So far as I am aware no account of the microscopic structure of this rare and beautiful rock has yet been published. I have, therefore, thought that a brief description of its structure and some considerations concerning the origin of tourmaline rocks may be of interest to petrologists.

Boulders of the rock, as is well known, are abundant in the vicinity of the village of Luxullian (about five miles from the town of St. Austell, Cornwall), where I collected specimens in tho autumn of 1873; but I believe the rock itself has never been discovered in situ, though veins of different varieties of tourmaline rock are abundant in the granite of this and other districts in Cornwall, some of which occasionally rather resemble it, and the mineral frequently occurs in the granite itself, the felsite cleans, and the altered sedimentary rocks.

Professor Heddle remarked, that this title would sound strangely, to southern ears; as in England and probably also in Ireland, the putting money enough in the pocket, and proceeding to the shop of a dealer, was the ordinary, and indeed the all sufficient method; though some enthusiastic collectors might go so far as to visit the openings of mines; while some adventurous ones might even explore them. In Scotland no such method of procedure could be adopted; there were absolutely no mineral dealers now in Scotland; there were almost no mines, and of these none now yielded minerals of special interest.

The Geological Survey Map of CornwalI shews, to the south of the town of St. Austell, several patches of “greenstone,” extending from near the ancient earthwork called Trethullan Castle, on the west, to the sea at St. Austell Bay in the east ; a distance of over four miles.

The western end of the most extensive of these patches swells ont on the top of the hill to the north-east of St. Mewan Church, so as to cover several hundred acres (including some of the best land in the parish). This was described by Mr. J. Arthur Phillips some years since in the Philosophical Magazine. Mr. Phillips speaks of the rock as being distinctly crystalline, consisting of felspar (sometimes triclinic) ; semi-transparent yellowish-brown crystals, probably hornblende ; a green fibrous mineral also believed to be a variety of hornblende ; many black grains of oxide of iron and a few hexagonal crystals, probably apatite ; and he says the rock exhibits unmistakeable evidence of extensive alteration. Speaking of its extension eastward, he says “it extends in diminished proportions in a southeasterly direction to the sea at Duporth.”

Scarcely in any case has the meteoric origin of any iron been more doubtful than that of the Greenland masses found by Professor Nordenskjòld in 1870, for although they contain about 2 per cent. of nickel, and, when etched, show the Widmanstätt’s figures, the fact that iron is imbedded in the basalt, on which the so-called meteorites were lying, bespeaks that the loose masses of iron originally belonged to the basalt.

“The Blue Rocks” (Danish, Blaafjeld, Greenland, Ovifak), on the southern coast of Disko, where the iron was found, are about 1800 feet high; the foot up to 600 or 700 feet is covered by loose stones forming a slant of 30 or 40° above which, in the almost perpendicular rock, 13 or 14 horizontal seams of trap are seen.

In commencing the proceedings of the second Annual Meeting of the Mineralogical Society of Great Britain and Ireland, allow me to express the pleasure which it gives me to be present here to-day, and my regret that I was not able to attend the first meeting last year at Glasgow. I feel it to be incumbent on me to give some opening address, but at the same time it must not be long, since many other subjects claim attention.

In the first place I think I may well congratulate the Society on its present condition, and contrast it with some of the predictions made little more than a year ago. We were told by men well-known in the mineralogical world that no such Society as our own could possibly be established—that, even if it could, it would be of no use, unless it published a Journal—which it most certainly never could afford.

I have when travelling, so often wished for some little indication of the scientific features of the country, beyond the meagre information of the guide book, that it occurs to me to suggest collaboration amongst mineralogists for mutual information.

With a view to this, could we not agree to take some localities and work out their details, spending our holidays in un-hackneyed districts, at quiet inns and in fresh air, each reporting his results succinctly in the Mineralogical Magazine, with a sketch map where wanted ?

As a little-worked-out place, I for my part nominate the Val d' Anniviers or Einfischthal, leading from the town of Sierre, in the valley of the Rhone, at nearly right angles to it, into the very heart of some of the suhlimest scenery of the Swiss Alps, and, as it will be seen, affording great facilities for meteorological, botanical, geological and mineralogical studies, economical quarters, warmhearted people, and excursions and scrambles of every grade of length and difficulty.

The author exhibited and described the small additions that need be made to an ordinary microscope, in order to make it available for the above-named purpose, and also gave a few illustrations of its application to particular minerals. So far, however, the instrument has been used only sufficiently to prove that the method gives excellent results. The author thinks it desirable to defer a complete decription of the construction and use of the instrument until he has been able to examine a sufficient number of minerals to publish a table of their indices of refraction for practical use. It may, however, be well to say that the addition to the microscope consists only in a small graduated scale attached to the body of the instrument, and vernier to read off to th of an inch. This enables us to measure the extent to which the focal length of the object glass is increased by looking through a more or less transparent miueral, and also its thickness in the part thus examined.

