SOME recent studies on the periodicity of earthquakes have thrown light on their origin and especially on that of their attendant after-shocks. The periods that are of most service for this purpose are the solar periods of one year and one day, the lunar periods of 29·6 and 14·8 days, and the period of 42 minutes due to the throbbing of the earth in consequence of the crustal displacement that gives rise to the earthquake. As a rule, the maximum epoch of the annual period falls either in midwinter or in midsummer, that of the diurnal period about midnight or noon, that of the period of 29·6 days close to the times of either new and full moon, that of the period of 14·8 days at or about the times of new and full moon or of first and last quarter, and that of the 42 minute period either with the return movements after their passage to the antipodes and back or half-way between these returns.

It is proposed in this communication to describe the results obtained, and methods employed, in an investigation of the British strand-line oscillations and to discuss related episodes on the Continent. The original object was to determine the nature of the movements and, if possible, to discover their time relations, but the unexpected correlations that emerged rendered it necessary to extend the scope of the investigation. The data available include the pre-Glacial, 100-ft. and 25-ft. raised beaches together with the knowledge that the land stood high above the prevailing sea-level and was glaciated between the first and second beaches mentioned, and that there was a re-advance of the ice between the second and third. The most interesting feature of the oscillations is that they constitute a complete cycle; for the sea which left the pre-Glacial beach at the beginning of Quaternary time, practically returned to it at the close. This cyclic nature of the movements suggested that if the first, or determining, movement could correctly be assumed, it should be possible to depict the changing relations of sea and land in a simple bi-axial diagram; the movements being given absolute value by reference to the earth’s centre.

The following notes refer to a collection of rock specimens made by the late Capt. T. Alex. Barns, F.R.G.S. Along with a summary of the geology of the four main islands in the Gulf of Guinea by the late Prof. J. W. Gregory it was intended to publish them as an appendix to a travel book by Capt. Barns. This book was never published as Capt. Barns was killed at Chicago in a motor accident on the 5th March, 1930. He had, however, already published an account of his journeys in the Geographical Journal. Prof. Gregory's manuscript on the geology of the islands cannot now be found. It is felt, however, that the petrographical notes and the two new chemical analyses that accompany them, should be placed on record.

Among interesting finds at Hook Head are several specimens of a species of Blastoid with the brachioles in position. A few also have part of the column attached. The species has not yet been worked out, but it probably belongs to the genus Orophocrinus. The calices are mostly crushed and for that reason may be difficult to identify, but so far as a somewhat cursory examination has shown they belong to a species similar to O. pentangularis Miller. Blastoids in this condition do not seem to have been recorded from European rocks before. In the Catalogue of the Blastoidea in the Geological Department of the British Museum, published in 1886, Etheridge and Carpenter state on p. 63 that no traces of brachioles have been discovered in any European Blastoid. I do not know of any record since. They are rarely found in this state of preservation even in America, so it seems worth while placing the specimens on record now. Dr. L. B. Smyth records Orophocrinus pentangularis Miller from the Upper Michelinia antiqua Beds at Hook Head, also a Blastoid from the Upper Michelinia favosa Beds, but he informs me he has never seen any of these organisms in the above state of preservation before. Our specimens occurred on a thin shaly layer on top of a limestone in the Supra-dolomite Beds at Doornoge Bay. Like ours, the specimens recorded by Dr. Smyth also have calices which are mainly flattened, so I was interested to find in the Austin Collection in the Liverpool Museum several specimens which are fairly round and solid. Over thirty specimens are labelled from Hook Head. This corresponds with the names in the MS. catalogue which are given as Pentremites pentangularis, P. acutus, P. oblongus, and P. enniskilleni. The last named is also given in the catalogue from Co. Fermanagh.

