The application of the microscope to petrology made it possible to I investigate effectively the history of the foliated rocks and of metamorphism. This was done, as it happens, only a very few years before I began any special study of such rocks, so that the account, of my own work almost corresponds with that of the general progress in a knowledge of them. I was led, after some preliminary efforts, into investigating two distinct problems, each of which, as I soon discovered, presented rather exceptional difficulties. These were the pre-Carboniferous rocks of Charnwood Forest and the serpentines of the Lizard. The problem involved in the one was how far some of them were or had been igneous in origin, lavas, tuffs, and agglomerates, or were stratified rocks, which by pressure and mineral changes had been so altered as to be indistinguishable from some of the former. The other introduced the question of the origin of serpentine, about which in 1873 the utmost uncertainty existed. This, from its associations, led on to investigating the nature and origin of gneisses and schists, so that the history of my own studies during the last forty-five years happens to illustrate. some important aspects of the progress made during that period.

The hydraulic limestone series which cap the Silurian rocks of the New York sections, and are commonly embraced under the name “Salina Group”, are probably the richest known depository of remains of the Merostome Crustacea. During the past fifteen years we have been engaged upon the study of this fauna, and the results at which we arrived in our memoir on the Eurypterida of New York could not have been safely attained without the previous labours of Dr. Woodward and the late Professor Rupert Jones, of Huxley, and Hugh Miller for the British species; of Friedrich Schmidt, Nieszkowski, and Holm for the species of the Baltic basin.

A British Museum official may perhaps be pardoned if, in a review of the progress of mineralogy since the first appearance of the Geological Magazine, he begins with a reference to scientific work done in the Museum with which the Editor was so long associated. At the time when the Magazine first saw the light the Keeper of the Mineral Department was the late Professor Nevil Story-Maskelyne. He was one of the first to grasp that efficient tool for deciphering mineral aggregates which had been provided by Nicol and Sorby in the thin-section. He was engaged in the particular work to which Keepers of that Department have since appeared to consider they must in duty bound devote much of their time and energy, viz. the investigation of meteorites, and, assisted by the microscopic examination of thin slices of these bodies, he was soon able to announce the discovery in them of several new species, one of which, the sulphide of calcium, oldhamite, must have been formed under conditions very different from those which prevail on the earth's surface.

Amongst the Carboniferous corals, not the least interesting are those species which, for one reason or another, may be difficult to classify, or at any rate diverge somewhat from the common order. It is with one of these aberrant members that the present communication is concerned; and it is, perhaps, not altogether unfitting that most of the material happens to be of Irish origin.

In South Devon the outcrops of Middle Devonian igneous rocks form a series of roughly parallel bands, which broaden out and occupy a continuous area about twelve square miles in extent in the neighbourhood of Ashprington village. No detailed account of the petrological characters of these rocks has been given, although similar types have been described fully in the Plymouth Survey Memoir. For this reason, and also in the hope that further study might explain more completely the cause of the broadened outcrop, I investigated many exposures in the Ashprington area.

Trilobites in common with all other Arthropods shed their more or less rigid external covering or exoskeleton periodically. To accomplish this ecdysis it is necessary for this covering to split somewhere; and it is highly probable that the facial suture was the line along which such splitting took place. There seems, however, to be a tendency to assume that all lines which served this purpose are homologous. This has introduced unnecessary difficulties into the study of Trilobite classification. The object of this paper is to do something towards the elimination of this source of error.

The three genera (or generic terms) that serve for the title of this paper comprise a series of Cretaceous and Tertiary Echinoids which are morphologically similar, and, in consequence, systematically chaotic. Although the time is not yet ripe for an attempt to disentangle the nomenclature of the various genera and species from the knot in which it is involved (a condition not to be wondered at in view of the early description and variable qualities of the forms), it seems desirable to publish the following comments on the group, making use of current names for the examples quoted. Pyrina, Desmoulius, as Lambert has shown, is typified by P. pelrocoriensis, Desm., a species that might well pass for a young member of the Conulus series. Conulus, Leske, has for genotype C. albogalerus, Leske, and the forms to which that name is usually applied in this country seem sufficiently like the original figure to pass muster. The genotype of Echinonëus is of course E. cyclostomus, Leske, and there has never been serious confusion as to the application of the generic name.

It has been known for some considerable time that the highest beds of the Northumberland and Durham Coalfield lie approximately beneath the town of Sunderland. The great syncline of the Coalmeasures of this area is distinctly accentuated in North-East Durham, so that a secondary basin-like depression is formed, in the centre of which these high beds occur. Beneath Sunderland, -where the top layers also exist, the Carboniferous rocks are concealed by the overlying Permian strata, but at a place called Claxheugh on the Wear, about two miles west of Sunderland, the Coal-measures are exposed for a short distance on both the north and south banks of the river.

The strong shock of January 14, 1919, originated in a region from which earthquakes have been absent for many years, perhaps for several centuries, and its interest is therefore increased by the fact that it was a twin-earthquake, that is, one produced by a single generative eifort in two detached foci.

The “Isle” of Purbeek includes part of a heathy tract underlain by the Tertiary beds of the Hampshire Basin, a central ridge formed by the Chalk which rises abruptly from beneath those beds, and, in its southern part, a hilly region underlain by Wealden, Purbeck, Portland, and Kimmeridge strata, and terminated by bold cliffs. Each formation gives rise to characteristic features in the landscape, the Portland Stone especially forming a dominant escarpment and vertical sea-cliffs.

