The object of this investigation was to examine the well-known Hestercombe “syenite” in greater detail than had been done before, to attempt to trace its extent, and if possible, to determine its age.

The three masses of Dirrington Great Law, Dirrington Little Law, and Blacksmill Hill consist of riebeckite felsite, closely allied to the rock of the neighbouring Eildon Hills and most probably contemporaneous with it, i.e. they are of a Carboniferous age. They may represent the denuded remains of a laccolith which has been intruded into upper Old Red Sandstone conglomerates. The fourth mass forming Kyleshill is an orthophyre, with which is associated an andesite. The relations of these two rocks are obscure, and they may, or may not be, of the same age as the other three masses.

—The field impression of a high degree of uniformity in the composition of the intrusive Karroo dolerites over a vast area is confirmed by new chemical and microscopical studies. The pyroxene characteristic of the dolerites is a typical pigeonite, which, however, does not display any twinning on (100). The plagioclase is potash-free, usually a labradorite, but it has been observed that a homogeneous crystal of plagioclase may be in twin position to another homogeneous crystal of a very differently composed plagioclase. The close resemblance of the doleritic liquid to the artificial liquid taken by Bowen to represent basaltic liquid is noted, and his conclusion that pyroxene and feldspar should crystallize simultaneously in natural basaltic liquid is confirmed.

Conceivably the doleritic liquid was quite original and not a differentiate of any earlier liquid. However, analogies like those with the tholeiites and similar hypabyssal rocks of Great Britain suggest that in South Africa, as in Great Britain, the liquids of these hypabyssal rocks were derived from the slightly more femic plateau-basalt.

On that assumption the question of the mode of differentiation arises. The fractional crystallization of plateau-basalt, as now described by Bowen and other leaders, does not appear competent to explain the abnormally low soda of one of the analyzed dolerites, nor the excess of soda and total alkalies in plateau-basalt respectively over the soda and total alkalies of the Karroo dolerite. Further, the settling-out of early olivine does not explain the excess of (total) FeO in plateau-basalt over the (total) FeO in the Karroo dolerite. The actual relations indicate the need of renewed examination of the theory of magmatic differentiation by crystal-fractionation. In any case many more data are required before it is possible to decide upon the precise relation of the Karroo dolerite to a parental magma. Possibly such additions to knowledge may annul present difficulties in the way of accounting for the composition of the dolerite.

Before describing the section at Limpley Stoke I wish to acknowledge the very kind help given to me by Dr. W. D. Lang, F.R.S., Keeper of the Department of Geology in the British Museum (Natural History), who has had the fossils examined and through whose encouragement I am recording the results of an investigation extending over a considerable time.

The Tertiary beds cover the greater part of the island of Cyprus and their general distribution is shown in Bellamy's map published in 1905, while their characters and relations have been described with a certain amount of detail in Bellamy and Jukes-Browne's memoir on The Geology of Cyprus (1). Since then Philippson (37) has given a useful summary of our knowledge of the geology of the island with references to the literature up to the year 1918, and Cullis and Edge (38), though principally concerned with the igneous rocks, have more recently published a revised map with a summary of the Tertiary beds. But much work is still required before an adequate knowledge of them is obtained. The division into Eocene (Lapithos beds), Kythrean (Oligocene?), Idalian (Miocene) and Pliocene + Pleistocene Series as adopted in Bellamy's memoir, is convenient for a rough local classification of the beds. But the grouping of the Pliocene with the Pleistocene was obviously done owing to insufficient knowledge, and further subdivision of the series is undoubtedly necessary. Bellamy followed Gaudry (3) in regarding the Pliocene beds of the Carpas as representing an older stage than those of the central and southern districts. Russell (2) had previously recognized a lower series in the central valley which he called the Nicosia beds containing very abundant fossils, and an upper series which he termed the Kerynia Rock, comprising a yellow calcareous sandstone which furnishes most of the building stone in the island.

