Samples of an unusual cordierite-rieh rock from near Upington, Cape Province, were collected by Dr. A. Poldervaart who kindly passed them to me for further study. This paper presents the results of the petrographic examination together with chemical analyses of the rock and of cordierite and biotite, which are two of the constituent minerals.

During a departmental excursion to South Devon in April 1951, material was collected from the Meldon aplite quarry near Okehampton, to the north-west of the Dartmoor granite, which on examination has proved to contain the mineral columbite. The mineral is present only in very small amounts and as extremely minute crystals; nevertheless its presence is of considerable interest in that this appears to constitute the first authenticated record of the occurrence of a mineral of the columbite-tantalite series in Britain.

The literature of meteoritics contains little information about the unusual Breece meteorite. This iron appears to be mentioned only in museum accession reports and catalogues of meteorite collections, and the sole information supplied by these references consists of the approximate date of find (1921), the approximate weight (50 to 51 kg.), the approximate place of discovery, near Breece, McKinley County, New Mexico, in latitude 35° 18' N., longitude 108° 18' W., and the classification (Ore). At the time of the discovery the hamlet of Breece was the centre of a small lumbering industry, since moved SW. and SE. into more heavily forested areas, and today it has few inhabitants. The find consisted of a single well-preserved mass which was purchased in its entirety from an unnamed source by the Field Museum of Chicago approximately ten years after the iron was discovered.

In the microscope designed by G. B. Amici (1844), which seems to be the very earliest polarizing microscope, the stage already possessed not only graduated concentric rotation, but also a horizontal tilting axis. It was, in fact, a built-in two-axis universal stage. Glass hemispheres were introduced at a much later date by W. G. Adams (1875) for use in a specially designed conoscope, but the Adams stage seems to have been little used (see, however, H. Schumann, 1949).

The two-axis stage as now known was designed by E. S. Fedorov (1893) and was soon followed by other forms. It is a curious fact that the four-axis stage was used almost from the beginning, though it was for some time known as the three-axis stage.

Some specimens of baryte, recently obtained from Westmorland, show up to six changes of habit during growth. This was elucidated with the aid of the colour-zoning and fluorescent zones. A change of habit is also recorded in one specimen from County Durham.

The Ballachulish slates, exposed to the north and south of Loch Leven in Argyllshire, contain, in most places, cubes of pyrite up to half an inch in diameter. During a visit to the area in the spring of 1949 the writer's attention was attracted by the dark colour of the 'pyrite' cubes in the North Ballaehulish slate quarry a little more than a mile east of Onich. On examination these proved to consist of a mass of haphazardly orientated crystals of pyrrhotine with irregular outlines. Slates collected from the main working quarry on the south shore of Loch Leven, on the other hand, contain cubes which are single crystals of unaltered pyrite.

Two new occurrences of the rare manganese mineral jacobsite (MnFe2O4) have come to light in the course of mineragraphic studies carried out as part of the research programme of the Mineragraphic Section of the Commonwealth Scientific and Industrial Research Organization. The jacobsite occurs as a constituent of small bodies of high-grade manganese ore at Weabonga, near Danglemah, and at the Mount Sally mine, about 6 miles west of Danglemah, both in the Tamworth district of New South Wales.

During the Manchester University's 1946 geological excursion to Anglesey, a visit was made to Parys Mountain. At this locality small quantities of an attractive light blue mineral were found capping pyrite veins and in clefts in the rock. Larger finds were obtained in an artificial cavern which extended for fifty or sixty feet into the south-east side of the excavated pit. A specimen weighing 2½ pounds and consisting of silicified shale veneered with the pale blue mineral was collected by the author and examined in the geological research laboratory at Manchester University during the session 1948–1949. The blue mineral was identified as pisanite, and this is the first record of pisanite as a British mineral.

Parys Mountain is situated in the north-west of Anglesey close to Amlwch. Copper and to a smaller extent lead were mined throughout a period exceeding one hundred and fifty years, but operations have completely ceased since the first world war. The geological structure of the district need only be briefly outlined for the purpose of this study.

During an examination of the mineral bayldonite, (Pb,Cu)7(AsO4)4(OH)2.H2O, for the purpose of obtaining standard X-ray powder data to compare with supposed single crystals of this species, it was found that a specimen purchased in 1948 as bayldonite from Ojuela mine, Mapimi, Durango, Mexico (B.M. 1948,267) gave a powder pattern related to those of members of the descloizite group and fairly close to but not identical with conichalcite, CuCaAsO4OH. It chanced that about the same time a specimen of a green botryoidal mineral from Brandy Gill, Caldbeek Fells, Cumberland, sent in by Mr. W. F. Davidson for determination was photographed and showed similar variations from the conichalcite pattern. Qualitative spectrographic comparison of the Mapimi and Brandy Gill materials with several conichalcites suggested that the differences in the powder photographs might be due to the presence of lead in the former.

