Some time before the war I examined the profiles, or longitudinal sections, of several rivers, with the object of ascertaining whether they tended towards any particular curve. The method of examination was similar to that employed by Professor O. T. Jones in his interesting paper on “The Upper Towy Drainage System”, but the data were obtained from maps and were not so exact as his. Some rivers showed a very close approximation to a catenary for the greater part of their course, but this was not the case with all. My final conclusion was that there is no general curve towards which all river-profiles tend the form is influenced by the rate at which the volume of the river increases downwards. No sufficient data, however, were available in the case of any river for the exact application of a general theory which was in my mind, and such approximations as were possible were too rough to be of any real value.

It has generally been held that the family Encrinuridae contains the four genera Encrinurus, Cybele, Cromus, and Dindymene, though Cromus is sometimes regarded as only a sub-genus of Encrinurus. The distinctive features of Encrinurus and Cybele as usually understood have been described and discussed by many authors, especially Salter, Nieszkowski, and Schmidt, but in 1877, Woodward considered Cybele to be only a sub-genus of Encrinurus. Dindymene is sufficiently distinct from the others to have had generic rank always accorded to it.

Dr. C. G. S. Sandberg's article on the origin of the Dwyka Conglomerate calls for a wider publicity of the facts connected with the early establishment of the glacial origin of that deposit. The general history of the matter is given in the Geology of South Africa, by Drs. Hatch and Corstorphine, second ed., p. 14. The original determination was made by Dr. P. C. Sutherland in his Geology of Natal, Pietermaritzburg, 1868, but a number of geologists discussed it subsequently, such as C. L. Griesbach, E. J. Dunn, A. G. Bain, R. N. Rubidge, A. Moulle, G. W. Stow, R. Pinchin, A. R. Sawyer, G. A. F. Molengraaff, A. Schenck, and A. Stapff. Among the diversity of opinions expressed it was difficult to arrive at any definite conclusion at that time. In September, 1895, Dr. R. Marloth submitted to a meeting of the South African Philosophical Society a number of boulders which he thought showed glacial striations, but the evidence was not considered satisfactory by Dr. Corstorphine or myself, the only two geologists in the country.

As reported in the Geological Magazine, Vol. LX, 1923, p. 432, fossiliferous Carboniferous rocks were discovered by Messrs. C. Barrington Brown and R. A. Baldry in the Amotape Mountains of North-Western Peru, and their collection (comprising Cephalopoda, Lamellibranchia, Gasteropoda, Brachiopoda, Polyzoa, Crinoidea, etc.) presented to the Sedgwick Museum, Cambridge. This was augmented in 1924 by the presentation of a further collection made during a new visit to the area. In addition to the kindness of the two field investigators in allowing this fauna to he examined by the author, the latter wishes to acknowledge his indebtedness to Mr. C. Barrington Brown for drawing most of the figures.

In the summer of 1915 I had occasion to visit some of the oilfields of the Western Caucasus, with the view of locating new oil-wells. During my study of the geology of the petroliferous areas on the northern slope of the Caucasus I was able to ride to the Shugo crater, the easternmost of the mud-volcanoes of the Taman peninsula. This crater is situated on the watershed between the Shugo and Chekups Rivers, about five miles south-west of the village Varen-nikovsk. From a distance, as I rode uphill from the wide, alluvial plain of the Kuban River, the picturesque and well-wooded foothills did not disclose any semblance of a mud-volcano, but on climbing the southern slope of the hill, a most unsuspected and striking view was suddenly revealed. Here at my feet lay a nearly perfect crater, about ¾ mile in diameter (Pl. XXI, Fig. 1).

The object of this paper is to give a connected account of the small plutonic masses which pierce the Lower Palaeozoic strata of South-East Scotland. These intrusions have been overshadowed by their larger neighbours the Galloway Granites, of which Teall has given such admirable descriptions, but are worthy of more attention than they have received in the past.

When studying the geology of the Giants Causeway district in 1924 I noticed a strange system of well-developed joints on the surface of some basalt columns. As these only appeared on the planes of a few columns in this district, where several hundred thousand basalt columns are exposed, and as these joints were only to be found on and quite close to the surface, I firstly regarded them as a mere feature of weathering. It was only after Professor Dr. Maximilian Weber in Munich pointed out to me the striking resemblance of these joints to the photos published in Daubrée's Études synthétiques de Géologie Experimentale, and I decided to investigate this problem closer, the results of which are given as follows:–

This system of joints is only to be found at one locality in the Giants Causeway district, i.e. the lower parts (sea level) of the “Grand Causeway” (west side) opposite the “wishing chair” (the spot is marked with a white X on Fig. 1, Pl. XIV).