An average analysis is made of an altered intrusive greenstone occurring in the zone of the Kiruna greenstones with the special object of proving whether any local change of chemical composition is occasioned during the alteration processes by the uneven distribution of epidote, as was earlier supposed by the writer. The analysis confirms this, but it also shows that chemical inhomogenities must originally have occurred in the rock-mass. The relations found thus do not indicate great local changes of the chemical composition during the mineral alteration processes still less a change of the bulk composition of the rocks.

A comparison of a number of analyses of spilites and related An-richer rocks affords the following facts: among them there occurs a small group of An-rich members, which are designated here as diabases. Most of the analyses refer to rocks richer in albite, which are here called spilites in the proper sense. In the felspar diagram the projection points of the calculated felspar mixtures of spacing the rocks form a narrow zone close to the plagioclase line extending from 7 per cent An to 58 per cent An. As the dividing point between the diabases and the spilitic members a mixture with about 40 per cent An is accepted. When adding to the diagram the keratophyric rocks associated with the spilites, the whole distance from about 60 per cent of An to the immediate vicinity of the Ab-corner would be filled up.

Between the spilites and other rocks of equal femic composition and of about equal SiO2 content there exists in the felspar diagram an area in which very few rocks are represented. Petrographically the spilites are thus distinguished as a special rock-type. The boundary towards the ordinary basalts and diabases at the An-rich end of the series on account of the relations of the felspars alone is more dubious, as the individual basalts or diabases may be very poor in potash, but a difference seems to exist here also.

Other chemical qualities characteristic of the spilites are deficiency in alumina and high content of ferrous iron and of TiO2. The low percentage of Al2O3 is the main cause of the soda-rich composition of the felspar, as the CaO-content of the rocks is not low. The An-poor composition of the felspar in the rocks, furthermore, is accentuated by the entrance of An-molecules into the pyroxene during the crystallization of the magma, the generation of olivine being thereby prevented. This mineral, or pseudomorphs of it, is seldom recorded from the spilites. The high content of FeO is distinctive, not only for the spilites proper but also for the diabase members truly belonging to the series.

The importance of the high content of FeO for the course of crystallization in the An-poor members of the spilites is discussed. The consequence is found to be a change of the eutectic ratio of pyroxene and plagioclase contained in the concentration-diagram of plagioclase and pure MgO-pyroxene. The eutectic line for pyroxene and plagioclase during the crystallization of the magma will thus be reached earlier than shown by the diagram. In this way the textural relations of the rocks are explained without the hypothesis of autometamorphic changes and of an earlier An-rich plagioclase. In the appearance and mineral composition of the rock there is nothing compelling an assumption of this kind, unless the alteration of the minerals to compounds richer in water and carbon dioxide is referred to the period of consolidation. This would imply the fixing in the consolidated rock of these elements, but not a change of the other oxides. As to the time of the generation of the secondary minerals we do not know anything with certainty. The fact that the spilite group includes members which are poor in water and carbon dioxide, or are not decomposed at all, shows that a high content of these compounds is not necessarily inherent in the spilitic magma.

In 1928 the owner of the Tanjong Perak Rubber Estate, Dr. H. Trail Skae, noticed a white, porous, and friable rock near the Estate buildings and took specimens that were ultimately sent to the Geological Survey Department for report. The rock proved to be entirely new to British Malaya and of great interest, while in view of its complicated composition I suggested in a local publication that it should be called “Vitrite”. Dr. Skae registered the name “Vitrite” as a trade-mark for this rock, which has possible uses in commerce, but it has since been discovered that the word was used during the war by a Dutch firm for a particular kind of glass used in electrical work, so the name has to be abandoned, and the only attempt I have ever made to inflict a new name on petrologists has been signally defeated.

The area lying between the Lower Zambezi and its northern tributary the Lower Shire forms a relatively small salient between the better-known parts of Portuguese East Africa lying to the north and to the south, and a study of its geology in relation to that of the larger territory has yielded interesting results. The area described includes the southern end of the Nyasaland Protectorate and that part of Portuguese East Africa lying between it and the Zambezi.

