A flora of cuticle fragments obtained by maceration of the Bathonian coal of Brora is described together with some lycopod megaspores from the shale below the coal. All the species are known from the Bajocian or Bathonian of N. Yorkshire. Ptero-phyllum cycadites sp. nov. is described as new, the type being a Yorkshire specimen. The formation of the Brora coal is discussed.

The traditional concept of contraction crack formation is based on a model having a regular arrangement of stress centres. A more realistic result is produced if the model consists of a close random packing of stress circles; this gives a crack configuration very close to that observed in real basalt flows.

Microscope studies of a flattened fold are consistent with conclusions from macroscopic observations that whereas mudstone cleavage development may have resulted from a laminar-type flow governed by competent confining sandstone beds, the sandstone cleavage appears to be related to the dilation of texture during the early stages of deformation. Continued deformation results in a textural disruption of the initially competent sandstone, which is considered to allow flattening.

The mylonitic character of the peridotites of St. Paul's Rocks on the Mid-Atlantic Ridge was reported in a contribution by the writer (Tilley, 1947), these ultrabasics then being referred to as dunite or peridotite mylonites. The available chemical analytical data were assembled in that paper and a new analysis provided of a two-pyroxene representative. The type carrying porphyroclastic amphibole was represented by an analysis by Washington (1930) but it was shown that this analysis erred in its alkali determination, and that the reported occurrence of jadeite could not be confirmed.

Six serpentinites occur in the Moinian granulites of the North-East Ox Mountains. Four have been known for some time and have been previously described. Additional information on these and the associated vermiculite deposits is provided. The remaining two serpentinites are described for the first time. A pyroxenite vein associated with one of these may have been produced by meta-morphic regeneration.

The relationship of some of these serpentinites to the probable position of the Highland Boundary Fracture-zone in Eire is also discussed. Brief comparison is made with serpentinites occurring in the Scottish Moinian.

Unusual single kink-band sets in calcareous slates are described and their mechanism of formation discussed. Regional inferences are drawn concerning Armorican strike-slip movements.

In an attempt to obtain information about garnet nucleation a series of eleven apparently homogeneous metamorphic rocks, from a small area near Mallaig, Inverness, Scotland, have been analysed to determine bulk chemical and modal compositions, garnet grain size and number of garnet crystals occurring in unit volume of rock (N). No correlation of N with any function of chemical and modal compositions could be found, and it is therefore concluded that, if the influence of trace components can be neglected, externally imposed factors (for example, time-temperature variation) or internal physical factors (for example, the surface area of the rock just prior to garnet formation) must exert a controlling influence on garnet nucleation. It was found, however, that in each specimen, there was a preferred crystal radius and the relative frequency of occurrence about this preferred value was constant for all samples studied. Preliminary comparison with other systems, investigated by the authors, suggested that the nature of this relationship may provide evidence of the conditions under which these rocks recrystallized.

The age of the Garabal Hill-Glen Fyne igneous complex has been determined as 392 ± 4 m.y., by the Rb-Sr method. The components of the complex had an average initial (87Sr/86Sr)0 isotope ratio of 0·705 ± 0·003. Geological contamination of marginal components is reflected in the (87Sr/86Sr)0 values of these rocks which were found to be ca. 0·710, significantly higher than values from uncontaminated samples. The results are in accord with the view that the individual members of the complex had a common source, comparable with regard to the Rb/Sr ratio, to the source of basalts. It is inferred that complete melting of such source material followed by magmatic differentiation is an appropriate mechanism of origin for the complex.

Distinct variations of the natural remanent magnetism in a section of volcanic rocks in Greaser Canyon, Lake County, Oregon, correlate with faulting inferred independently. The palaeomagnetic data is also consistent with the occurrence of a suspected diastem in the local volcanic sequence.