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.

A meteoric stone found in 1931 by Mr. Bertram Thomas at Buwah (lat. 20° 3ʹ 10ʺ N., long. 51° 25ʹ E.) in the region of Suwahib in the Rub' al Khali, Arabia, has already been described in this Magazine. In 1932, Mr. H. St. J. B. Philby, travelling on a route some miles to the west of that followed by Mr. Bertram Thomas, picked up meteoric stones at three other places. Two of these are between 25 and 30 miles to the west of Buwah, and the third, Umm Tina, 3 miles north of Shanna, lies about 70 miles to the south.

Optical and microprobe investigations have been made on the metal and silicate portions of four particles > 1 mm extracted from the magnetic fraction of lunar soil bulk sanaple 14162,80. Three of the particles have structures and compositions similar to those encountered in the < 1-mm fraction of this bulk sample. One of the particles shows a complex arrangement of melted metal, unmelted metal, micronorite, and vitroclastic silicate material. The structure of this particle is reported in detail and its structure is explained in terms of preferential melting of metal-phosphide interfaces under the influence of shock events operating on material at a temperature of about 650°C.

This instrument, which was designed for use in the Crystallographic Laboratory of the City and Guilds of London Institute (Central Institution), is in its simplest form (Plate III.) a strong and inexpensive Wollaston Goniometer. It is, however, constructed in such a way that it may be converted into an instrument of greater precision (Plates IV. V.) by the simple addition of accessory parts to tho apparatus of Plate III. without any previous alteration.

L is the graduated disc, and B the milled head by which it is turned; the vernier v is not the slender tongue of metal which is usual in such instruments, but is engraved upon a portion of the fixed disc V; and L is kept in continual contact with V by means of a circular steel spring inserted between B and the bearing of the axle.

In examining a specimen of the rhyolitic lava-flow of the Rocehe Rosse, Lipari, in the collection of the Royal College of Science, London, I was struck by tile fact that the areas of pure black glass visible upon the fractured surface were each bordered by a band of spherulitic matter, the convex surfaces of the spherulites being directed inwards towards tile glassy area. The specimen, collected by Prof. J. W. Judd, F.R.S., evidently comes from a portion of the flow which has become breceiated during movement of the viscid mass; intermingling of glassy and hemicrystalline matter has occurred, and an approach to the structure of the well-known "Piperno" of Naples has resulted. But the irregular little lumps of obsidian have not received their spherulitic crust from any chilling effect that they may have had upon the surrounding groundmass; the spherulites belong to the glass-fragments themselves, and are not deposited upon their surfaces.

During the investigation of a zeolite it became necessary to separate small quantities of zeolitic material from a mixture of calcite and other heavier minerals; this could be done most easily by using a liquid of such density that the zeolite just floated, while all the other minerals sank to the bottom. A solution of potassium-mercuric iodide could not be used, as this reacts chemically with zeolites and alters their composition ; acetylene tetrabromide diluted with benzene was therefore chosen, and in consequence the apparatus had to be made entirely of glass. Certain dittlculties were found in using the ordinary form of glass separating apparatus, and to overcome these the form here described was devised.

Historical Introduction.—As given in modern text-books, the holohedral-cubic silver haloids occurring as minerals include the following species: the pure chloride, chlorargyrite, AgCl. ; the pure bromide, bromargyrite, AgBr; the intermediate embolite, Ag(Cl,Br), containing chlorine and bromine in varying proportions ; and iodobromite, containing all three halogens in a definite ratio corresponding to the formula 2AgCl.2AgBr.AgI.

The terms hornsilver (used by Gesner as far back as 1565) and cerargyrite (Beudant, 1832) are usually taken as referring only to the pure chloride. As regards their signification, however, they are equally applicable to all of the above species, and in lack of chemical analyses were certainly so applied in the past. Thus Breithaupt, after the discovery of the bromide and chloro-bromide of silver by Berthier in 1841 and 1842, remarks that many of the specimens of ‘Hornerz’ in the Werner Museum having a greenish colour probably contained bromine.

During a recent visit to Cornwall the attention of Professor Lewis was directed by Mr. James Wickctt to some composite crystals of copper pyrites recently found in one of the deep mines in the neighbourhood of Redruth. On the specimens acquired by the Cambridge Museum about thirty crystals show this composite growth, which causes the crystals to resemble ill-developed pentagonal dodecahedra of iron pyrites.

This Lamp is shewn half size in figs. 1 to 4. Fig. 1 is a section of the whole lamp ; fig. 2 a view from above ; fig. 3 shews the mode of folding the wick ; and fig. 4 the tinplate cover, which serves as a stand while the lamp is in use.

