During the years 1918–1931, there were 270 earthquakes with unusually deep foci, 167 in the Northern Hemisphere, 101 in the Southern, and two with epicentres on the equator. The normal depth of focus is assumed to be about 50 km. or ·008 of the earth's radius. The focal depths of the above earthquakes range from ·005 to ·090 of the earth's radius below the normal depth, or from 50 to 380 miles beneath the surface. Throughout this paper, the depth, when given in terms of the earth's radius, is referred to the normal depth; when given in miles, to the surface of the earth.

Since the publication in 1887 of Dr. H. B. Guppy's book (1) very little has appeared on the geology of the Solomon Islands, and Cowper Reed's book (2) of 1921 is based on Guppy for this area. During the last four years a small representative collection of rocks has been sent to the British Museum (Natural History) and examined by Mr. W. Campbell Smith, to whom the author is much indebted for their identification.

Following the original suggestion of Searles Wood, the Norwich Brickearth has been referred to the same phase of glaciation as the Basement clay of Holderness, which in turn has been correlated with the Scandinavian Drift of Durham. Recent work by Stather (1929) and by Bisat (1932, 1935) shows, however, that the Basement clay of previous authors (Wood, Lamplugh, Reid, and others) may be resolved into a drift (a) of Scandinavianorigin, together with (b) deposits of separate derivation; and the time now seems appropriate for a critical examination of the position of the Norwich Brickearth in the glacial sequence.

During the course of the John Murray Expedition some 22,000 miles of the floor of the Arabian Sea and the neighbouring areas of the Indian Ocean were mapped by means of the Echosounding apparatus. The region between India and Africa was crossed four times, namely:

(i) from Aden to Karachi,

(ii) from Bombay to Mombasa,

(iii) from Zanzibar to Colombo, and

(iv) from Colombo to Aden,

while more detailed surveys were carried out in the Gulf of Aden, the Gulf of Oman, and the region off Zanzibar.

Evidence from Mull and Ardnamurchan is brought forward to show that the injection of cone-sheets is accompanied by a vertical lifting of the upper wall. This confirms Anderson's explanation. It is argued that the fracturing and injection are of a quite sudden character and that it is in the nature of the process that no evidence from recent volcanoes has yet been obtained of contemporary cone-sheet injection.

Recent work in the Glen Falloch area has revealed that certain small masses shown as diorite on 1 inch Sheet 46 of the Geological Survey (Scotland) contain rocks belonging to the kentallenite and appinite suites. As these intrusions have not been previously mentioned in geological literature it has been considered worth while placing a short description on record.

A Remarkable little fossil fish, Eucenturus paradoxus, was described by Traquair (1905) from a single specimen from the Calciferous Sandstone Series of Ardross, Fifeshire. Traquair's description is as follows: “This extraordinary little organism measures 2⅜ inches in length, of which ½ inch may be allotted to the head, and ¾ inch to the body, and 1⅛ inch to the tail. The head is a mass of calcareous matter, in which something suggestive of a broad curved mandible can be seen, but admits of no further description. The body, ⅜ inch broad in front, is composed of a greyish film, which, when examined by a strong lens, is seen to consist entirely of minute, slender, slightly-curved and sharp-pointed spinelets. The tail is tapering in form, consisting of amorphouslookingcalcareous matter, but on each side (assuming that the creature is crushed vertically) is a conspicuous row of double spinelets arranged exactly opposite each other. From a common base arise two spinelets, which are placed close together, and nearly parallel to each other; one of them, the anterior, being only half the length of the posterior one, which just behind the body may attain a length of 1/16 inch, though towards the end of the tail they become smaller; both spinelets are slender, slightly curved, round in transverse section, smooth externally, sharply pointed, and traversed internally by a central tubular pulp cavity. No trace either of internal skeleton, or of limbs, or of fins of any sort can be seen.”

The forces which produced the folds of the Alps, and caused waves of compression to be transmitted as far as the Weald, may have been sufficiently powerful to start a drift displacement of Europe towards the north-east. As there does not appear to have been any similar compression in North America, a north-easterly movement of Europe would have caused shear in the strong continental layers which are considered to have connected the two continents. Tensile stresses would probably have arisen in these layers, unless the layers had begun to thin out before the state of tension was reached. There would have been a limit to the extent to which thinning could have proceeded, since a certain thickness of rock would have been needed to produce the necessary stress-differences. This thinning out process may have come into operation, except in a number of kilometres immediately below the surface, where tensile stresses may have arisen as drift continued. Under these circumstances the uppermost part of the crust would have sagged upon the thinning region, nd been broken up by a system of tension fractures.

The peculiar tectonic structure called “boudinage” by Lohest (5, pp. 471–2), has recently been found in Unst, Shetland Islands, by Professor H. H. Read (8, pp. 134–8), who has also noted its occurrence in tie Durn Hill quartzites of Banffshire (9, p. 471).What would now be termed boudinage-structure was seen by Ramsay in North Wales, and was described in 1866 in these words (6, and. fig. 18): “In the great quarry west of the Ffestiniog and Trawsfynydd fault the cleavage dips from 45° to 50° north-west, the inclination of the beds being about 35° in the same direction, and a greenstone dyke runs through them between the cleavage-planes…, bulging and thinning off in a rapid succession of oval-shaped masses of 3 or 4 feet in length. Associated with it are quartz veins ccurring principally at the points between the separate bulgings of the greenstone.”

Sandstone “dykes” have not previously been noted in Tanganyika Territory. Those described below were observed by the writer while engaged in regional mapping in the Dodoma district during 1936.

One of the most widely quoted but least common Chalk ammonites is Ammonites navicularis Mantell, which has been the subject of a very careful paper by the late G. C. Crick. Judging by the literature, however, this species is still generally misunderstood, and inquiries from correspondents are partly responsible for the present note. There is no doubt that widely different forms have been included in A. navicularis, from Sowerby's time (1827) down to the present (e.g. Collignon, 1931), and I have on previous occasions separated, with new names certain forms wrongly attributed to this species by Sharpe (1857), Guéranger (1867), and de Grossouvre (1912). But although a good deal remains to be done, without figuring typical specimens and without having material for comparison from India, Portugal, and Madagascar, it is not advisable to express opinions on the ammonites figured as A. navicularis by yet other authors, e.g. Stoliczka (1865), Choffat (1898), or Boule Lemoine, and Thévenin (1907).