The tholeiite of Kinkell (11 km. north of Glasgow G.P.O.) was described by the first author (Walker, 1930) and an analysis of its residual glass was given in a later publication (Walker, 1935). Since unaltered and separable residual glasses of basaltic rocks are rare, the Kinkell example has been referred to frequently in petrological literature. E. A. Vincent (1950) has made a detailed comparison between the Kinkell glass and a similar one from a tholeiite from Kap Daussy, east Greenland. In view of this and of the important part played by such glasses in discussions on basaltic differentiation, all the major constituents of the Kinkell rock have been isolated and analysed chemically and spectrographically. They are described below together with a fuller account of the field relations of the rock and some comments upon the significance of the new data.

Garnets rich in manganese and iron, associated with bariumfelspars, have been reported by de Villiers from the manganese ores of Otjosondu, South-West Africa, in which they occur as the most abundant silicate mineral. The farm Otjosondu is 80 miles NE. of Okahandja, a railway station on the line between Windhoek and Walvis.

One specimen (referred to as no. 1), of which de Villiers published a chemical analysis, is massive and of a somewhat dark-yellowish colour. The material is traversed by veinlets of hyalophane (Cn9), about 0.5 mm. broad.

Pargas in Finland and MansjSand and Tennberg in Sweden are the only three Fennoscandian contact metamorphic limestone occurrences of which systematic accounts have been published; in the first case by A. Laitakari (1) and in the two latter ones by the present author (2, 3). A more complete analytical programme would have been desirable, and unfortunately many of the analyses are incomplete, especially as regards the determination of the valency of the iron. Nevertheless, the available data, and a few I have been able to add later, may suffice to give us a general idea of the paragenetical and chemical differences between these Archaean mineral parageneses and those of much younger age which occur in connexion with the limestone masses associated with the alkaline occurrence of Alnö in Sweden.

The optical accessories here described are two dichroscopes to facilitate microscopical comparisons by eye between the hues and intensities of axial absorption colours shown by thin slices, crushed fragments, or detrital grains of transparent coloured doubly-refracting crystals. Their chief applications lie in microscopic mineralogy and petrology, but they can be of service, also, in chemistry and allied subjects.

The aims of the accessories are two in number. They provide: (i) simple microscopic means for viewing simultaneously any pair of distinct hues, intensities of hue, or combinations of these variables, which result from differential absorption of white light; and (ii) a convenient method for detecting small differences between any pair of hues, intensities, or both, in terms of immediate ocular comparison between two sets of small symmetrically-shaped coloured images which alternate, and meet in straight boundaries.

In mid-1949 the London Natural History Society set up a committee to investigate and record temporary geological sections in the London area. Among the earliest to be dealt with was the excavation in flood-plain gravel for the foundations of the Concert Hall for the Festival of Britain (1951). Samples of 100-200 grams were taken from two sandlentieles for heavy mineral investigation, and material from one of these, passing 60 mesh and washed by laevigation, yielded, on separation by means of a bromoform-benzene mixture of density about 2"73, an assemblage with abundant garnet, tourmaline, zircon, and kyanite, very occasional staurolite, cassiterite, and fluorite, and moderately abundant collophane.

X-ray powder photographs reveal thomsonite a.s the principal product of some low-temperature hydrothermal experiments. Glasses of three compositions were used as starting materials; one of tile composition of anorthite (CaAl2Si2O8), one of a gallium-containing anorthite (Ca4[Ga3Al5]Si8O32) in which 3/8 of the Al is replaced by Ga, and a glass of the oxide composition of zoisite minus the water (4CaO. 3Al2O3. 6SiO2).

The writer has recently been engaged in the investigation of a 'Lewisian' inlier within the Moine series of Glen Dessarry, at the head of Loch Arkaig, Inverness-shire. The inlier is largely composed of a series of hornblendic and felspathic gneisses but includes small lenses of marble and calc-silicate rocks. All these are to be reported later in two separate communications. There are in addition, however, some steeply inclined and impersistent ribs of mica-schist, granulite, and diopside-epidote-rocks, which will only be incidentally mentioned in those accounts in so far as they bear upon certain specific problems. In themsclves they are apparently of little petrographic interest except for the occurrence of an unusual copper-bearing recta-sediment. This it seems convenient to record in a separate note.