Lough neagh is one of the numerous lakes possessing a few species, either identical with or differing but slightly from true marine forms living in the present seas. The idiots of Lough Neagh are the pollan, Coregonus pollan, and the shrimp, Mysis relicta (a near relative of the marine Mysis oculata). They have been described by Dr. R., F. Scharff and Professor W. Dakin and Miss M. Latarchie.

One of us has described these deposits in two papers read before the Geological Society (Q.J.G.S.), vol. lxxv, 1919, p. 204; vol. lxxxii, 1926, p. 101.

Reference has been made in previous articles (1, 2) to the discovery of fossil fishes in the sandstone immediately overlying the basal conglomerate of the Keuper near Nottingham. The upper portion of this sandstone splits into slabs two or three inches thick along filmy partings of greenish clay. The specimen described and figured below was found lying upon the surface of one of these slabs with its head partially buried in the sandstone itself. After being carefully cleaned it proved to be a well-preserved specimen of Semionotus differing to a sufficiently marked degree from previously described species to merit the creation of a new species.

To reopen a question which has seemed definitely settled ever since 1898, and which has accordingly become an accepted opinion in geological circles, is neither a pleasant nor an enviable task. Yet, as the question is one of universal interest geologically, it has to be tackled and settled. In the following I intend to discuss the problem in a manner as objective and concise as possible, in order to concentrate the argument on the points which fundamentally govern the problem. As, from personal observations on the spot I am only familiar with the South African occurrence, I intend discussing that one only, however likely it be that the arguments brought forward may fundamentally affect the appreciation of other similar occurrences in South America and Asia.

The Plate which accompanies this article, showing till over-riding and overthrusting in its readvance the gravels on which the yard of Harvard University is built, is of a temporary exposure. This was made in putting in a large apartment house at the north-west corner of Arlington Street and Massachusetts Avenue, North Cambridge. The camera was pointed north. Realizing its ususal character, I got my colleague, Prefessor M. S. Munro, who is a virtuoso with the camera, to take it, and have used it as a postcard to friends. One of them, my old teacher, William Morris Davis, said it was unexcelled, and urged its publication. That is the occasion of this article, for, when I came to think of it, to obtain such a photograph required an unusual combination of circumstances:—

(1) The artificial excavation;

(2) A strike that suspended work at the critical time (it is an ill wind that blows no one good);

(3) Just such conditions of wind and drying out as to bring out the different beds in the sands. The coarser ones dry and crumble more rapidly, while the fine hold the dampness and stand out. We might add:—

(4) A man living on the street (myself) to appreciate it, and

(5) A friend who is an excellent photographer.

In September, 1926, accompanied by my friend, Mr. James Begg, of Glasgow, I spent a few days in the Clitheroe district, being attracted thereto by a perusal of that excellent paper by Dr. Parkinson on this region (Q.J.G.S., vol. lxxxii, 1926, pp. 188–249). The paper itself, with its interesting details, really fanned into flame a smouldering desire to examine the district further, since over twenty-five years ago I had read in Our Common British Fossils, by the late Dr. Taylor—a fascinating book to a young geologist—the statement that in the neighbourhood of Clitheroe. whole beds are composed of crinoid heads. Being in Lancashire shortly afterwards, I one day went to Clitheroe and spent a few hours in Salt Hill Quarry, but owing to ignorance of the localities and lack of experience in crinoid collecting, I was grievously disappointed so far as these fossils were concerned. When Mr. Begg and I visited the district in 1926 I recognized the landmarks and saw at once that if I had gone further east to Bellman Quarry I should probably have been amply rewarded. On the results of our 1926 visit Mr. Begg and I were well pleased. We explored most of the knolls and quarries of the district and spent a considerable time, especially at Bellman and Coplow Quarries, where we collected a large number of well-fcpreserved crinoids.

In the first part of this paper an account has been given of the heavy minerals of the northern part of the Leinster Granite and of the contiguous rocks in the Ballycorus district.

From the southern shores of Dublin Bay there stretches to the south-west a broad granite intrusion with rocks of supposed Ordovician age on both sides of it. These rocks are metamorphosed near the granite, and the belt of metamorphism is wider on the south-east than on the north-west side, indicating, no doubt, that the plane of junction dips more steeply on the latter side. Near Dublin the Lower Carboniferous rocks rest unaltered upon the granite. On the south-east side, in the northern part of the county of Wicklow, the belt of Ordovician rocks is only some 2 miles wide, and a large area of supposed Cambrian rocks lies between it and the sea. Around the hill of Carrickgollogan a. patch of similar rocks appears incongruously in the middle of the Ordovician belt. After a study of the region to the south of Dublin one seems to be naturally drawn towards this small area around Carrickgollogan, for it presents a problem, the key to which may explain the geological structure of a much wider area.