The quantitative distribution of igneous rocks has recently assumed a place of importance in petrogenic discussions. This is due largely to the influence of Daly, who made a survey of the areal distribution of rock types as shown by their outcrops on published maps, and reached the well-known conclusion that intrusions are overwhelmingly granitic in composition, and that extrusions arc largely basaltic. If further research should firmly establish this result, it will unquestionably be a fact of the first order of importance of which any general theory of petrogenesis must take cognizance.

During the year 1919 specimens of some of the meteorites preserved in the Public Museum of King Willlam's Town, South Africa, were kindly placed by the Curator, the late Yr. F. A. O. Pyre, at the disposal of the writer for investigation. One of these specimens was a meteoric iron labelled Mount Ayliff, another a mass of oxidized material labelled Western Cape Province, and a third a small piece of iron labelled ‘found on Elandsburg at an altitude of 6,000 ft. in 1888’ Unfortunately Mr. Pyre was not in a position to supply very much more information about the specimens.

Rock-gypsum occurs as extensive deposits of considerable economic importance in the neighbourhood of Nottingham. The mode of occurrence and origin have been studied by several geologists, to whose work references were given in a recent communication to this Society. I Investigations have proceeded chiefly on field lines and microscopic examination has been somewhat neglected, except with respect to the contact relations of gypsum and anhydrite. Nevertheless, examination of thin slices from specimens collected in different parts of the district yields information of considerable interest and. it may be, of importance.

Dr. Harker has familiarized us with the use of variation diagrams, in which the Pereentage amounts of a constituent are plotted against the amount of silica present. He applied these diagrams chiefly to study selected rock groups, but also gave certain generalized eurves fo illustrate the chemical properties of his 'Atlantic' and 'Pacific' facies. Such variation diagrams based on an adequate body of analytical data form a useful means of constructing diagrams for the comparison of rock analyses. Some means of generalizing analyses becomes a necessity as their number accumulates and the labour of comparing individual analyses increases.

Among the lead and zinc minerals which occur in the Rhodesian Broken Hill mine workings at what used to be No. 1 Kopje (now represented by a hole in the ground) copper compounds are occasionally to be seen. Their quantity is always very small, but they are readily noticeable on accouut of their colour. They include malachite, chessylite, cuprite, copper-glance, and undetermined phosphates, and, what is more, interesting, double salts of copper and zinc.

A Boring male at Iford Manor, 1½ miles S.E. of Lewes, Sussex, yieled the following section:

The lower sand contained numerous grains of glauconite, while the upper bed was black when wet and consisted almost entirely of dark-green glauconite, with a few shell fragments and large quartz grains. The glauconite grains were small and were separated in an almost pure state by sieving; the portion coarser than 76 [wires to the inch] mesh contained the shell fragments, &c., while that below was nearly all glauconite, with a few very small grains of magnetite present in the sand.

The dyakis-dodecahedron (641) was observed on certain of the Museum specimens by Mr. Richard Elliot Steel in 1879 and again by myself in 1894; and although several memoirs on the crystallography of pyrites have been published since those dates, this form has not hitherto been recorded for the mineral.

Under the register-number 31679 are a number of small specimens and isolated crystals of pyrites, on three of which the form in question is deve]opod. These were purchased in 1860, and their locality is unknown. They show some matrix of black shale, and, unfortunately, are gradually being broken up by decomposition.

Among the specimens that were presented to the British Museum by Dr. C. T. Trechmann in 1917 from the collection of his father, the late C. O. Treehmann, was a loose crystal~ which at first sight appeared to belong to one of the lead-grey species so long associated with the Binn Valley, but measurements made on the three-circle goniometer in the British Museum did not accord with the angles recorded for any of the species hitherto described. The crystal was recently submitted to a careful examination, but still the bi-angular co-ordinates of the faces differ from those given for any other species, and the only conclusion that can be drawn is that the crystal represents a new mineral species, and one peculiar to the Binn Valley.

The following study was carried out in the Mineralogical Laboratory of the University of Cambridge upon specimens which were brought by myself from Japan. My hearty thanks are offered to Professor W. J. Lewis and Dr. A. Hutchinson for their kind permission to use the laboratory and the instruments, and for their constant help throughout my work.

