Three areas in peninsular India are described in which the geometric orientation of the drainage pattern has led to the location of a system of parallel crustal fractures. One area is in the Archaean basement of South India. The remainder are located on Deccan basalts. The fractures are not as a rule accompanied by fault displacements, and are regarded as planes of shearing. The shearing in the Deccan basalts cuts across the post-lava dykes, and is considered to coincide with late magmatic mineralization and the break-up of the Gondwana continent in mid-Tertiary times.

In the schistose grits of the Dalradian Series north of Stonehaven there is clear evidence of the deformation of the rock by shearing of the original quartz grains along planes roughly diagonal to the “flattening”, which here coincides generally with the schistosity of the quartz-schist, the final product of the metamorphism. As this corresponds essentially to the case studied by Schmidt and others, an examination of the rock fabric is made having in mind the mechanism suggested by Schmidt, and more fully elaborated by Anderson, to connect up crystal orientation with deformation. The results of the study do not indicate that the simple model of equal spheres, each with its set of glide planes, and all in cubical packing, is in any way adequate to explain the petrography of this quartz-schist and it is suggested that any theory that makes a purely mechanical reaction of the quartz grains to the deforming forces the dominant factor in the production of a new texture is at variance with the facts since there is clear evidence of the continued solution and crystallization of quartz throughout the whole of the metamorphic period.

In the Malin Head promontory an Older fold-system, with thrusting and folding about N.W.-trending axes, was followed by Caledonoid folding about N.E.-trending axes. The limbs of the Older folds, both major and minor, now lie in the sheet- dip of the Caledonoid folds, the dips of the Caledonoid limbs being equivalent to the plunges of the axes of the Older folds. Most of the S-planes are shared in common by the two fold-systems. The only exceptions are those that outline the closures and rising parts of the Older fold-system, and these form zones in which the S-planes strike at right angles to the Caledonoid trend. By reference to the outcrop-forms in the area described, and with the aid of plasticine models, it is demonstrated that the outcrop-forms of folded folds are readily recognjzable, and that they provide visible evidence of the approximate axial directions and relative ages of the two fold-systems. By comparative study of outcrop-forms on the models and structures seen in sections cut at right angles to each of the fold-axes, it is found that the structures differ radically from those constructed by projecting the outcrop-forms on planes normal to the axes. The “down-the-plunge” method of viewing a geological map thus provides no clue to the actual three-dimensional structure of folded folds.

The clay mineral, dickite, is a common rock-forming mineral of many Carboniferous sandstones in North Wales and Northern England and of Middle Jurassic sandstones over much of North-East Yorkshire. It occurs as well-shaped authigenic crystals associated with highly altered mineral assemblages, including partly dissolved feldspar which is one of the probable sources of the alumina and silica.

In the west of the Isle of Rhum (Inverness-shire), Tertiary acid rocks outcrop over an area of approximately 6 square miles. A core of spherulitic microgranite is surrounded by graphpphyre1 which, in turn, is bounded on the north by Torridonian Sandstone; although much of the boundary is marked by a low-angle reverse fault, part of the junction is undisturbed and a belt of transitional rocks, some 1,400 feet in width, intervenes between the graphophyre and the Torridonian Sandstone. The transitional rocks are divisible into five zones which are interpreted as marking successive stages in the conversion of sandstone into graphophyre. Evidence is presented indicating that the microgranite, into which the graphophyre grades inwards, represents a still more advanced stage of transformation.

The drainage pattern of North-West Scotland is considered in relation to already known and newly inferred fracture zones, and it is concluded that a system of Tertiary fractures, connected with the plutonic centres of the Western Isles, has been superimposed on the rhombic pattern of late-Caledonian faulting.

The pelitic hornfelses surrounding the Carn Chuinneag–Inchbae complex have, with the other rocks in the area, been subjected to the regional metamorphism which affected the Moine Series as a whole. The minerals of the original hornfelses have reacted to form assemblages which are typical of regional rather than purely thermal metamorphism although the massive structure of the hornfelses is well preserved.

By studying the changes which took place in the hornfelses during the regional metamorphism it has been possible to deduce the most likely mineral assemblages indigenous to the original hornfelses.

The results of the chemical analyses of some of the pelitic hornfelses are presented and chemical data on some of the garnets are given. It is considered unlikely that all the garnets in the hornfelses, which are essentially almandines, formed as a result of the earlier contact metamorphism: some at least probably occur as a result of the later regional metamorphism.

Alternating zones of normal and reverse natural permanent magnetization, each comprising about twenty-five flows, have been found in the Tertiary and Quaternary plateau basalt series of Iceland. The techniques for measuring this permanent magnetization are discussed and some results shown. It is suggested that zones of normal and reverse magnetization may be useful for correlation purposes in volcanic districts. Some other possible applications of rock magnetism are mentioned.