From time to time I have been given an opportunity to discuss in the Geological Magazine the question of the cause or causes of climatic variations. The subject is one of deep interest to the geologist. Even Lyell, in the first edition of his Principles of Geology, gave a good deal of space to it, but contented himself with merely pointing out that variations in the distribution of the land would lead to changes in the climate. He wisely limited himself to this aspect of the question, for, at that time, the directions of the winds in middle latitudes were not such as meteorological theory would have led us to expect.

During a visit to the limestone quarries at Caldon Low last September we had the good fortune to discover an interesting exposure of a quartzose conglomerate containing numerous fossils. The bed was exposed in a strong joint-face running approximately N.N.W. to S.S.E., at the northern extension of the quarry on the north-west flank of the Low, just beyond the mineral line of the North Staffordshire Railway. The altitude is about 900 feet O.D. The conglomerate apparently extended some little distance to the south-west before the opening of the quarry, as we ascertained that some 20 or 30 yards had been removed in gaining access to the limestone behind. It appears to extend for some distance round the flank of the Low towards the north-east.

At Christmas, 1917, I had the privilege, owing to the kindness of the Hon. Mr. W. W. Hornell, of a short visit into Southern Sikkim, during which I observed glacial striation at a lower level than has been previously recorded in the Himalaya. This occurrence is the more worthy of record since striated rock-surfaces are reported as scarce or absent from the Eastern Himalaya even at much higher levels. For courteous help and the use of the library of the Geological Survey of India I am indebted to Dr. H. H. Hayden, and references to some of the literature I owe to him and also to Mr. E. W. Vredenburg.

The Divisions of the Limestone—The Thrusting in South-East Northumberland and North-East Durham—The Breccias.

The formation of a new Government organization to foster and promote the interests of the Mining Industry of the United Kingdom has been recently proposed in two distinct quarters. The Coal Conservation Committee of the Ministry of Reconstruction, which issued its report (Cd. 9084) early in the past year, recommended the establishment of a Ministry of Mines and Minerals, to be presided over by a Minister with a seat in Parliament; while in a report to the Minister of Munitions, issued as a white paper (Cd. 1984) on November 15, Sir Lionel Phillips, late Controller of the Department for the development of Mineral Resources in the United Kingdom, favours the setting up of a Mines Department, to be attached to one of the existing great Departments of State.

It is scarcely necessary in this Magazine to insist upon the vital importance of potash, or upon the reasons which led to the former economic dependence of our own and many other countries on German resources. The shortage of potash, which arose as a direct consequence of the outbreak of war, became more and more accentuated until the latter part of 1917, when production from various revived and newly discovered sources began appreciably to relieve the then seriously acute position. In 1913, the last complete year of the older conditions, over £900,000 worth of potassium salts were imported from Germany by Great Britain, against imports of only half that value—much of which was cream-of-tartar, a byproduct of the wine industry—from all other countries. It is now safe to say that the German monopoly is completely broken, partly because of the return of Alsace to France, and partly because of the discovery of new deposits, and the successful development, under the stimulus of war conditions, of new methods of potash recovery from sources formerly unremunerative or unsuspected. The purpose of this article is to pass briefly in review the chief sources from which potash is, or may be, profitably extracted, other than those of the famous German deposits, which already have a voluminous and familiar, or at least readily accessible, literature.

It is these which afford the justification for any comparison between Sinocystis and Megacystis. Those of Sinocystis are, it will be remembered (antea, December, 1918, p. 534), a transversely elongale peristome, a hydropore-slit approximately parallel to the peristome, a gonopore to the left of the anal plane, and a hexagonal or pentagonal periproct. These openings, though differing in details, are in number and position essentially similar to those of Aristocystis. Hitherto there has been much uncertainty as to the positions, and even the presence, of the hydropore and gonopore in Megacystis. It will here be shown that both are present, and that all four openings have much the same relations as in Aristocystis and Sinocyatis, especially the latter.

A Careful examination of four fossil millipedes from the Middle Coal-measures of Sparth Bottoms, Rochdale, three preserved in the Manchester Museum and one in Mr. H. Howard's private collection, has revealed some striking features which seem to justify a re-description of the whole material.

A character of the suture-line that has received considerable attention lately is the obliquity with regard to the radius. Of course, it had long been noticed that suture-lines may vary in the form and foliation of their elements (brachyphyllic, dolichophyllic, and leptophyllic suture-lines of Mojsisovics, and euryphyllian and stenophyllian suture-lines of Haug) as in their general course. There maybe (externally) a strong convexity forward (Cyclololus), a straight (Sphenodiscus) or wavy line (Pseudosageceras), or a convexity backward (Protengonoceras). Again, the suture-line may be inclined strongly forward towards the umbilicus (Cheltonia) or have a retracted or dependent inner portion (Psiloceras). It is this Litter obliquity that has been used as a generic and even family distinction, e.g. by Mr. Buckman, to determine the affinity of Bredya with Hammatoceratidse, and not Hildoceratidæ.

It will be recalled that to the list of theories relating to the origin of flint Liesegang has added another, namely, that the flint is due to the rhythmic precipitation of a silica solution diffusing through the Chalk. Cole in an admirable essay has made this view accessible to English readers, and at the same time somewhat expanded the original suggestion. Yet little by way of evidence is offered beyond a certain plausibility in the idea, and its undoubted competence to explain better than any other hypothesis yet suggested the remarkably regular recurrence of flint lines. When reading over the chief Cretaceous literature with this problem in mind, there seemed to me to be a not inconsiderable body of fact lending support to this view. Accordingly the object of this paper is to examine existing data in the light of Liesegang's suggestion in order to see whether or not it may be regarded as a reasonable working hypothesis.