In a receipt paper descriptions were given of some meteoritic masses, which had been brought from the Desert of Atacama and are now in the British Museum. Several of them were independent of those preserved in other Meteorite Collections, in that they showed no signs of having been broken since their discovery; but it still remained to determine whether they might not possibly belong to meteoritic showers, of which individual masses had been already collected and described.

For this a minute investigation of the meteoritic literature of the Desert of Atacama was necessary.

In the summer and autumn of last year I paid a visit to Iceland, and I as I had been told by my friend, Mr. Madan, that the difficulty of obtaining large pieces of clear calcspar for optical purposes had been exciting some curiosity as to the state of the quarry itself, and as the peculiarity of the deposit made it an object of interest, I thought it worth while to force Eskirjördhr into my route. The narrow fjords of Sudhrmúla Sysla, of which Reydhartjödhr, the largest, bisects the East coast of Iceland, are cut out of an immense plateau, formed of horizontal sheets of Volcanic rock—chiefly trachyte—between three and four thousand feet high. This has been subsequently eroded into sharp bare ridges with immense cliffs or steep slopes falling from them, parted by torrent valleys and fjords ; the greater part of the district not reaching the present snow-line.

This mineral was found upon several specimens of argentite from Chañarcillo which were acquired for the British Museum in 1886.

The specimens consist of argentite in large drusy octahedra implanted on quartz or calcite, and associated with proustite and a little asbestos.

The proustite is mostly in the form of small brilliant prisms with sealenohedral terminations {201̅}, capped by the rhombohedron {110}, which are grouped upon the argentite. But dispersed on the argentite, together with these crystals of proustite, are a number of fine glittering scales, which present at first sight precisely the appearance of the pyrrhosiderite or göthite of Siegen, having the same bronzy red colour, and a lustre resembling that of earthy haematite when seen on the matrix, that is to say partly by reflected and partly by transmitted light. Under the microscope the scales are easily distinguished from göthite ; they are without striations, remain dark when rotated between crossed nicols, and appear of a nearly blood-red colour by transmitted light ; whereas scales of göthito are striated in one direction, and exhibit marked differences of absorption when rotated above the polariser.

A stone called sang-i-yashm in Persian, which has some points of resemblance to jade and is sometimes mistaken for it, is utilised at Bhera, in the Shahpur District of the Punjab, for the manufacture of dagger hilts, knife handles, caskets, amulets, and other articles. It is also found useful in mosaic work.

I am indebted to Mr. J. Wilson, B.C.S., Deputy Commissioner of the Shahpur District, for several specimens of the stone in the unworked state, and for information regarding its place of origin. Other specimens I obtained from my son Lieut. A. H. McMahon, Assistant Commissioner, Kohat.

The sang-i-yashm is a hard species of serpentine which seems to correspond very closely to that named bowenite, after Dr. Bowen, who, in 1822, published an analysis of a mineral from Smithfield, R.I., which up to that date had been called nephrite.

None of the mineralogical problems of the present day are of greater importance than those which deal with the nature and causes of the modifications which crystallised bodies undergo as a consequence of changes in their environment. It is above all things necessary that we should clearly discriminate in every case between the characters of minerals which are original and essential, and those which are accidental and secondary, and which result from the action of various mechanical and chemical forces upon crystals, subsequently to their formation. No fact is more certain than that crystallized minerals, without losing their identity, may have their chemical composition altered within certain (often very wide) limits; and that, as the result of chemical action or mechanical strains, profound changes may take place in all their optical and other physical properties.