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.

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.

In August 1904 I discovered in the Lengeubach quarry a specimen on which were three small, round-shaped crystals, about the size of small shot, grown upon a prismatic crystal of sartorite. I measured them, and owing to their small size experienced some difficulty in determining the position of some of the faces with the goniometer at my disposal, which was of the ordinary single-circle pattern.

This form of goniometer was designed in order to provide for the use of students of elementary crystallography, at as moderate a cost as possible, an efficient instrument for the measurement of the interracial angles of crystals. It is of the customary type, in which the direction of reference is given by the reflection of a distant object in a small plane mirror without optical aid, and the axis of the grHduated circle is horizontal. The mirror measures about 45 by 25 ram. and its frame is rigidly attached to the ball of a ball and socket joint, so that it is adjustable in any direction; the socket is split, and a screw linking the halves enables it to grip the ball firmly.

The substance was met with in the course of work on steel-furnace slags, a general account of which has been communicated to the Iron and Steel Institute. These slags were for the most part melts consisting principally of the three oxides FeO, MnO, and SiO2, and yielded the silicates fayalite and rhodonite. The small amount of calcium silicate usually present is held in isomorphous solid solution ill these silicates, but when the amount of lime exceeds about eight per cent. a new silicate appears, which does not seem to belong to any of the known mineral groups.