A small collection of non-marine lamellibranchs and plants from the Madumabisa Shales of the Gwembi district of Northern Rhodesia is described. It includes a new species of the genus Kidodia, Palaeomutela rhomboidalis, and P. neglecta, associated with Glossopteris indica. The Madumabisa Shales may be correlated with similar beds in Southern Rhodesia assigned to the Tapinocephalus zone of the South African Lower Beaufort Series, and are of Upper Permian age.

A graptolite fauna, found in cherty shales interbedded with volcanic rocks south of Charlestown, Co. Mayo, indicates an Arenig age.

A plea is made for the wider use of concise descriptive phrases instead of rock-names of the conventional type, which are usually uninformative. The writer's case is discussed in relation to the so-called “mugearites”.

The pegmatites of Trolvis Quarry, Carnmenellis, are small lenticular masses which were developed before the joints of the associated granite. Both mineralogically simple and complex types occur: the latter are drusy. Whilst the earlier minerals lining the druses may have crystallized in a closed system, the later minerals were clearly deposited from a moving phase. The disposition of the later minerals was largely determined by earlier crystals acting as baffles to the mineral-depositing agents. The pegmatites appear to occupy spaces formed by the solution of the granite by a pegmatitic fraction of the magma.

A complex of granitic, syenitic, and dioritic rocks forms the western part of the Insch mass. All these rocks appear to be related, but they are later than, and have no direct connection with, the basic rocks forming the bulk of the Insch mass. The granitic and syenitic varieties are fairly uniform, but the dioritic types are variable rocks rich in xenoliths which are apparently derived from basic rocks. It is suggested that the diorites were formed by contamination of the magma producing the granitic and syenitic rocks.

It is argued that the Strollamus outcrop of Tertiary basalt lavas reaching south to Coire Garbh occupies a volcanic inbreak or sink dating from the lava period; and that the Broadford Dolerite is not metamorphic.

The Permian in Durham is the most internally disturbed of the newer or covering beds of England. In deep borings it is a dark dolomitic rock full of sulphates and chlorides; at the surface it has quite a different appearance. The Permian and overlying Secondary beds seem to have been lowered by downwarping. During the subsequent differential uplift and denudation the area remained a land surface and the sulphates were removed by penetrating water, not by subaerial weathering. Horizontal and low angle thrusts occur in the Sunderland area above about the middle of the underlying Coal Measure basin. The movements may have been induced by diminution in rock volume following solution and segregation accompanied by attraction or packing together of the mass of the formation.

Ten clinopyroxenes have been investigated chemically and optically. Eight of these were separated from the rocks of the Garbh Eilean sill and two from other rocks relevant to this inquiry into the trend during crystallization of pyroxenes in minor basic intrusions of mildly alkaline and undersaturated type.

The remarkable xenolithic dyke described in this paper is one of the little-known swarm of camptonite and monchiquite dykes of probable Permian age in the Northern Highlands of Scotland. It is the first intrusion containing xenoliths of ultrabasic rock to be recorded from the Glenfinnan area, although such xenoliths have been described from vents or intrusions of probable or known Permian age in Caithness in the extreme north of Scotland, and in Ayrshire and elsewhere in the south of Scotland.

Four new solitary tetracoral genera and their type species from the Mississippian of Western Canada are described, named, and discussed. These new genera are part of several previously undescribed coral faunas from the northern Canadian Rocky Mountains.

The Quartz-dolerite intrusion of Sgùrr nam Meann, Ardnamurchan, is shown to be a ring-dyke which has sill apophyses extending from its outer wall. This is a form of intrusion which has not been recognized before, and its field relations are described in detail. The quartz-dolerite is extensively veined by acid rocks which are ubiquitous in all parts of the intrusion, and most abundant in the sills. From the evidence of the distribution and nature of the veining it is concluded that the acid and basic components of the intrusion must have been ernplaced simultaneously. It is suggested that a gas-charged, acid residual magma may have separated from a crystallizing basic parent under the influence of sudden reductions of external pressure acting upon the system.

Tear faults cutting the Barnesmore Granite in County Donegal are described. The Lough Belshade fault trends N.E.–S.W., and there has been a lateral movement along it in a left-handed or sinistral sense of 2·2 miles; it is believed to be of the same age as the Great Glen Fault. The Barnes Lough Fault crosses and displaces the Lough Belshade fracture, and may be, in part at least, Tertiary. Although the movement along it is much smaller, it has taken place in the opposite sense.