In the literature of geology there is no book that has exercised a more lasting influence on the science than Lyell's Principles of Geology, the first volume of which was published a hundred years ago. The twelfth and last edition appeared in 1875, some months after the author's death. The active life of the work thus extended over some fifty or sixty years, while indirectly its influence still survives.

In an article with the foregoing title (Geol. Mag., Vol. LXVII, 1930, page 97) some unfortunate errors of statement, in part quite unaccountable, were printed.

The Cambridge Expedition to East Greenland in 1929 set sail from Aberdeen on 2nd July in the sealing-sloop Heimland, which had been chartered from Tromsö, Norway. Taking the Fair Isle passage, the edge of the pack-ice was reached six days later, and entered in the region of latitude 71° 30′ N., longitude 15° 30′ W. Last summer proved unusually difficult for navigation in the East Greenland ice-current, and it was not until 4th August after a month in the ice that we reached land-water and anchored in Mackenzie Bay. From the Bay a course was steered west-wards along Franz Josef Fjord to the foot of the Riddar Valley on the west side of Kjerulf Fjord. Here the party divided; the ship-party with two geologists during the next fortnight studied the tectonics shown in the great cliff-sections bounding Franz Josef Fjord and King Oscar Fjord (Davy Sound) and their branches (Fig. 1), while a second party of six was landed near Riddar Valley in order to map the tract of country lying immediately to the west of the head of Franz Josef Fjord (Fig. 2). Their ultimate objective was Petermann Peak, discovered by Payer and Copeland of the German Arctic Expedition of 1869–70, and estimated to be 11,000 feet high. A hurried reconnaissance in 1926 to the Cambridge Peaks had shown that the most likely route to the interior would be westwards along the watershed between the head of Kjerulf Fjord and the Nordenskiöld Glacier. The land-party left Kjerulf Fjord on 6th August, reached Petermann Peak on 15th August, and returned to base on 18th August. The present paper embodies the geological work carried out during the mountain journey, and is based on collections made by Mr. J. M. Wordie and Mr. V. E. Fuchs.

So much confusion has occurred in the past over the identification of the genera which we have been discussing, that a list of some figured species from the Jurassic rocks, arranged in their proper sub-genera, may be useful. The only previous attempt at a list of this sort, so far as I am aware, is that by Professor Rollier, who was only able to enumerate five species. He called all these Beushausenia, but two are not Beushausenias but true Parallelodons, while a third belongs to a different genus.

The compressed angustumbilicate oxycones of the Deiran and Raasayan stages of the Lower Lias are generally assumed to be “homoeomorphous terminals of different lineages” of the Arietidae. But while the characters of the adult sutures of these forms link them with that family, there is comparatively little evidence as to the details of the ontogenetic developments of the various genera hitherto recognized. It is the purpose of this paper to repair this deficiency in some slight measure. The two forms selected, partially for convenience, are of considerably different ages: Victoriceras is a Raasayan form, while Oxynoticeras oxynotum occurs at a considerably lower horizon in the Deiran.

The following observations are the result of working over the Middle Jurassic Arcidae with a view to monographic treatment of the Corallian and Bathonian species. The monographs must of necessity be slow in appearing, and in any case they are not the place to discuss the broader conclusions to which the investigations have led. The family is one full of interest from an evolutionary point of view, but an exceptionally involved maze of controversial matter, chiefly concerning nomenclature, by which the Arcidae have been burdened, has obscured the features of interest and the phylogeny.

The samples to be described in this paper were taken from a small bay on the north coast of Sutherland called Traigh Allt Chailgeag on the Ordnance map. This bay is about three miles east of Durness, and one mile west of the mouth of L. Eireboll. It is eroded in gneiss, and is fed by a small stream at either end of the bay.

