The confusion that has arisen over the interpretation of the D2—D3 boundary is analysed and a new definitive section of the Upper D Beds is given.

An attempt has been made to show that basic magma is associated with vertical and not with folding movement, that basic intrusions take the form of those characteristic of unfolded regions and of relatively high levels and that differentiation in situ is common.

It is argued that basic magma is emplaced in the orogenic belts as flows and typically non-orogenic intrusions during the geosynclinal or sinking phase of the orogenic cycle, that rocks of the appinitic suite, which commonly occur as stocks associated with granodiorites, are formed from these non-orogenic basic rocks by a process of hybridization during a subsequent folding phase, but that no further basic magma is introduced during this phase.

It is suggested that the terms Non-orogenic Association and Orogenic Association might replace Volcanic Association and Plutonic Association to indicate the relation of basic and acid magmas to their tectonic environment.

The lophophores of spire-bearing fossil brachiopods (Spiriferoidea and Atrypoidea) arereconstructed by homological comparison with living brachiopods. It is inferred that all spiral brachidia supported simple spiral lophophores. For each type of brachidium, only one arrangement of the spirolophe could have created an efficient filter-feeding system. The water would have entered the mantle cavity laterally and been ejected medially; but would have been filtered between the whorls of the conical spiralia either outwards (e.g. Atrypa) or inwards (e.g. Spirifer). These are the only possible alternatives: it is probable that both systems were evolved more than once.

Metamorphosed limestones carrying tilleyite are described from the northern slopes of Glen Dibidil, Isle of Rhum.

The well-known Carboniferous cyclothems of North America and Europe are discussed as examples to illustrate the great extent and lateral variation of sedimentary cycles. Very many other instances of cyclic sedimentation, in rocks of most ages, in many parts of the world, are also characterized by a more or less regular lateral migration of simultaneously existing depositional environments, caused by repeated transgressions and regressions of the sea over an epicontinental platform. Theories of varying complexity which have sought to explain cyclic sedimentation are briefly summarized, and it is suggested that the two basic requirements are a slowly subsiding sedimentary basin and more or less regular eustatic changes of sea level. The former will decide the geographical location. The latter could be a natural, periodic and world-wide consequence of the combination of the continuous effects of sedimentation and sostatic or orogenic movements of the sea floor.

Crop markings reveal a polygonal network resembling that of “patterned ground” in arctic Alaska. From this the former presence of perennially frozen ground is inferred, with the implication that the mean annual isotherm of this part of Worcestershire was at least 13½° C. lower than it is at present. It is argued that this condition obtained at the period of the Irish Sea Glaciation maximum.

Comparison of streaked-out “ripples” formed by the drag effects of a current passing over a watery, yet cohesive sediment bottom with convoluted laminae formed within beds of fine-grained sandstone suggests a common origin. Application of Bagnold's recent discoveries on the behaviour of cohesionless sediment in flowing fluids to the problem results in a modification of Kuenen's hypothesis of origin of the convolutions. According to the new interpretation, convolutions arise when formerly cohesionless sand grains become cohesive after deposition and respond to increased shearing due to higher current velocity by a décollementtype of adjustment with the plane or planes of adjustment located within, or in some cases at or below the base of the growing sandstone bed. Convolute “anticlines” in cohesive sand are thought to serve the same function as that played by current ripple-marks in cohesionless sand, i.e., they create additional bottom relief in order to increase the drag and restore equilibrium to the added shearing stress imposed by the current that cannot be counterbalanced by grain-to-grain encounters.

Laboratory measurements of the effect of a confining pressure on the strength and stress-strain characteristics of a metallurgical coking coal are described. Several-fold increases in the strength, the Young's modulus and the elastic strain at failure were found as the confining pressure was increased to 5,000 lb./n.2. The results are discussed in relation to various criteria of failure. It was found that failure was represented by Coulomb's equation relating shear stress and normal stress, provided the observed angles of fracture were not influenced by local edge stress concentrations.

Geological studies in eastern Singhbhum and critical analysis of Dunn's published work in surrounding regions suggest that during the Archaean times a volcanic geanticlinal arc, now represented by the Dalma lavas, tuffs and agglomerates extended roughly east–west for more than 150 miles. The geosynclinal trough in the southern, concave side of the arc was filled with argillaceous sediments, thin subgraywackes and orthoquartzites derived from a land mass to the south. The trough in the northern, convex side of the arc was filled with a huge thickness of argillaceous sediments associated with graywackes, siliceous limestones, sandstones and pre-orogenic ultra-basic and basic intrusives. Both the troughs near their border with the volcanic arc were filled with pyroclastic materials.

During orogenic movements two anticlinoria were formed in the supracrustal sediments above the two troughs separated by a syncline above the geanticline, with a granulite-migmatite core in the heart of the outer geosyncline.