It is provided with a “bayonet” slot, which works over the little pin shewn in fig. 1, so as to keep the cover in place when it is put on over the lamp.

The body of the lamp is made from a piece of iron or lead gas pipe, 1 1/2in. internal diameter, to one side of which the wick holder is soldered. I find that “night light” grease suits admirably—ordinary composite candies do very well.

Several years ago Dr. Thomas Aitken, of Inverness, put into my hands a mineral which he thought to be new, with the request that I would analyse it.

He stated that the mineral occurred in veins in the conglomerate of the Old Red Sandstone, near Loch Bhruithaich, in Inverness-shire ; that it had been found by and given to him by the head gamekeeper on the Lovat property, and that similar pieces had been given to Mr. Wallace.

The specimens which he put in my hands, and others which he showed me, consisted of one side of a vein-plug, and were formed of alternate bands of foliated flesh-coloured baryte, with narrower ones of the substance in question.

In mineralogical literature there appears to be a tendency to overestimate the degree of exactness attainable in the chemical analysis of minerals. When it is considered how impossible in the majority of eases it is to obtain absolutely pure material for analysis, and how imperfect even in these days are some of the methods of chemical separation employed, for the determination of a formula any great reliance in the figures to the right of the decimal point in the percentages obtained is scarcely justified in the case of analyses made on small amounts (less than half a gram) of material.

As has been mentioned in the preceding communication, a supersaturated solution, which is cooling or evaporating, passes successively into the metastable condition, in which an introduced crystal can grow in it, and then into the labile condition, in which it may crystallize spontaneously. The transition is indicated by a sudden change in the refractive index of the solution. It seems possible that in these two distinct states of the solution there may be a difference in the mode of growth of the crystals. In the following experiments an attempt was made to find evidence of such a difference by the examination of thin drops of solution crystallizing under the microscope: and potash-alum was found to be a convenient substance for the purpose.

Sphærostilbite was one of a number of sub-species which Beudant in his Mineralogy, published in 1832, separated from ordinary stilblte owing to slight differences in chemical composition. In a typical specimen from the Faroe Islands he describes the sphmrosfilbite as innplanted upon ordinary stilhite, in the form of small globules, presenting a fibrous radiated structure and brilliant pearly lustre on the fractured surface. Unlike stilhite, it gelatinlsed with acids, and it also had a specific gravity (2.31) slightly higher than that of stilhite. According to the analyses given by Beudant, however, it differed in chemical composition so little from ordinary stilbite that in later text-books (Glocker, 1839; Breithaupt, 1847, &c.) it has always been referred to that species.

Mynydd Mawr is a conspicuous hill with a craggy face towards the north, and a well-marked corrie (Cwm Du) on that side. It lies to the south-east of Moel Tryfan and the west of Llyn Cwellyn (Carnarvonshire). On the Geological Survey map it is represented as a somewhat rounded oblong patch of felstone, about 1⅜ mile from east to west, and a mile, or a little more, from north to south, intrusive in Lower Silurian (Ordovieian) rocks, which are probably Arenig. I passed some years since to the north of the above-named face, and collected specimens from erratics which were plentifully strewn over the lower land. On microscopic examination I found them to contain a very puzzling and remarkable mineral which I have long intended to describe, but kept deferring this in hope of being able to revisit the place to obtain more specimens for examination, and by taking these from rock in situ, to prevent any question arising as to the true source of the rock.

It is now ten years since Sauer first described under the name of riebeckite a new species of blue hornblende in the granite of Socotra.

Since that time its occurrence in the British Isles has been noted in the " felsite " of Mynydd Mawr, N. Wales ; in the " microgranite " of Ailsa Craig, Firth of Clyde; in glacial deposits from the Isle of Man; Moel Tryfaen, N. Wales; Greystones, Co. Wicklow; and Greenore, Carlingford; in granophyre from Meall Dearg, Skye; and in felsite from Middle Eildon, Roxburghshire.

In the following list of 36 lives, with a range in ages frdm 56 to 89, the average age is 71.0 years. The average of 460 lives noticed in this Magazine since 1877 is 65.9 years ; and in the six numbers of this series since 1919 there has been a gradual and steady increase from 63.6 to 71.0.

Particulars respecting Czech, Italian, Japanese, and Russian subjects have been kindly supplied by Professors F. Slavlk, G. R. Levi, R. Ōhashi, and Mr. S. I. Tomkeieff respectively, and to these colleagues I express my thanks.