The collection of rocks from the Sahara to be discussed was made by Captain D. R. G. Cameron, of the Royal Scots, during a journey across the Sahara from Kano to Algeria. The journey is described by Captain Cameron in his book A Saharan Venture (1928) and in a paper published in the Geographical Journal (lxxi, 1928, 538–59). The specimens were not collected in situ, which reduces their value somewhat. When one considers, however, that the collecting area is desert country where outcrops are comparatively scarce it is apparent that conclusions based on pebbles are not without value.

During the summer of 1928 I spent a month making a detailed study of the metamorphic condition of the rocks in the magnificent section displayed along the Banffshire coast and in the immediate hinterland, and this work has been supplemented by examination of a number of rock slices cut from specimens then obtained, and also of those in the collection of the Sedgwick Museum mostly collected by Mr. Harker.

IN the neighbourhood of Haddo House, between Methlick and Ellon, some 20 miles north of Aberdeen, there is a considerable body of gabbro that has been named the Haddo Mass. This intrusion is later than the general metamorphism of the Dalradian country-rocks and, from its resemblance to certain dated intrusions, earlier than the local Middle Old Red Sandstone. It belongs, therefore, to the Younger Gabbro portion of the Post-Movement Phase in the igneous history of North-East Scotland.

(1) The blocks of limestone in the Bowland Shales of School Share include a variety of rock-types of northern (Yoredale) facies and come from several beds near the Orionastraea Band of the Upper Viséan.

(2) They are a local accumulation at the local base of the Namurian (Upper Bowland Shales; zone of Eutnorphoceras pseudobilingue, E1 and rest, with evidence of some slight erosion, on one of the highest horizons of the Viséan (Lower Bowland Shales; zone of Goniatites spiralis, P2). Their horizon, therefore, is that of the mid-Carboniferous unconformity of Settle and elsewhere.

(3) They mark a comparatively small faunal hiatus (between the newsomi-meslerianum level immediately below and the C. malhamense level above).

(4) Their separation from the parent rocks and their assemblage are not due to tectonic causes. On the other hand, their great size points to some unusual form of transport.

(5) As they occur in a shale series near the Craven Faults they may legitimately be explained as the result of land-slips down s muddy slope from a limestone cliff, probably a fault-scarp raised by the mid-Carboniferous earth-movement.

(6) The circumstances recall those attending the Lower Palaeozoic conglomerates of Quebec. A recent explanation ascribes these to landslips caused by earthquakes from submarine fault-scarps. The School Share landslip may well have been caused by earthquakes, and the scarp from which the blocks were derived may have been essentially submarine.

The salt of Jebel Usdum is not a product of the Pleistocene Dead Sea, nor of the lake which preceded it (in ? Pliocene time), the waters of which were fresh for a long period and deposited sediments, with a maximum thickness of 1,000 feet or more, which are younger than the salt.

From the conclusions regarding the formation of complex pegmatites from the field and microscopic evidence, the following sequence of events is suggested:—

Towards the end of the solidification of a granite magma a liquid remains, having the general composition of a common pegmatite, but with small quantities of sodium and some rarer elements. By squeezing during crystallization this magma is separated into two distinct parts, one of which forms common aplite dykes. The other, more aqueous portion, when tapped by fissures, solidifies more slowly to form dykes, sills, or stringers of common pegmatite. During this solidification the albite (in solution), together with rare elements and their compounds, is concentrated in the remaining liquid portion, which now contains a very high proportion of water. This aqueous solution begins to migrate up the dykes or sills of common pegmatite, possibly even before the latter has completely solidified, showing a preference for the foot-wall, and begins to replace the earlier minerals, The first stage is the replacement of potash felspar, either microcline or orthoclase, by albite. Later there is a replacement of albite and sometimes of earlier minerals by spodumene, lepidolite, cassiterite, tantalite, etc. Cassiterite, possibly due to being carried in combination with a volatile element tends to be deposited in the uppermost part of the dyke or sill, where, however, some albite replacement has always preceded it.

In the paper by Dr. G. D. Osborne upon “Contact Metamorphism and Related Phenomena in the neighbourhood of Marulan, N.S.W.”, which appeared in the July number of the Geological Magazine, the sentence on page 305, line 23, beginning “It must be remembered . . .” should have read:—

It must be remembered in dealing with the present, or any analogous case, that lowering of temperature in the magma follows its intrusion, with resulting crystallization, which is accompanied by endothermic reactions in the aureole.

Among the recent additions to the collections of the Geological Department of the British Museum are two small consignments of fragmentary bones and teeth from the Directors of the Geological Surveys of Nyasaland and Tanganyika Territory. They are badly weathered, but, even though generic identification is alone possible, remains of fossil mammals from these areas reach Europe so seldom that the genera represented are worth placing on record.

Until the last few years the Asiatic Continent has yielded remarkably few remains of Dinosaurs. The recent discoveries in Mongolia have revolutionized our knowledge of their distribution in Northern Asia, and now much new information has come to light from collections made from the Cretaceous rocks of India.

In a recent number of the Records of the Geological Survey of India, vol. lxii, p. 410, Dr. Fermor has done me the honour to draw attention to a paper of mine (Geological Magazine, 1903, p. 305) in which I came to the conclusion that the thrust-plane at the base of the Himalayas must have, at its outcrop, a dip of about 14°; and he points out that this estimate agrees with the observations of Mr. Middlemiss in Jammu Province. My estimate was based upon a simple geometrical deduction which proceeds directly and inevitably from the assumption that the Himalayas rest upon a plane thrust-surface.