Johannsen has recently described an areal method of micrometric analysis, based on the use of a planimeter in conjunction with a drawing apparatus. It is claimed that this method results in some increase of accuracy, a considerable saving in time, and—most important of all—eliminates all the eye-strain due to continuous reading of a micrometer.

It has been proved by the work ot Messrs. A. Hutchinson and A. M. Macgregor, recently published in this Magazine (1921, vol. 19, pp. 225-232) under the title 'Oil cornetite from Bwana Mkubwa, Northern Rhodesia', that the only difference—if any—between the Rhodesian mineral and the original cornetite from Katanga consists in the presence of cobalt as determined by Professor G. Cesàro in the crystals from the Étoile du Congo mine. It may be of interest to give here the results of my researches on the chemical composition of the cornetite from the Étoile du Congo mine in Katanga.

Graphic methods are often of the greatest assistance in bringing out the affinities of closely related minerals and particularly of members of isomorphous series. An illustration of the use of such a method in the case of a series involving three variables, all of them mutually replaceab]e, has already been given by the author in dealing with minerals of the tapiolite-mossite-rutile series. Recently, in studying a mineral of the spinel group, occurring in serpentine country near Namban, in the South-Western Division of Western Australia, it was found convenient to use a graphic method to bring out its relationship to the type minerals spinel, hercynite, and chromite, and to the intermediate minerals previously described under the names of picotite, chrompicotite, magnesiochromite, and magnochromite.

The only book on precious stones in which fibrolite is taken into account appears to be that of .J. Escard, ‘Les pierres précieuses’ (Paris, 1914, p. 190). He mentions the prehistoric stone implements made of dense fibrolite tbund in France, ~nd also states that the mineral is sometimes used as an ornameutal stone. Examples of such material are represented in ttm British :Museum collection of minerals by: a hatchet, measuring 11×½ cm., of pale yellowish-grey, compact fibrolite from N.W. France ; and a polished knife-handle, 9 cm. long, of greyish-white, transluceut, fibrous material with silky lustre. Clear material of good colour and cut in the form of a faceted gem has not hitherto been described.

During 1907, a plumbiferous barytcs, deposited by a hot spring at Hokuto in Taiwan (Formosa), was discovered by Mr. Y. Okamoto. This mineral, although a special name ‘hokutolite’ was proposed for it by Professor K. Jimbō in 1912, is a variety of barytes. It shows a slight difference in its chemical composition as well gs its physical properties from ordinary barytes.

The district round Lustleigh, near Bovey Tracey, is mined on a small scale for a very fine quality of micaceous haematite, which occurs there in well-defined lodes traversing the granite. This soft and powdery variety of haematite, known both locally and in the trade as ‘shining ore’, is used for a variety of purposes, but principally as the basis of a rust-proof paint. The ore and its mode of occurrence have been briefly described by J. S. Martin, and for the purpose of this short paper no fm4her description of the mines in general will be necessary.

In a general account of the properties of torbernite given by the present author in this magazine in 1916 it was shown that the transition from torbernite to the first dehydrationproduct, known as meta-torbernite I (meta-kupferuranit), was dependent on the temperature and the vapour-pressure, and that the boundary, of the stability area lay only a little outside the range of ordinary atmospheric conditions; the transition-point of torbernite in contact With water was determined as 75° C.

There are certain foreign minerals upon which the South African diamond has crystallized readily. The chief of these are garnet, ilmeuite, olivine, and iron-pyrites. In addition, zircon and mica are also probable inclusions. Cognate inclusions are graphite, bert of every kind, and diamond itself of unconformable orientation.

It must be our aim to correlate the external appearance of a crystal, and its physical properties also, with the arrangement of the atoms inside and the forces that join the atoms together. We might hope to gain so much knowledge on these points that, given a certain set of atoms, it would become possible to anticipate the design of their arrangement and to describe all the characteristics of the crystalline substance as consequences. The analysis of crystals by means of X-rays has given us a little help along this road, and we begin to see certain principles in broad outline.