In making an examination of some samples of Phosphorite, recently discovered in Southern Russia, I was much struck by the unusual appearance of the substance, and after a closer examination came to the conclusion that it was a new form of the mineral, and ought to be brought before the notice of this society, in order that its occurrence and physical structure might be recorded and discussed.

The mineral which forms the subject of this paper occurs in rounded masses, varying in size from 5 to 9 inches in diameter. The outer surface is smooth and presents an appearance highly suggestive of the form being due to the action of running water, but upon fracturing several of these balls I found in every instance that they were c6mposed of a number of fibres radiating from the centre, of small size, and of a blueish grey colour, having a hardness of about 4.

Quite recently I obtained from an importation of Japauesa curiosities two pairs of chop-sticks which were catalogued and sold as jade. Under this name arc often included, not only the true jade or nephrite, with a hardness of 6 and a specific gravity approaching 8, but also three other mineral species. Of these jadente is not only harder but heavier than jade : prehnite differs but slightly from jade in either of these characters; while flour, the remaining species referred to, has a hardness of 4 only. Had the specimens to which I now direct attention belonged to any of the foregoing species, they would have been worthy of notice on account of their extraordinary size, or rather length, and also by reason of the beauty of their appearance. But after I had determined these objects to be serpentine, I thought some particulars as to their characteristics might prove of service in identifying one of the materials employed in oriental art.

In carefully reviewing the various facts which I have been able to collect since the publication of my paper on the microscopical Structure of Crystals, I have been led to believe that many peculiarities in the structure of granitic rocks may be explained by a principle, which, as far as I am aware, has not hitherto attracted attention. It appears to me extremely probable that the critical point in the consolidation of granitic rocks is very closely connected with the critical temperature at which highly heated and compressed steam would condense into an equal volume of highly heated and expanded liquid water.

As I pointed out in the paper already mentioned, rocks melted under great pressure probably contain water either dissolved as a gas in a liquid, or in the state of a fused hydrate. On cooling down to a lower temperature, the crystallizing out of anhydrous minerals would almost necessarily set free this previously combined water. As long as the temperature was above the critical point it would necessarily remain more or less disseminated in the rock as highly compressed steam, but as soon as the temperature fell below the critical point, it would condense into highly expanded liquid water.

Through the kindness of Prof. and Mr. John Young, F.G.S., I have been enabled to examine a number of unclassed minerals belonging to the Hunterian Collection in the Museum of the University of Glasgow. Among them I have found some whose composition differs from anything already described, and it is with the hope that mineralogists may be enabled to identify them elsewhere, that I now publish a detailed account of them. I am sorry that it is impossible for me to state the localities of some of the minerals, owing to the fact that they were unnumbered and unknown specimens, which were found in olcl drawers of the museum when the collection was being removed to the new buildings, but as the minerals with which they are associated are characteristic, we may obtain some clue to the deposits in which they originally lay. I shall describe the minerals in the order of their complexity, giving the least complex the first place.

In the year 1874 the steamship Faraday whilst engaged in grappling for the broken telegraph cable, caught the strong claws of the grapple in a rock, which resisted with the strain of about 27.5 tons, to which any but a rope of marvellously perfect manufacture would have yielded. As it was, the rock gave way, and a lump of black basalt came up weighing 21 lbs. This mass shewed signs of having been torn off. The fragment, and the section made from it for the microscope which accompanies this memorandum, were submitted to Mr. J. Clifton Ward, who has kindly examined the specimen, and drawn up the report enclosed herewith.

I cannot find in any charts indications of the habitual voyage of icebergs so far eastwards in the same latitude as the spot in question, and I have consulted Dr. John Rae as to the question of the rock being from an ice-borne mass. He says in reply, that he is not aware of icebergs having been seen about that spot, but that such an occurrence is not impossible. He thinks it more likely that, as I had suggested, the fragment was wrenched off some submarine peak or summit or ridge.

A few years ago, while inspecting some iron ore deposits at Smallacombe, near Bovey Tracey, in Devon, I noticed the occurrence of certain brightly colored green, red and brown clays in considerable quantity. I took several specimens of the green clay at the time, and on my return home laid them aside in a lumber closet, where they became buried with other specimens, from which they have only lately been disinterred. After so long a stay in a tolerably dry situation I thought they might be regarded as in a normally hygrometric condition, and it was in this state that I subjected then to examination and analysis, with the following results.