A Study of stream action very soon shows that things are by no means so simple as they appear at first sight. Stream erosion is the basis of earth sculpture in temperate regions, except where direct differential weathering carves some of the details; yet its mechanism and the evolution of its topographical effects do not seem to be understood with any certainty. Even the classic discussions by G.K. Gilbert in his Geology of the Henry Mountains, and by W.M. Davis in his collected Geographical Essays, are, to the present writer at least, unconvincing at those points where the deductive structure is carried over, so to speak, to fit the work of actual streams, particularly with regard to the development of the curves of their longitudinal profiles. The parts given to this subject in the geological and geographical text-books are too short to allow a fully reasoned argument, but all appear to adopted the conclusions of Gilbert and Davis; though the line adopted in the present paper is to some extent approached by Chamberlin and Salisbury.

In Connemara and South Mayo, three main rock groups have been distinguished. The first group, largely developed in South Mayo (see sketch-map), consists of slates, phyllites, grits, conglomerates and thin limestones, and, although these rocks are much cleaved, sufficient fossils have been found to prove that they vary in age from Arenig to Ludlow. The second group of rocks, occurring principally in northern Connemara, consists essentially of quartzites, limestones and schists, and in this group fossils have not been found. In the pelitic schists of this group, biotite, garnet, staurolite and fibrous sillimanite are of widespread occurrence, proving that the group as a whole is in a state of medium to high grade regional metamorphism. We propose that the term Connemara Schists, which has previously only been used vaguely, should be restricted to this group. The third group, occurring in Southern Connemara, is a gneissic series which was tentatively correlated with the Lewisian Gneiss by early workers, and which is indeed remarkably similar to it in general appearance. Later work by Callaway (1887) and McHenry (1903) has, however, shown that these gneisses are not overlain unconformably by the Connemara schists, but are orthogneisses intrusive into them. Their age, therefore, relative to the Connemara Schists, is not in doubt.

Natural compact ice is not wholly crystalline. Salt solution is present in glacier ice at temperatures down to −21·72°, and is probably located at the intergranular boundaries. The proportion of brine is normally very small, but becomes considerable near 0°.

The special mechanical properties at the intergranular contacts, the “Hugi effect” on melting, the phenomena of regelation, and the infra-red absorption, indicate that the molecules at these contacts are in the amorphous state. This may be the case in ice free from salts.

Internal flow takes place by relative displacement of crystalline portions by means of slip:—

1. along the basal planes of the crystals,

2. along intergranular surfaces,

3. along fracture surfaces within the individual crystals.

Processes 2 and 3 are facilitated by the presence of liquid at the surfaces of slip, and it is the regelation power of this liquid which preserves the cohesion of the deformed masses.

The liquefaction at points of compression, transference of the liquid, and its congelation elsewhere, is an important factor in the formation of compact ice from névé, but is of secondary importance in the flow of compact ice.

The processes by which ice suffers deformation are those which operate in the flow of all crystalline masses, the comparative ease with which it is deformed being an instance of the weakness of rocks near their melting temperatures. Ice at hundreds of degrees below its melting point would compare in strength and hardness with the other crystalline rocks which exist under like temperature conditions in the outer part of the earth's crust.

There are two specimens of Bellerophon in the collection which may be co-specific—one is fairly well preserved, though a little distorted, and the other is worn.

One of the first features that will probably strike a geological observer in Jamaica is the extent and thickness of the great covering series of White Limestones. This series, which as Sawkins wrote in 1865, cannot be less than 2,000 feet in thickness, impresses one with the evident magnitude of the duration of the Tertiary period; especially when one reflects that it represents only a portion of the Tertiary, probably inclusively from the Upper Eocene to the Lower Miocene. Equally formidable though less conspicuous thicknesses of early Tertiary beds which underlie the White Limestones, namely, the Yellow Limestones and the Richmond beds or Carbonaceous Shale, represent the middle and basal Eocene.