During the last few years some fresh specimens of Sparable Tin have been raised from various mines in Cornwall; a description of this variety may therefore be of interest to the Society.

The value of this description of the now finds will perhaps be increased by combining with it an account of the specimens of Sparable Tin from different mines now to be found in our museums and private collections. Through the kindness of those gentlemen who own or have charge of these collections, I have been enabled to see and examine many of the interesting specimens which they contain.

The name "Sparable Tin" is peculiar to Cornwall, and has been given to this variety of Cassiterito on account of its so-called resemblance to the sparable nail of the cobbler.

The work of tile late Hermann Vogelsang, and the subsequent researches of O. Lehmann and other observers, have done much to show that a careful study of the rudimentary forms of crystallisation may prove as valuable to the mineralogist as that of embryology has already been to the comparative anatomist.

It is, indeed, difficult to form any clear conception of the manner in which a crystallite originated, nor can we go further back in the history of its development than a stage in which a number of atoms have been grouped in an arrangement about which there is yet no certainty, thus forming molecules grouped in some manner about which we are equally uncertain. We can but imagine that there is some inherent property in molecules which causes them, under given conditions, to group themselves in an orderly manner and to assume a form which may, when more fully developed, be referred to one of the recognlsed crystallographic systems.

Stephanite has been the subject of two important memoirs. Schröder examined minutely the crystals from Andreasbcrg ; Vrba has described fully the character of the stephanite from Przibram and other localities, and has given at the same time a summary of the observations of previous mineralogists, so that his memoir constitutes a monograph of the mineral.

By neither of these observers, however, nor elsewhere, has it been stated that stephanite is hemimorphic, although it has been suspected of being possibly hemihedral.

It is the object of the present paper to establish the hemimorphism of stephanite upon evidence similar to that which has been employed in the case of pyrargyrite.

Crystallised, substance from a blast-furnace at Mostyn, in N. Wales, having been brought under my notice by Mr. Heywood, of St. Mellons, it was thought worth while to subject it to a careful examination. The largest of the crystals was about 6 mm. long and 2 mm. in diameter. They were translucent, varying in eolour from almost colourless to honey-yellow, and were arranged in tufts on what seemed to be altered firebrick. They yielded a pale yellow powder of which the specific gravity was found to be 5·605.

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 examining a specimen of the rhyolitic lava-flow of the Rocehe Rosse, Lipari, in the collection of the Royal College of Science, London, I was struck by tile fact that the areas of pure black glass visible upon the fractured surface were each bordered by a band of spherulitic matter, the convex surfaces of the spherulites being directed inwards towards tile glassy area. The specimen, collected by Prof. J. W. Judd, F.R.S., evidently comes from a portion of the flow which has become breceiated during movement of the viscid mass; intermingling of glassy and hemicrystalline matter has occurred, and an approach to the structure of the well-known "Piperno" of Naples has resulted. But the irregular little lumps of obsidian have not received their spherulitic crust from any chilling effect that they may have had upon the surrounding groundmass; the spherulites belong to the glass-fragments themselves, and are not deposited upon their surfaces.

The subject of this note derives interest less from its novelty than from the beautiful manner in which the intergrowth is exemplified in Nature. As Sadebeek has shown, the intergrowth of marcasite and pyrites takes place according to two laws.

(1) The vertical axis of marcasite is parallel with a principal axis of pyrites; one of the two other principal axes of the latter being parallel with the combination edge m (110) ∞P : c (001) 0P of the former ; or, in other words, the vertical and one lateral axis (ab) of marcasite coincide with two principal axes of pyrites.

(2) The vertical axis of marcasite is parallel with a principal axis of pyrites; the braehydiagonal axis is parallel with a diagonal axis of pyrites.

Kynance Cove lies in the midst of a Serpentine District. The Serpentine is associated with some little hornblende schist in the cove, and is traversed by black dykes both porphyritic and non-porphyritic from a few inches to several feet thick, by granitic veins, as also by veins of saussuritic gabbro, which latter are, however, of rare occun'ence on the western side of the Lizard.

When looking due east from the middle of Kynanee Sands a rectangular block of white rock is seen in the dark red serpentine cliff from 70 to 80 ft. above the sea-level at low water, and about 200 yds. from the spectator. The vein that gives rise to this block can be easily reached by crossing the stream that enters the cove from the east, climbing the rising ground, and after reaching a ridge about 100 yds. from the stream, descending the grassy slope to the right to a point about 9.00 yds. south-east of Oliver's Refreshment House. Here, a few feet below the grass, a block of rock is seen 4 ft. high, 6 ft. through in front, and covered by broken serpentine behind.

