To account for a type of rhythmic unit found in the Bushveld complex of South Africa and probably in other layered intrusions, a hypothesis is put forward dependent on the different powers of crystal nucleation from supersaturated magma. It is suggested, for example, that the three common primary precipitate minerals, chromite, bronzite, and bytownite nucleated in this order which is probably dependent on the differing complexity of their crystal structures and that the common rhythmic unit, beginning with chromitite, passing upwards into bronzitite and ending with a bytownite-rich rock is the result of these crystals accumulating successively at the bottom'of the liquid.

The Whin Sill of this district has the form of a series of sills at different stratigraphical levels. Minor scarps at right angles to the main trend of the sill are explained by intrusion of offshoots, from its upper surface, along low angled fractures in the superincumbent strata. An intrusion mechanism is suggested to account for the presence of the Oxford Limestone both above and below the Whin Sill.

The composite sill of Rudh' an Eireannaich, Skye, is composed of basalt and felsite with narrow hybrid zones between them. The petrography of the rocks is described, accompanied by some chemical and spectrographic data.

In East Norfolk, boreholes have revealed the presence of a northern and a southern clay bed in the Crag. These lie at different horizons and have been linked to clay exposures previously correlated with the Chillesford Beds of Suffolk. It is concluded that a clay facies is developed at two main horizons in the Crag in Norfolk.

Minor folds in the Gramscatho Beds at the mouth of the Helford River have two predominant trends: W.S.W.-E.N.E., and N.W.-S.E. Main folds on W.S.W.-E.N.E. axes and cross folds on N.W.-S.E. axes have sub-parallel apical planes and occur in alternate zones which trend N.E.-S.W., parallel to the strike of the cleavage. The relations between the two systems of folding suggest that they are virtually synchronous.

It is concluded that the style of folding can be explained by a unidirectional regional stress acting normal to the apical planes of the folds.

Six new genera of terebratellacean brachiopods are proposed; one Triassic, one Jurassic, and four Cretaceous.

An account is given of the history of the term “eucrite”. It is shown to be very varied and hence has been a source of confusion to authors wishing to employ the word with precision, and to readers trying to understand its exact meaning. Because of the lack of agreement over the interpretation of this word, the author proposes that its use should be discontinued and the term “gabbro” utilized in its place.

Field evidence and theoretical arguments are used to elucidate the form of the intrusion. In the absence of a more accurate term this is described as chonolithic. Passive injection of the magma into a potential vacuum has enabled control to be exercised on the intrusion-form by the country rocks and their structures. The effects of this control are discussed.

Since my account (1937) of the structure of a part of Cornwall and O Devon, I have re-examined in particular the area known as Roseland between the Dodman and Porthallow at the eastern end of the Lizard Boundary. This has led to a re-interpretation of the structure which, though in part concerned with the Gramscatho Beds, applies to a large area of Cornwall and Devon. In the last few years many workers have appeared in the area and I have been frequently asked for my views on the structure and succession. It is evident that my 1937 paper has given rise to some misconception regarding these views, and it is desirable to place on record a brief summary of the main conclusions to which I have been led by my work during the last twenty years (mainly since 1951).

The current theories dealing with the mechanics of joint development are discussed critically. An analysis of the stress conditions which can exist in competent rocks in the crust is presented. The conclusion is reached that “Master” and “Regional” Joints can be, generically, either “tensional” or “shear” structures. They are, however, post-tectonic phenomena which develop as a result of uplift. Joints form a part of “movement pictures” because their orientation is determined by residual stresses. Reasons are given which indicate that the mechanism described is generally applicable to joint development in folded sediments, igneous rocks, and also to incompetent material.

The first systematic descriptions of the nosean phonolite of the Wolf Rock were given by Allport (Geol. Mag., 1871, p. 247; 1874, p. 462). Later a fuller account of the rock was provided by Teall in his British Petrography (1888, pp. 367–368). Since that time the rock has been repeatedly figured in text-books of petrography and in the light of two chemical analyses provided by J. A. Phillips (in Allport, 1871), regarded as a type example of a more sodic phonolite chemically comparable with the plutonic mariupolite. In view of the early date of these analyses, Mr. J. H. Scoon has at my request carried out a new analysis of the fresh rock, the results of which are provided in Table 1 (No. 1). This analysis reveals significant differences from the original, particularly in the potash content and shows that the rock is to be compared with the well-known phonolite of Brüx, Bohemia (Table 1, No. 3), and a phonolite from Colfax Co., New Mexico (Table 1, No. 2). The trace element distribution in the Wolf Rock has also been kindly determined for me by Dr. S. R. Nockolds (Table 1). Some additional mineralogical data which re-examination of the rock has provided may now be set down.

A north-south valley west of the Malverns contains a variety of Pleistocene deposits, largely hidden by late Pleistocene solifluxion. Around Eastnor is a stony clay attributed to an ice-tongue that crossed the Malvern Hills from the Severn valley. Various sediments north of Eastnor are thought to have been laid down in a lake held up by this ice-tongue and fed by a stream diverted across the hills north of the Malverns by the main Severn valley glacier. The Upleadon Gravels south of Eastnor are attributed to water released from the lake when the ice-tongue melted. Both lake and glacier are correlated with the Woolridge Gravels and hence with the Penultimate Glaciation.

New discoveries have established the presence of nine ammonite zones in the Middle Jurassic beds of East Greenland. The top two are Lower Callovian; the remaining seven yield ammonites unknown from extra-Boreal provinces and are presumed to range down through the Bathonian, possibly into the Bajocian.