Some time ago I was informed that galena was being obtained in a sandstone quarry at Aimville, about two-and-a-half miles north of Kirknewton, which had been recently re-opened for the purpose of supplying building material in connection with the extension of the Harperrig Reservoir, belonging to the Edinburgh Water Trust. As I saw no likelihood of my soon being able personally to visit the spot, I mentioned the fact to my friend, Mr. Alex. Lumsden, M.E., who I knew had sometimes occasion to pass near the locality, at the same time telling him that I did not attach much importance to the alleged occurrence, and that I did not expect that it would be of such interest as to be worthy of a special visit. Subsequent investigation showed, however, that I was mistaken, and as the mode of occurrence of the mineral is so unusual, some account of it may not be without interest.

Few, if any, analyses of British aragonites have been published; that which I now submit was executed upon a specimen forwarded to me by Professor Heddle, who has supplied me with the following notes of its occurrence.

It was obtained by him at Sobul Hill, in Unst, Shetland.

The west side of the hill of Sobul is pitted for the extent of nearly a mile with quarry holes, opened in a search for chromite.

As the preliminary examination of the Makariwa stone had already indicated to Professor Ulrich the presence of mineral constituents having the physical characters of olivine, enstatite, glass, a substance resembling glass, nickel-iron, troilite, magnetite, hydrous oxide of iron, and possibly chromite, the quantitative chemical anslysis presented obvious difficulties, among which may be specially mentioned the fact that one chemical element (iron) enters into the composition of each of the above fine-grained and closely intermingled constituents. This chemical examination I was invited to undertake by Professor J. W. Judd, F.R.S., through whom the two fragments of the stone sent to this country by Professor Ulrich have been generously presented to the British Museum.

Now that the measurement of extinction-angles in cleavage-flakes is frequently used to assist in the identification of minerals, the question of the relation of angles so measured to the orientation of the optic axes is one that must frequently arise. I confine myself here to the case of monoclinic minerals, such as hornblende and augxte, in which the optic axes are parallel to the clinopinacoid and the cleavage is prismatic.

In the present paper an attempt will be made to summarise known facts respecting the mode of occurrence of gold in its matrix, and to draw certain inferences from these facts as to the manner in which the gold has been deposited. The general opinion of miners that it has been introduced by igneous action, in a state of either fusion or volatilization, does not agree with modern theories of the origin of metalliferous veins, which ascribe their existence to hydrothermal action, or at any rate suppose the metals to have been introduced in aqueous solution.

The mineral which forms the subject of this communication came from the gem mines of Rakwana, Ceylon, and was brought to England by Mr. Joseph Baddeley, who, while superintending operations there, had formed a collection representative, it was believed, of almost every kind of pebble to be found at the works. This collection Mr. Baddeley, on his return home, submitted to Mr. Pringle at the Museum of Practical Geology, London. In looking, from time to time, over the collection, Mr. Pringle had occasion to take the specific gravity of some of the specimens. Amongst those so tested were certain pebbles the sp. g. of which was found to be about 3.98. This resuIt, combined with their other physical characters, having rendered it impossible for Mr. Pringle to assign them to spinel, ilmenite, or other species with which he could compare them, he handed the pebbles over to me for chemical analysis.

The crystalline form of orpiment was first determined by Mohs (Grundriss der Mineralogie (1824), 2, 613).

His measurements, which he is careful to state were only approximate, gave an angle of 79°20' for the prism, and 83°7' for the brachydome; the plane of perfect cleavage being taken as the macropinakoid, and the crystals being referred to the orthorhombic system.

Some specimens of this rare mineral have recently been kindly forwarded to me by Mr. J. R. McKay, Manager of the Broken Hill South Silver Mining Company, New South Wales, together with a report upon them by Mr. J. O. Armstrong of the above mine, and Mr. A. D. Carmichael of the Broken Hill Proprietary Block 10 mine, as follows :—

“Mineral found at the Broken Hill South Mine, at the 300 feet level in the carbonate of lead stopes, below original water level.

Shortly after the Meeting of June 16th, at which Mr. Dick gave the description of the characters of Geikielite, Mr. Joseph Baddeley, who had brought the specimens from Rakwana (or Rackwanné) (80°40' E., 6°25' N., in the District of Kollonnagam, Ceylon), courteously offered to present one of them to the British Museum for preservation in the Mineral Collection: the rest of his small store of eight or nine stones, picked out by him from a heap of other dense pebbles, he required for sending as samples to those friends in Ceylon whom he wished to interest in a search for further material.

I believe that the green ' Skin' of Agates will prove to be celadonite and not delessite, as has been generally supposed." This is an extract from a paper by one of us, which was published in 1879 in the Transactions of the Royal Society of Edinburgh.

Quarrying for agates upon a large scale having been carried out for several weeks during a succession of years on the shore of Forfarshire, an unusual supply of tile soft coating which frequently invests them was obtained.