Although all the modes of hemihedrism possible in the cubic system have been found to occur among minerals, no mineral l~elonging to that system has yet been proved to be tetartohedral like sodium chlorate, and the nitrates of barium, strontium and lead.

There has, however, been some evidence in favour of the tetartohedral character of Ullmannite since the examination of the crystals from Lölling in Carinthia, and those from Sarrabus in Sardinia. The former were found by Zepharovieh to be distinctly tetrahedral in form and habit, the latter were found by Klein to be distinctly pyritohedral. Zepharorich found the specific gravity of the Lölling Ullmannite to be 6·72, while Klein found that of the Sardinian crystals to be 6·803-6·883, and for this reason it was at first thought that the two occurrences might be different modifications of the antimono-sulphide of nickel; there was also considerable discrepancy between the two analyses.

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.

In a paper in Zts. f. Kryst. IX. 186, Professor Laspeyres states that the yellow enerustation uponFelsSbanya stibnite is not ecrvantite, but a sulphide of zinc, which he determines to be wurtzite, chiefly on the optical ground that a black interference cross was observed between crossed nicols, for the chemical proof based on the solubility in cold concentrated hydrochloric acid can hardly be regarded as very conclusive, considering the fact that he had no true wurtzite with which to make the comparison, but only so-called schalenblende, spiauterite, etc. On this account it seemed desirable to test the solubility of wurtzite in HCl, and accordingly a series of experiments as to the comparative solubility of wurtzite, spiauterite, voltzite and different varieties of blende was made by treating small fragments with cold concentrated HCl, (as was done by Professor Laspeyres) in small tubes, in the mouth of which strips of lead acetate paper were inserted.

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.

Two large masses of meteoric iron, which have been removed from Tucson, are now preserved, the one at Washington, the other at San Francisco. According to Lippincott's Gazetteers Tucson is "a posttown, capital of Pima County, Arizona, U.S.A., on the Rio Santa Cruz, and on the Southern Pacific Railroad, about 250 miles east of Yuma. It was founded in the year 1560 by the Jesuits. It contains a church, the Institute of St. Joseph, two free schools, a bank, a newspaper office, a court-house, a United States depository, many stores, and two flour mills. The population in 1880 was 7,007."

This instrument, which was designed for use in the Crystallographic Laboratory of the City and Guilds of London Institute (Central Institution), is in its simplest form (Plate III.) a strong and inexpensive Wollaston Goniometer. It is, however, constructed in such a way that it may be converted into an instrument of greater precision (Plates IV. V.) by the simple addition of accessory parts to tho apparatus of Plate III. without any previous alteration.

L is the graduated disc, and B the milled head by which it is turned; the vernier v is not the slender tongue of metal which is usual in such instruments, but is engraved upon a portion of the fixed disc V; and L is kept in continual contact with V by means of a circular steel spring inserted between B and the bearing of the axle.

Fresnel's representation of the laws of transmission of rays of light in biaxal crystals, by reference to the surface distinguished by his nsane, has long been regarded as one of the greatest achievements in the domain of Physical Science. In his memoir on Double Refraction, Fresnel proceeded as follows :—

1. He assumed that the transmission of a ray of light is effected by means of an elastic ether vibrating transversely to its direction.

To the ether is thus assigned a property not belonging to a perfectly fluid body in a state of rest : perfect fluidity of a body at rest involves incapacity of resistance to mere change of shape, and it is to such distortional resistance that transverse vibrations must be due.

The existence in the British Isles of a rock essentially composed of garnet and omphacite, and answering therefore to Hauy's' definition of eclogite, does not appear to have been hitherto recorded.

The following description of such a rock from Totig Ferry, Loch Dutch, is therefore of some interest. The specimen was collected by the Director General, who informs me that he believes it to be a part of the Archæan gneiss which in the region of Loch Alsh and Loch Carron has been thrust bodily from the east over the Torridon sandstone.

The rock is of a dull green eolour, and contains numerous reddishbrown garnets. Under the microscope the principal constituents are seen to be garnet and omphacite—a pale green pyroxene without any definite crystalline form. Green hornblende, plagioclase, rutile, ironores, quartz, and epidote occur as accessories.

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.