A few miles to the west of, and running approximately parallel to, the main Rhodesian Railway from Kimberley and the Cape, there is a well defined line of hills, which is the eastern edge, and forms the scarp face of, the Kaap Plateau. Between this plateau and the railway is a belt of flat low-lying ground through which the Great Harts River runs southwards to the Vaal. In the vicinity of Taungs Station, between Warrenton and Vryburg, the scarp line is running nearly due north and south, and is only four to five miles distant from the railway; followed southwards it gets farther away from the railway and assumes a more south-westerly course. The Kaap Plateau is formed of dolomite of the Campbell Rand Series of the Transvaal System, corresponding to the dolomite in the Transvaal. The formation dips gently to the west at angles of 2–3°. Along the escarpment the dolomite rests conformably on dolomite shales, the latter frequently forming a series of terraces from the base of the plateau upwards. Lying unconformably against the dolomite to the east are the Lower Karroo Beds, which are largely concealed by secondary limestone and the recent alluvium of the Harts River basin.

In a previous communication (1) it was shown that a temporary lowering of ocean-level, of the order of 1,000 metres, served not only to elucidate the nature of the British Quaternary strand line oscillations, but was also competent to explain the climatic changes that occurred during that period over a region that extended from North-West Europe to the pluviated lands south of the Mediterranean. It was also pointed out that a change in ocean-level of such magnitude must, being world-wide in extent, have recorded its effects in distant regions. There should, therefore, be a wide choice of areas where the hypothesis might be subjected to a critical and possibly decisive test.

New loop-ways on the Great Western Railway to by-pass stations at Westbury and Frome have recently provided complete sections of Corallian Beds and Cornbrash.

THE plateau-lavas of Antrim cover an area of approximately 1,550 square miles—the largest area of Tertiary lavas in the British Isles. Although from the earliest daysof geological science these lavas have attracted many observers, very little has been done in the way of petrological study and, curiously enough, the dominant olivine-basalt lava has never been analysed.

In a preliminary article (1) dealing with the British Quaternary strand-line oscillations it was shown that unexpected correlations had emerged as a result of the methods employed. Of the possible assumptions the only one to prove workable was that there had been, during Quaternary time, a temporary lowering of ocean level of 1,000 metres or more. The graphs left no reasonable doubt that if the ocean level had moved in the way assumed the Mindel-Kiss interval of Penck's Alpine sequence must be equated with the major glaciation of North-West Europe and the British Isles. In order to test this, the only assumption made, it was applied to the coral reef problem (2) and there it was successful in offering what should be an acceptable solution. It was surprising to find that Darwin had actually used an apparent rise of ocean level, of the same order of magnitude, to illustrate his own theory of subsiding islands. The success of the postulate when faced with the coral reef problem was held to have invested it with a high degree of probability. It was pointed out, however, that changes in ocean level of that magnitude could best be explained by the sinking of the ocean floor, and the North Pacific Ocean was indicated as the probable position. The cause of the changes of ocean level will now be investigated and then its consequences discussed in the light of ascertained facts.

From the standpoint of biological geography, the most significant event in the recent history of Canada has been the occurrence of widespread severe glaciation. This resulted in the whole of the previously existing fauna being either exterminated or driven southward. When the ice sheets receded northwards at the end of the last glacial period, this region was once more populated by animals, including both fresh water and terrestrial mollusca, the remains of which are to be found in various post-glacial deposits. The migration of animals into this new territory did not take place all at once, and it is noteworthy that no fossil mollusca have been found in the deposits laid down during the early stages of the glacial retreat. The purpose of this paper is to give in concise form the history of the present molluscan fauna of this region in so far as it is evidenced by the post-glacial fossils found in the region. The series of fossil-bearing deposits herein described is far from complete, and many additional finds will doubtless be made in the course offuture field work. Nevertheless, a sufficient number of observations has been made to indicate the general nature and duration of the molluscan immigration into the area.

The structure of the earth was supposed by Suess to be tripartite, there was an outer layer of rocks mainly granitic, the sal, or sial as it is usually now called. This rested, or “floated”, on a dense layer called the sima, of basaltic character, within which was the earth’s core, or nife, metallic in nature. Such a simple conception has been modified in the light of later knowledge: geologically there is much evidence pointing to the existence of several shells of increasing density within the crust. This is to some extent supported by the evidence of seismology, the layers below the upper sedimentary layer being the Granitic, the Intermediate (of tachylyte or diorite) and Lower Layers (dunite, peridotite, or eclogite) (1). According to the latest information there are four layers intermediate between the granitic and lower layers: the thickness of the sedimentary layer varies from about 2 to 6 kilometres in mountainous regions: the thickness of the granitic layer varies, being about 10 to 12 kilometres in Central Europe. In low-lying regions the total thickness of these two layers is probably about 6 kilometres less than in mountainous regions: “the thicknesses of the other layers are very difficult to determine; the upper two probably have together a thickness of about 15 kilometres, but the others can hardly be determined from the observations” (2).

