It is just over a hundred years since Charles Darwin, during his great voyage, visited Sydney, New South Wales. While there, he was given, by the explorer Major Sir Thomas Mitchell, a small and curiously shaped glassy object. In his ‘Geological Observations’ (1844) Darwin figured this object and speculated as to its origin, which he suggested was volcanic. This is the first recorded reference to what are now known as australites, many tens of thousands of which have been collected from widespread localities over the whole of southern Australia.

Investigation of serpentine minerals from metaserpentinized ultramafic rocks in two Archaean green-stone belts, east of Kalgoorlie, has indicated that antigorite, exhibiting a very wide range of textures in thin section, is the dominant serpentine species; however, it is locally accompanied by relict lizardite. Chrysotile occurs both in late tectonic veins and as a present-day weathering product of relict olivine. Analytical data and structural formulae on seven serpentines, characterized independently by X-ray diffraction analysis, support the chemical differences between antigorite and chrysotile postulated by earlier workers.

Up to the present time only one of the several ehildrenite occurrences known has been examined both chemically and crystallographieally. This is the well-known occurrence at the George and Charlotte mine near Tavistock, from which nearly all the specimens seen in collections were obtained. The crystals often attain a dimension of 1 cm., so that material for analysis can be easily obtained free from gangue. Crystals from this locality were analysed by Rammelsberg, Church, and Penfield, and it is on the results obtained by the last-named that the comparatively simple formula for this mineral is based.

Consider the poles of the faces of a crystal and the zones (great circles) which join them. Suppose we have given their gnomonic projection on to a certain tangent-plane to the fundamental sphere on which these poles and zones lie. We can find the gnomonic projection on any other plane by aid of the gnomonic net, as explained in this Magazine (1904, vol. xiv, p. 19); and similarly for the stereographic or orthographic projection.

The dehydration of thomsonite has recently been studied by Mr. M. H. Hey. The work here described was carried out in the Mineralogy Department at Oxford in the years 1925 and 1926. At the suggestion of Mr. Hey the results, though inconclusive by themselves, are now published for comparison with his own, which were mostly obtained by a different method.

It often happens in mineralogical inquiries that from scarcity of materials, lack of time, or other causes, the important datum of specific gravity is not secured. Now, however, that Sonstadt has shown us how to prepare a nearly colourless and perfectly transparent liquid with a density three times as great as that of water, there will generally be no difficulty in ascertaining the specific gravity of very many rare minerals as to which our knowledge remains imperfect. More than this, two minerals if of different specific gravities (provided one is less than S.G. 3.0), may often be easily separated from one another if they are in fragments of appreciable size. Thus, pieces of quartz with a S.G. of 2.655 float, while fragments of beryl (S.G. 2.691) sink in a solution having S.G.=2.67. A very simple apparatus is required for the purpose. (See fig. 7, Plate. VIII.)

The discovery of the meteoric stone near Lake Brown, County Avon, South-West Division, Western Australia, was recorded by Dr. Edward S. Simpson in the Annual Progress Report of the Geological Survey of Western Australia for 1921 (1922, p. 53). The following details concerning the meteorite are taken from that report and from a letter of September 25, 1925, sent by Dr. Simpson with the specimen, weighing 174 grams, which was presented to the British Museum collection by Mr. A. Gibb Maitland, at that time Government Geologist of Western Australia.

There are two distinct kinds of image which are the subject of optical investigation: object-images, in which the form of the object is reproduced, and directions-images, in which every point represents a direction followed by light before reaching the objective. An instrument that shows a directions-image may be described as a hodoscope. It is focused not on the object but on infinity, so that parallel rays are collected at the same point in the image.

The following brief notes on the occurrence of these gems in one of the least known portions of the Siamese ruby fields may prove of interest, as the particular district to which they refer has very rarely, if ever, been visited before by any European, whilst nothing at all has ever been written on the subject as far as I am aware. The notes are chiefly extracts from my journal for the months of May and June 1892, which I venture to present with as little modification as possible, in the belief that a description written on the spot is likely to give a more correct and vivid, even although it be a less highly finished picture of the locality than can be attained by any subsequent elaboration.

Gold and silver have been detected not only in the peculiar facies of the granite occurring on Bittleford Down, but also in the normal grey biotite-granite of numerous tor- and quarry-localities; several hand-specimens of granite showing minute flakes of visible gold have been collected.

The modes of occurrence of gold on Dartmoor, the environment of the granite from which specimens showing visible gold have been taken, and the gold-silver content of the granite generally have been investigated in some detail, with the results described below.

Numerous veins and veinlets of epidosite traverse the crystalline schists and associated igneous rocks of the Malvern complex. They art fine-grained, compact rocks, of uniform texture and pale greenish-yellow colour, and vary in composition from almost pure epidote to mixtures of epidote with small quantities of quartz, sphene, sericitic mica, apatite, and, in almost insignificant amount, albite.

Analytical investigation of these rocks revealed the fact that the epidote they contain holds its water more tenaciously than has hitherto been suspected : the determination of water-content by the methods usually applied to the analysis of rocks and minerals gave results which were so seriously low as to suggest that the mineral was essentially anhydrous. Though more drastic methods increased the yield considerably, they failed to liberate more than about 75 % of the amount of water which, theoretically, should be present.

An orange-coloured ochreous substance from Parys Mount, Anglesey, was recently submitted to analysis.

The observed loss of water at 100°C corresponds to 4H2O, which requires 13.24 percent.

In ordinary circumstances crystal-angles are measured by means of light reflected from the crystal-faces. In the partial or complete absence of faces the determination of axial ratios and angles may be impossible. In a recent investigation of certain derivatives of glyoxaline, an example of this was found. It was, in fact, the substance glyoxaline itself, which always occurred as long prisms having four faces in the prism-zone; the ends of the prisms were jagged and rough, and no siglls of optically reflecting-planes could be found on these ends. In such a case, X-ray methods of investigation are now available, and the problem in question is the determination of the dimensions of the unit-cell, not the complete X-ray inveatigation of the structure.

The accompanying engraving represents an exceptionally fine group of crystals ofapatite, found in the Untersulzbachthal in Salzburg. The dimensions are those of the original, its colour is white with a delicate tint of mauve. This group is the finest of three of the most magnificent specimens yet found at this or any other locality, the largest one having been deposited in the national collection of minerals at South Kensington, while the third was unfortunately broken.