particularly the southern half) is relatively depleted in all radioelements. Over the island, measurements of K vary from 1.3–4.9 wt %, Th varies from 5.0–20.3 ppm and U varies from 2.0–12.5 ppm. A petrographic, electron microprobe and autoradiography examination of the granite indicates that the radioelements mainly reside in discrete major and accessory minerals, of which K-feldspar (K), biotite (K), monazite (Th), xenotime (U), tungsteniferous columbite (U) and uraninite (U) are the most important. Uraninite is rare, being preserved only in fresh samples which come mainly from abandoned quarries. Mass balance modelling indicates that up to 76.6% of uranium could reside in uraninite and where this has been leached by secondary processes such as hydrothermal alteration or weathering then the present radioelement content no longer reflects the original rock composition. Fission track evidence is presented to show the pathways along which uranium has been mobilized from or within the granite. Secondary sites of radioelements include fractures cross-cutting all major minerals (but especially quartz), grain boundaries, altered cores of plagioclase feldspar and occasionally yellowy brown mixed chlorite/smectite replacement product after biotite. Biotite itself may exhibit secondary tracks along cleavage traces. Combined effects of crystal fractionation (primary variation) and secondary alteration best explain the distribution of radioelements, with K controlled by fractionation of the major phases K-feldspar and biotite, Th by fractionation of the accessory mineral monazite (±xenotime and uraninite) and U contents by uraninite and tungsteniferous columbite. Secondary processes have removed much of the uraninite leaving behind indeterminate Fe—U material along fractures and residual U (and Th) enrichment within altered major minerals. There is some evidence to suggest that late radioelement-bearing fluids precipitated monazite and uraniferous zircon along fractures during the waning stages of magmatic activity.