Some time ago a specimen studded with small but well developed crystals of a sky-blue mineral, supposed to be percylite, was offered for the British Museum collection : the rarity of percylite and the excellence of the crystals on this specimen rendered a careful examination desirable. The specimen had been obtained from the Mina Beatriz, Sierra Gorda : on a large-scale chart, kindly placed at my service some years ago by Mr. George Hicks, of Newquay, Cornwall, Sierra Gorda is shown situate between the Bay of Mejillones and Caracoles, about 20 or 30 miles from the latter; longitude 69°29' W. of Greenwich, latitude 22°55' S. : at the truce of 1884 possession of this district was temporarily assigned to Chili.

Some experiments on the hydrophane recently found in Colorado led Mr. G. F. Kunz (Am. J. Sc. XXXIV. pp. 479-480, Dec. 1887) to the extraordinary conclusion that this mineral absorbed more than its own bulk of water. Mr. Kunz, with great kindness, furnished me with a supply of this variety of opal from the locality in question. I can confirm the accuracy of his experimental results, but not of his deductions therefrom.

The locality of the specimen which is the subject of the present note is Namaqualand, South Africa. It was brought over from Africa, together with other minerals, about the year 1861, by Mr. Edgar Layard, who was at that time acting as curator of the Museum at Cape Town. It was in the same year that Mr. Layard presented to the British Museum Collection specimens of Namaqualite, the mineral which was subsequently examined by Professor Church and shown to be a new species. The connellite was given by Mr. Layard, among other specimens, to Mr. T. Davies, who in 1887 presented it to the Museum. It was not recognised as certainly connellite, but was put aside for chemical examination as being either clinoclase or connellite.

Last Easter, when I was with Professor Hughes and his geological students at Torquay, I found some very perfectly preserved pseudomorphs of hæmatite after iron pyrites. They occur in the calcareous red shale in the most northerly part of Saltern Cove, Torquay, where the unconformity of the Trias and the Devonian is well shown.

Few mineralogical problems are of greater interest at the present time than those connected with the metamorphism of rocks. We are called upon to determine the exact series of processes by which a rock, having a particular texture and consisting of certain mineral species, is converted into a totally dissimilar rock, possessing, not only a different structure, but a distinct mineralogical constitution.

Some little time ago I observed very large and fine specimens of gyrolite among a number of zeolites which a friend had lately received as a gift, from the cuttings on the railway from Bombay to Poonah—the locality for the fine apophyllites. These occurred in specimens much larger than those in which the mineral is seen in Iceland, Faröe, or Scotland.

This substance was found by Mr. Dudgeon at the Pibble mine, which is directly opposite to Cairnsmore of Fleet, in Kirkeudbrightshire, and is within a few miles of Creetown.

This mine was worked for lead, and a few pieces of copper-nickel (nickeline) were obtained at it. The blue variety of the silicate of zinc also very sparingly occurred, and there were slight appearances of the phosphate and of the carbonate of lead.

This mineral Occurs in thin hexagonal plates with bevilled edges, which were formerly referred to the rhombohedral system, on account of their characteristic triangular striations, which run parallel to alternate edges of the hexagon.

Des Cloizeaux in 1867 (Nouvelles Recherches, p. 85) found the crystals from Freiberg, which are sometimes sufficiently thin to transmit light, to be biaxal, the acute bisectrix being perpendicular to the surface of the plates; the apparent angle between the axes could not be determined accurately, but was found to vary from 63° to 88°. The mineral must consequently be regarded as orthorhombic, with a prism angle very near to 60°.