The years that followed the Great War saw a rapid development in knowledge of the graptolitic faunas of the Eastern Alps. Professor M. Gortani described many graptolites from the Carnic Alps, and papers from the Geological Department of the University of Graz dealt with the same subject, as well as the distribution of the graptolites over a wider area of the Eastern Alps. Especially noteworthy was the surprising discovery of graptolites in the so-called grauwacke zone of the Alps, which follows the southern margin of the Northern Calcareous Alps. In the grauwacke zone, which consists of Palaeozoic and more ancient strata, more or less metamorphosed, graptolites were found at the following localities, (a) Fieberbrunn in the Tyrol (1), where the zones of Monograptus cyphus to M. turriculatus are found, and the presence of M. priodon indicates that higher zones may occur; (b) environs of Eisenerz in Styria (2), where the zones of M. gregarius to M. griestoniensis are found, as well as the zone of M. nilssoni; (c) Montavon in Vorarl-berg (29), where a badly-preserved specimen of Monograptus, possibly M. priodon, was discovered.

The westward extension of the South Wales Coalfield in Pembrokeshire is of complicated structure and the sequence is very imperfectly known. This is particularly true of the west of the county, where the coalfield has been very little worked for many years. In the eastern portion of the county, between Haverfordwest and Carmarthen Bay, the Coal Measures consist mainly of shales which have been correlated with the Lower Coal Series of the main part of the South Wales Coalfield and which are not higher than the Pulchra Zone.

Diagnosis.—Shell small, thin, tapering more rapidly towards apex. Marginal grooves well developed, with raised rims between which there is a fine longitudinal furrow. Faces, flat to slightly concave, ornamented with strong transverse ridges, evenly distributed, narrower and less rounded than the interspaces, forming rounded angles of about 135° and also bending forward at lateral ends.

THE theories of earth-formation and earth-structure of which the seventeenth century was so prolific, are illustrated in the works of Woodward and Burnett, of Ray and Steno, and others who are usually cited when the history of geology is being discussed, but occasionally one meets with a cosmogony that seems to have remained unnoticed by subsequent writers. In such cases the neglect is, no doubt, to be attributed to the fact that some of the views put forward were too preposterous to command serious consideration even in days when speculation and credulity were more rife than observation and common sense: and if a book was not discussed by contemporary writers it would, in all probability soon join the limbo of things forgotten. This seems to have been the fate of a little pamphlet entitled The Anatomy of the Earth, written by Thomas Robinson, Rector of Ousby, in Cumberland, and “printed for J. Newton, at the Three Pigeons in Fleet Street” in 1694.

The following notes were made while on an expedition with Mr. J. T. Cunningham (financed by the Trustees of the Percy Sladen Trust and the Royal Society) to the Island of Marajó in the mouth of the River Amazon. The object of the expedition was not geological so that it was not possible to carry out an extended survey of the district explored.

There are many reasons for believing that the floor of the oceans, at least of the Pacific, consists of basaltic rocks as distinct from the granitic rocks which form the continents. It is here suggested that this non-uniform distribution of rocks over the earth’s surface may have been caused by the particular kind of cooling mechanism which was adopted in the early stages of the earth’s history. A stage would be reached when granite would separate out as a lighter mass resting on the heavier and still liquid viscous basalt.

The base of the Phillipsi Zone, which Professor Trueman has made the base of his Upper Westphalian, is taken at the horizon of the Shafton Marine Band in Yorkshire (1) 1 and in consequence the following beds are included in this zone:—

The epidiorite with which this note is concerned is exposed in a small overgrown quarry 50 yards north of St. Catherine’s old Chapel, Loch Fyne. The rock is soft and is easy to cut, and it is said that some was used in the building of Inveraray Castle.