During the last few years I have applied myself to the study of some minerals occurring in the sedimentary rocks of a definite geological horizon. The success of my investigations was greatly favoured by the fact that the mineralogical material was collected during the course of the systematic geological exploration of the phosphate deposits of Russia, which during the past eight years has been under my immediate supervision.

The explorations just mentioned were begun in the north-eastern part of European Russia, and several occurrences of barite were found in the first year during the field study of the phosphate deposits in the government of Kostroma.

In the Rose-Tschermak-Brezina classification of meteorites the intermediate class of stony-irons, in which iron and stony matter occur in approximately equal amounts and to which Maskelyne gave the name siderolites, is divided into (1) siderolites proper, including the groups of the pallasites and the siderophyres, and (2) lithosiderites, comprising the groups of tile mesosiderites, glahamites, and ]odranites. Mesosiderites are defined as consisting of iron and crystalline olivine and bronzite, and grahamites of the same constituents with the addition of plagioclasefelspar.

In the classification proposed by the author in a previous paper meteorites are divided into five groups according to the ratio of iron to nickel in the nickeliferous iron they contain. In the case of the meteoric irons such a classification, as shown by Farrington's list of analyses, is a natural one, since the structure of the irons, as revealed by etching, varies with the amount of nickel they contain. Thus Group 1, in which the metal is poor ill nickel, with a ratio of Fe to Ni of 13 upwards, includes nickel-poor ataxites, hexahedrites, and Coarsest and coarse octahedrites ; Group 2, in which Fe : Ni =8-13, the rest of the octahedrites from medium to finest ; Group 8, in which Fe : Ni = 5-8, nickel-rich ataxites; Group 4, in which Fe: Ni = 2-5, ataxites still richer in nickel; while Group 5 may include the doubtful Oktibbeha meteorite in which the ratio of iron to nickel is even less than one.

To mineralogists probably few spots in the world surpass in interest the little quarry hollowed out of the dolomite, just where the latter is cut by the Lengenbaeh, and about half a kilometre above the point where this stream ends its hurried course by joining the Binna at Imfeld, a hamlet lying in the main valley three kilometres above the village of Binn.

Considered from the crystallographical point of view the outstanding feature of the gnomonic projection is the fact that all great circles on the sphere, and consequently all zones on the crystal, appear on the diagram as straight lines. In order to secure its full advantages, it is necessary to take the plane of the paper at right angles to the axis of a zone, and preferably one of the principal zones of symmetry on the crystal.

The investigation of the Launton, Warbreccan, and Cronstad meteorites was undertaken with the object of placing on record descriptions of these stones. Launton and Warbreccan were found to conform very well with the type of Baroti and Wittekrantz, containing from 7-9 per cent. of nickel-iron, described in a previous paper. Cronstad, however, which contained as much as 18 per cent. of nickel-iron, showed so much variation from that type as to suggest a passage towards the rare Hvittis class of chrondritic stone containing even larger amounts of nickel-iron.

The Amana meteorite, known also as Iowa County, Homestead, and West Liberty, is fully described in O. C. Farrington's 'Catalogue of the Meteorites of North America'. After the appearance of a brilliant meteor which on the night of February 12, 1875, passed with loud detonations from S.W. to N.E. over northern Missouri and southern Iowa, about 100 meteoric stones, weighing altogether some 500 lb., were found scattered over an elliptic area of about eighteen square miles from Amana in Amahs township to Boltonville in Iowa township, both in Iowa Co., Iowa.

In Professor G. Cesàro's note 'Sur une propriété numérique de l'ensemble des axes de symétrie situés dans los plans de symétrie d'un polyèdre' is given the formula ((1) on p. 174)

Early in the year 1918 Mr. Atehur Russell picked up at the old antimony-lead mine at Glendilming in Eskdale, Dumfriesshire, Ipecimens of the antimony-lead ore Jound there, in which were small cavities lined with a drusy layer of mimlte crystals; these, being markedly deeper in eolour than the stibnite forming part of some of the specimens, belonged to a different species, and probably a sulphantimonite of lead. Mr. Russell blought some of the specimens to the Museum, and some of the small crystals were examined with the view of determining the species to which they belong.

In a paper published many years ago the following passage occurs under the section treating of seligmannite :—'Mingled with the se]igmannite, and partially coating the baumhauerite, are a number of very fine needles of a lead-grey colour, the nature of which I have as yet been unable to determine.' These needles form the subject of the present paper.

This species, a hydrous zinc phosphate, Zn3P2O8.4H2O, dimorphous with hopeite, was first described by Spencer in 1907. While the material then available was suitable for the physical and chemical description of the new mineral, it did not permit a full crystallographic investigation. Spencer noted that the crystals resembled in a general way those of hemimorphite, and made sufficient measurements to indicate the triclinic character of the mineral. In his sketch of a crystal he indicates that the mineral is twinned, and that this twinning is best seen on the perfect cleavage which is parallel to the brachypinacoid.

The widespread basaltic rocks of tile Brito-krctic province, like those of the Deccan and Columbia basalt plateaux, do not seem to have received from petrologists the attention they deserve. Descriptions of particular localities and their rocks are not lacking, and the British region in particular has become classic through the investigations of Judd, Sir A. Geikie, and Dr. Harker, but hitherto no attempt has been made to survey the province as a whole, except in the most general way.

The following is a simple general proof that, on the hypothesis that crystals have a homogeneous cellular structure, the only possible axes of symmetry are those with cyclic numbers 2, 3, 4, or 6.

According to this hypothesis, every crystal is entirely made up of minute space-partitions or ceils, which (apart from those of purely surface layers) have all the same form, size, internal configuration, orientation, and external relations. Accordingly, every point in one cell has an equivalent point exactly corresponding to it in every other cell.

In a previous paper attention was drawn to the close similarity in mineral and chemical composition of chondritic meteoric stones. In the case of about forty chondrites it was shown that, apart from variations in the amount of nickel-iron, not only are the constituent minerals present in very similar amounts, but their chemical compositions vary to no very great extent. In that paper sufficient importance was not attached to the variations in the amount of nickel-iron.