The specimen to which this paper refers, is one of a number of minerals from Kurdistan, presented to the Hunterian Museum, in Glasgow University, by Mr. D. Ferguson, to whom I am indebted for the following particulars of the occurrence. The exact locality is the Zarshuran River, in Kurdistan, where a large mineral vein, which has been worked for centuries for orpiment, is found. The country-rock is red sandstone, overlying, unconformably, altered slates and schists, which are intruded by a boss of felspathic granite or syenite. Near the surface the vein-stone is chiefly a kind of calc-sinter, but this disappears as the depth increases and calcite becomes the predominant mineral in the gangue, being associated with some quartz and fluorspar.

In nearly every thin section of a rock containing monoelinic pyroxenes it will be found that one or more crystals twinned on the orthopinacoid (100) are included. In such crystals the twin-plane is marked very clearly by the difference of relative retardation and extinction, and also by the interference-bands if the twin-plane is inclined to the plane of section. For the purposes of the complete optical determination, it is essential for the proposed method that one half of the twin should exhibit the emergence of an optic axis suitable for the determination of the optic axial angle by the Becke method.

Last winter I enjoyed the good fortune of spending some three months at Zweisimmen in the Bernese Oberland of Switzerland, in order to participate in the winter sports. Happily it proved a fine, cold winter of hard frosts and moderately heavy total snowfall. During such a stay in the crisp, dry cold of a snow-mantled world, the manifold and beautiful forms assumed by snow and ice are set before one in a manner impossible in this relatively warm and moist isle with its fleeting glimpses of true wintry weather.

Early in 1905 a small fragment of a meteoric iron from Uwet in Southern Nigeria was received at the Imperial Institute from Mr. John Parldnson, the Principal of the Mineral Survey then proceeding in Southern Nigeria. The fragment was part of a large mass which was held in great veneration by the natives of Uwet (lat. 5° 17' p N., long. 8° 15' p E.), a town on the Calabar river, about 23 miles north by west of Calabar. Later, further particulars of the meteorite were communicated to the Imperial Institute by Mr. E. D. Simpson.

Some specimens of calcite which I obtained recently from a chalkpit at Corfe Castle in Dorsetshire appear worthy of description on account of their somewhat unusual habit and of the rarity of wellcrystallized minerals in the Chalk.

The pit is situated in the Upper Chalk, not far from the great overthrust fault which traverses the Isle of Purbeck from west to east along the boundary of the Chalk and the overlying Tertiary beds. The Chalk is here steeply inclined, with a northerly dip, and is much indurated, being sufficiently hard to be worked for road-metal.

The mineral hero described was recently collected by the officers of the Geological Survey during their work for the six-inch map of the Island of Mull. It is present as minute phenocrysts in a dark, glassy, magnetite-bearing rock/which is intruded as sheets in the Tertiary lavas nearly one mile south-south-west of Pennygael.

The small rounded crystals of augite are seldom more than ½ mm. in diameter and are traversed by irregular cracks. They contain a few negative crystals, and are occasionally darkened, probably with included magnetite. They appear to have been reabsorbed to some extent by the matrix.

The crystals to which this paper refers are found at Bail Hill, about three miles north of Sanquhar, in Dumfriesshire. At this locality volcanic rocks of Arenlg age outcrop in the midst of the greywacke of the Southern Uplands. The rocks are mainly lavas, and include some coarse-grained tufts which are composed chiefly of augite- and hornblendeandesites. Ill the andesitic fragments, there arc numerous porphyritic crystals of a black augite, which call be easily separated from the rest of the rock. Isolated crystals of augite and hornblende occur also in the matrix of the tufts. No mention of this occurrence is made in Heddle's 'Mineralogy of Scotland', and apparently the only reference to it in previous literature is the short petrographic description in the Geological Survey Memoir.

During the last decade there has been no lack of controversy on the subject of rock classification, but the dispute has concerned igneous rocks almost entirely. Petrography has been threatened by an effort to reduce it to an independent science of igneous rocks, and in consequence of this there has been a tendency to neglect its wider aspects. Important as igneous rocks are, their formation is less well understood than is that of some other sub-groups of rocks ; moreover, they constitute one only of some six or seven sub-groups, and it is the business of petrography as a science to deal with these rocks as a whole. The student of petrography should be encouraged to take this wider view. He shonld look at these different sub-groups of rocks in their proper geological perspective, and approach the study of the classification of igneous rocks with a knowledge of the principles that are applicable to the classification of rocks as a whole.

The discussion concerning the classification of ore deposits has proceeded on independent lines, and in a more well-balanced manner than has that of rocks. With ore deposits, as with rocks generally, genetic principles have triumphed; but the application of these principles to rocks long preceded their application to ore deposits. Iu recent years it has become apparent that the fundamental requirements for the classification of rocks and ore deposits are essentially the same ; and in view of the identity of their interests, both subjects are treated in this paper.

The aims of this paper are : To define the basis of genetic classification ; to give a brief historical account of classification on genetic-geological principles ; to point out defects in the present system of arrangement ; and to suggest an altemmtive scheme of grouping that is in closer accord with geological and genetic principles.

The mineral adamite (Zns(AsO4)2.Zn(OH)2), discovered by C. Friedel in 1866 on specimens from Chafiarcillo, Chile, has since been found at only two other localities, namely Cape Garonne in France and Laurion in Greece. At the original locality it would appear to be of rare occurrence, since in the literature mention is made of only two specimens.

It was therefore of interest to find in the British Museum collection a good specimen of adamite from Chafiarcillo. This was found amongst the hornsilvers, and the associated adamite had been thought to be fluorite, which indeed, at first glance, with its violet colour and good cleavage, it closely resembles in appearance. The crystals are remarkable by reason of their very strong pleochroism, and as this feature of adamite has previously received no mention it has been thought worthy of placing on record.

The apparatus to be described has been designed for the cutting of parallel plates and of prisms of crystallized substances in any required direction. The authors have endeavoured to design a small apparatus, simple in construction and easy to manipulate, which at the same time will be capable of yielding results of sufficient accuracy for most optical work on minerals. Several instruments have been devised with the same objects in view, notably those of E. A. Wülfing, G. Halle~ and F. Stöber. The well-known cutting and grinding goniometer of Dr. Tutton is an instrument of an entirely different class.

About the middle of 1911, I was commissioned to report on a copper mine known as the Umkondo, situated in the south-east of Mashonaland, the eastern province of the territory of Southern Rhodesia. The mine is in a very out-of-the-way spot, about 120 miles from Odzi station, the nearest point on the railway, and to reach it took five days of somewhat rough travelling by cart.

In 1904 Professor Bowman described the occurrence of bertrandite at the Cheesewring Quarry, Linkinhorne, Cornwall; the mineral having been then recently discovered there by Mr. F. H. Butler. The following notes contain an account of the character and mode of occurrence of the same mineral at four additional localities in Cornwall.

It is only recently that the mineral topaz has been found in any considerable quantity in Canada. Previous to the discovery of the topaz of York County, New Brunswick, in 1911, it was distinctly a rarity among Canadian minerals and had never been found crystallized in any Canadian locality. The above-mentioned district, however, has yielded both the massive and crystallized varieties in fair abundance and some fairly perfect crystals have been obtained for measurement.