The Llanrwst Pb–Zn and Llanfair–Talhaiarn Cu–Pb–Zn orefields contain vein mineralization similar to Lower Palaeozoic-hosted base metal deposits elsewhere in the British Isles, which are believed to have formed in the late Palaeozoic. K–Ar and Rb–Sr data on intensely sericitized wallrock material indicate that the main phase of mineralization at both orefields occurred between the mid-Devonian and theTournasian (386–350 Ma). The latest veins at Llanrwst formed in Visean–Westphalian times. Gangue mineral Sr isotope compositions indicate a mixture of radiogenic wallrock-derived Sr with less radiogenic Sr, with a poorly-defined trend to more radiogenic compositions with time.

The age of the main mineralization precludes dewatering of Carboniferous basins as a source of ore fluid. More generally Sr isotopes rule out unmodified basinal brines or metamorphic fluids as mineralizing agents, since their Sr content would be too radiogenic. Local sources of unradiogenic Sr are available at Llanrwst in metadolerites and calcareous sandstones and at Llanfair–Talhaiarn in thin Ludlow Limestone beds.

Last summer Miss D. L. Reynolds kindly organized an excursion of ten, all told, to discuss her recent paper on “The Eastern End of the Newry Igneous Complex”(Quart. Journ. Geol. Soc., xc, 1934, p. 585). We were introduced in most helpful fashion to both field exposures and microscope slices. In some particulars, differences of interpretation arose; and at the conclusion I circulated a brief memorandum. This by request I now offer, with trifling changes, for publication. Page and figure references, unless otherwise defined, apply to Miss Reynolds's paper.

Rhombic pyroxene as a constituent of thermally altered sediments has hitherto been recorded only from a few contact zones, and, as the conditions under which it is generated in metamorphosed sediments are of some interest, these may be examined.

Elhuyar, born in Spain in 1755, received a thorough training in mining geology at several of the leading European mining schools. He was appointed to an important post in New Spain (Mexico), where he arrived in 1788. There he devoted himself to reorganizing the administration of the mining industry and then to founding a School of Mines in Mexico City. This was opened in 1792, and in 1811 moved into the magnificent new building known as El Palacio de Minería, which now houses the Engineering School of the University. When an independent government was set up in Mexico in 1821, Elhuyar returned to Spain, where he continued to work for the government as a mining consultant. He prepared a report on the Rio Tinto mines and was responsible for the planning of the School of Mining Engineering in Madrid.

Amongst the rocks whose original structures have been more or less deformed by metamorpbic agencies the geologist very commonly meets with curious eye-like inclusions of mineral matter, which are generally known by the name of augen. Close investigation of a large series of rocks exhibiting these eyes brings to light the fact that under this name are classed two essentially different kinds of structure. in the one, the kernels or eyes are manifestly the unsheared portions of the rock, whose sheared portions constitute the schist that envelops the eyes. in the other kind of augen structure the eyes consist of crystalline minerals, whose development as such is shewn to be posterior to the shearing to which the matrix has been reduced, by the fact that the eyes of crystalline matter have not participated in the shearing, but are bright and generally unfractured throughout.

Dr. J. R. Sutton has recently read a most important paper to the Royal Society of South Africa on the diurnal variation of level at Kimberley. The paper gave the preliminary results of observations made during the course of three years upon the variation of the level of the ground as recorded by a large horizontal pendulum of a special design made for the author by the Cambridge Instrument Company. It appeared from the results that the movements in the surface of the ground, which set up corresponding movements in the pendulum, were very great. The maximum westerly elongation of the extremity of the pendulum occurred about 5.30 a.m., the maximum easterly about 4.15 p.m., the medium positions a little before 11 a.m. and 9.30 p.m. Geometrically these movements may be represented on the hypothesis that the hemisphere facing the sun bulges out, forming a sort of meniscus to the geosphere. The rise and fall of the surface of the ground which such a supposition would postulate is enormous, and the very magnitude has led Dr. Sutton to hesitate in giving the figures. There can, however, be very little doubt that some rise and fall in the earth's surface is occasioned by the sun's gravitational pull, although the present figures may have to be lessened by taking into consideration other causes which contribute to the disturbance of the pendulum.

