In a recent number of this Magazine (1897, XI. p. 192) a paper by me on "The Crystallography of Plagionite" gives the results of goniometric measurements and specific gravity determinations made on crystals of plagionite from Wolfsberg in the Harz; it was also suggested on crystallographic grounds that the mineral from Arnsberg in Westphalia described by Pisani as heteromorphite was identical with plagionite: but as no quantitative chemical analyses were made on the material measured, these results were not altogether satisfactory.

The rock-specimens collected during the Antarctic Expedition of 1839-43 were deposited in the British Museum. A few years ago, in the course of a re-arrangement and registration of the rock-specimens n the Museum, this collection amongst others was examined, and microscopic sections of some of the specimens were prepared. Nothing, however, was published at that time, since it was found that the greater part of the collection had been practically duplicated by the rocks of the Challenger Expedition, which had a year or two previously been deposited in the Museum, and it was felt that mere petrographical descriptions of specimens have but little to recommend them in the absence of geological data as to the mode of occurrence and mutual relations of the rocks in the field.

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.

The specimens described in this note were collected by Mr. Sydney Ryan, Managing Director of the Ryan Tin Mines, and were presented by him to the British Museum through Mr. John Ballot, who brought them to England.

They were found in the stanniferous gravels of the Embabaan district in Swaziland, S. Africa. Their probable source is the granite-gneiss which forms the base of the rock-series in that district.

In this paper are embodied the results of an examination of the specimens of lead slags from Laurium in the British Museum. On some of the specimens a new mineral, paralaurionite, was found, which possesses the same chemical composition as laurionite, but entirely different morphological and optical characters.

In addition to crystals of the four minerals given in the title, a few crystals oi matloekite and anglesite were noticed, and on one specimen there is a radiating group of prismatic crystals of penfieldite.

A Specimen in the University Museum consists of black tetrahedral blende, exhibiting perfect metallic lustre; indeed, the brilliant steely cleavage surfaces of the mineral and its metallic tarnish raised a doubt whether it could really be blende; but in very thin fragments viewed by transmitted light it is seen to be brown in colour.

This mineral was originally described as a hydrated copper-arsenate. Analyses of copper-arsenate are given as far back as 1801 by Vauquelin (Journ. des Mines, 1801, X. 562), and by Chenevix in the Philosophical Transactions (for 1801); but at this early date the analyses seem to refer partly to ehalcophyllite and partly to olivenite.