The granite mass of Dorback in the Braes of Abernethy, a few miles east of the village of Tomintoul, occupies an area of from 5 to 6 square miles, the plutonic rocks outcropping through the siliceous schists and granulites of the Central Highlands of Scotland. For a highland district the exposures are rather poor, since the igneous rocks only rarely appear from under a thick covering of peat and glacial drift, but towards the eastern margin of the mass the complex is well exposed in the valleys trenched by the Allt Iomadaidh and tributary streams. Here the interest of the plutonic rocks is twofold, for they form a complex of acid, intermediate, and basic types exhibiting considerable variation in petrography, and they include a series of xenoliths of quartzite, schist, and limestone which range from a few inches in diameter to a great mass of limestone 1½ miles in length. This xenolith has been mapped by the Geological Survey of Scotland, and it was the occurrence of a contact between limestone and plutonic rocks at this locality that led to the investigations of the authors.

In the early days of the study of glaciation the problem appeared to be a simple one: we are used to an ice-bound North Pole, and it was natural to assume that the boundary for some reason spread southwards to cover Scandinavia, Scotland, and even some of England. When it was further learnt that North America showed signs of extensive glaciation, this news fell naturally into place and scientists began to form hypotheses to account for a worldwide refrigeration. Quite soon, however, investigators in the countries concerned began to disagree as to the phases, and even the number, of glaciations: the centre of dispersal of the Scandinavian ice was found to be near the head of the Gulf of Bothnia; English geologists were inclined to favour only one glaciation, with certain retreats and advances; Boule would allow three glaciations, while Penck and Bruckner in their classical work on the Alps proved four in their region; Günz, Mindel, Riss, and Würm (with a short climatic improvement at the maximum); followed by the Bühl advance, Gschnitz Stadium and Daun readvance. But these Alpine phases cannot be followed into Italy. Gortani says (1): “Among us, too, Penck had disciples; and we, too, sought all means of adapting his system to the observed facts. But all attempts are vain because (a) nowhere are Günzian moraines to be found; (b) nowhere are to be found traces of more than one true interglacial with a warm climate and (c) the last two advances of the glaciers, where they have left separable traces, show themselves as two principal phases of one glaciation of medium intensity.”

Between the Cruachan Granite complex and the Glen Strae fault, to the south-east, and the Pass of Brander fault, to the south-west, there is a strip of Dalradian rocks (Fig. 1). These all lie within 1 in. Sheet 45 (Scot.) of the Geological Survey and are described in the Oban and Dalmally Memoir (Hill, 1908, pp. 19–28; Kynaston, 1908, pp. 38–40). Bailey has later distinguished the three great structural divisions into which he has divided the South-West Highlands. These are, in ascending structural succession: the Ballapel Foundation, represented south-east of the granite by Eilde Flags, Glencoe Quartzite, Leven Schists, and Ballachulish Limestone, and south-west of the same by Leven Schists; the Iltay Nappe, represented in both these positions by Islay Quartzite and Easdale Slates; and the Loch Awe Nappe, represented south of the granite by Ardrishaig Phyllites (Bailey, 1922).

A comparison of the chemical features of Scottish magmas, has been greatly simplified through the appearance of a recent memoir, compiled from the records of the Geological Survey (Guppy, 1931). This memoir gives the composition, age, locality, and microscopic petrography of a great number of Scottish rocks. The present note deals with three Scottish magmas: Devonian (Lower Old Red Sandstone), Carboniferous and Tertiary. It excludes certain analyses of the Survey list, owing to decomposition of the analysed material. It includes a few from outside sources, to augment the data concerning the Devonian magma (F. Walker, 1924, 1925, 1927, 1928; and J. G. C. Anderson, 1935).

The trachytes of Mont Dore were described, in the early days of microscopic petrography, by A. von Lasaulx; and they have since been noticed, in conjunction with other trachytes of the Auvergne, in papers by Fouqué, Lévy and Lacroix, and Dickson and Holland.

During the past year excavations have been continued in the deposits filling the channel cut through the Coombe Rock of post-Early Mousterian (Levalloisian) age and situated between Northfleet and Swanscombe. “The floor” at the base of the succession has continued to yield a fine series of contemporary Middle Mousterian (Levalloisian) implements, together with artifacts derived from the Coombe Rock and earlier deposits. Associated with the implements are the remains of Elephas primigenius, Rhinoceros antiquitatis, Microtus arvalis, M. anglicus, and M. nivalis.

The description of new sections of the junction between Cambrian and Pre-Cambrian rocks in Messrs. Boons quarry by Dr. Wills and Mr. Shotton in the November, 1934, issue of the Geological Magazine is of exceptional interest to me. I discovered the grano-phyric rock in 1932 and along with it the peculiar microdiorite which they describe, and have included description of both rocks and an analysis of the granophyre in a thesis recently submitted to London University.