It would be the safer plan, in considering the remarkable Gravel and Crag deposits which characterize so distinctly the Quaternary Period, to infer the size of rivers, amount of rainfall, and elevation of tides from the deposits themselves. Further acquaintance with meteorological phenomena may find a fitting explanation of the difficulties we meet with in explaining the position of the gravel at such heights above our present streams, and fresh-water, alternating with marine clay, and sands at such depths below the sea-level.

The appearance of Professor Bonney's letter in the December a Number of the Geological Magazine, inwhich he suggests that Mr. J. J. Harris Teall's proposed explanation of the cause of the foliation of the Lizard gabbro “ought to be regarded as an hypothesis on its probation, and should not be quoted as an undoubted fact,” emboldens me to offer some remarks on the subject.

At the southern end of Thorney Island, about three miles S.S.W. of Emsworth, in West Sussex, there are low cliffs of London Clay covered by Pleistocene deposits. The London Clay has been folded near the top, and its surface presents a series of basin-like depressions, 3 to 10 feet in diameter, and evidently caused by downward pressure. These basins are occupied by Pleistocene gravel, which contains numerous erratics—many of igneous rocks—and resembles the better-known Erratic Gravel of Selsey. The Erratic Gravel is covered by Coombe Rock and Brickearth, which form the top of the cliff, as shown in the diagram.

In his fourth paper Mr. Geikie sweeps the entire Glacial series of the Eastern side of England into correlation, not only with the Scotch Till, but with the Boulder-clay, both Upper and Lower, of the North-west of England. This he does, so far as I follow him, without any other grounds than that there are beds of “gravel, sand, mud and clay” in the Scotch Till. It is impossible, within the compass of these remarks, adequately to contest Mr. Geikie's views; but if the evidence of organie remains is to be regarded as worth anything, such a correlation cannot, I contend, be maintained.

Few students of Geology can doubt that the elevation of the Weald has been the most important factor concerned in determining the present surface-geology of the south-east of England. It has been constantly before my own mind in all my studies of Tertiary Geology for the last ten years, as the problem to the solution of which many other preliminary questions required answers. In my first paper on Tertiary Geology, read before the Geologists' Association in 1883, I pointed out that the presence of Eocene pebble-beds in the Woolwich and Reading series and in the Bagshot series afforded strong evidence of the encroachment of the sea upon the Upper Chalk in Eocene times. This conclusion is accepted by our greatest authority on Tertiary Geology, Prof. Prestwicb. The fact alone furnishes a strong presumption that the elevation of the Weald had commenced before the close of the Eocene period; while the many outliers of the Woolwich and Reading beds at high altitudes on the N. Downs, taken along with the general absence of the London Clay there, seems to tell us that the initial elevation of the Weald hill-range had gone far enough for this to form a shore to the area of deposition of the London Clay. I have shown further, in a former volume of the Geol. Mag., that, though there is no absolute proof, there are grounds for believing, that certain outliers of sands on the N. Downs (at Chipstead, Headley, and north of Netley Heath) are more likely to turn out to be of Upper Eocene age, than of any age to which they had been hitherto assigned by different writers.

Many attempts to revive and improve the classification of our rock-groups have been made from time to time, and the International Geological Congress will doubtless make a further effort in the same direction.

A well preserved specimen 46mm. long and 22·5mm. wide (Fig.17) was found by Mr. R. Cory near Catadupa. The body whorl is contracted below the suture and has ten varices which die away at the anterior contraction and are slightly acute at the shoulder; the anterior part of the shell has five wavy spiral ridges. A smaller and more delicate but poorly preserved form (Fig. 18), with similar but more anteriorly produced varices, occurs just above the Barrettia limestone at St. Ann's Great River and resembles specimens of L. crassicostata Stol. from Assam figured by Spengler (Pal. Ind., N. Series, vol. viii, mem. i, 1923, pl. iii, figs. 34a, and b). Another species of Lyria or Volutilites (Fig. 16) with elongated spire has about 7 coarse uneven varices on the body whorl and occurs as badly preserved casts in the Providence shales. It attains a length of 47 mm.